diff --git a/packages/browser/src/backend.ts b/packages/browser/src/backend.ts
index 89cf843d48ae..2543c6ae99ad 100644
--- a/packages/browser/src/backend.ts
+++ b/packages/browser/src/backend.ts
@@ -8,6 +8,8 @@ import { FetchTransport, makeNewFetchTransport, makeNewXHRTransport, XHRTranspor
 /**
  * Configuration options for the Sentry Browser SDK.
  * @see BrowserClient for more information.
+ *
+ * TODO(v7): move to client
  */
 export interface BrowserOptions extends Options {
   /**
diff --git a/packages/browser/src/client.ts b/packages/browser/src/client.ts
index 75aab49db77b..b64997c0a23b 100644
--- a/packages/browser/src/client.ts
+++ b/packages/browser/src/client.ts
@@ -1,17 +1,20 @@
-import { BaseClient, Scope, SDK_VERSION } from '@sentry/core';
-import { Event, EventHint } from '@sentry/types';
-import { getGlobalObject, logger } from '@sentry/utils';
+import { BaseClient, getEnvelopeEndpointWithUrlEncodedAuth, initAPIDetails, Scope, SDK_VERSION } from '@sentry/core';
+import { Event, EventHint, Severity, Transport, TransportOptions } from '@sentry/types';
+import { getGlobalObject, logger, supportsFetch } from '@sentry/utils';
 
 import { BrowserBackend, BrowserOptions } from './backend';
+import { eventFromException, eventFromMessage } from './eventbuilder';
 import { IS_DEBUG_BUILD } from './flags';
 import { injectReportDialog, ReportDialogOptions } from './helpers';
 import { Breadcrumbs } from './integrations';
+import { FetchTransport, makeNewFetchTransport, makeNewXHRTransport, XHRTransport } from './transports';
 
 /**
  * The Sentry Browser SDK Client.
  *
  * @see BrowserOptions for documentation on configuration options.
  * @see SentryClient for usage documentation.
+ * TODO(v7): remove BrowserBackend
  */
 export class BrowserClient extends BaseClient<BrowserBackend, BrowserOptions> {
   /**
@@ -32,6 +35,7 @@ export class BrowserClient extends BaseClient<BrowserBackend, BrowserOptions> {
       version: SDK_VERSION,
     };
 
+    // TODO(v7): remove BrowserBackend param
     super(BrowserBackend, options);
   }
 
@@ -58,6 +62,20 @@ export class BrowserClient extends BaseClient<BrowserBackend, BrowserOptions> {
     });
   }
 
+  /**
+   * @inheritDoc
+   */
+  public eventFromException(exception: unknown, hint?: EventHint): PromiseLike<Event> {
+    return eventFromException(exception, hint, this._options.attachStacktrace);
+  }
+
+  /**
+   * @inheritDoc
+   */
+  public eventFromMessage(message: string, level: Severity = Severity.Info, hint?: EventHint): PromiseLike<Event> {
+    return eventFromMessage(message, level, hint, this._options.attachStacktrace);
+  }
+
   /**
    * @inheritDoc
    */
@@ -76,4 +94,40 @@ export class BrowserClient extends BaseClient<BrowserBackend, BrowserOptions> {
     }
     super._sendEvent(event);
   }
+
+  /**
+   * @inheritDoc
+   */
+  protected _setupTransport(): Transport {
+    if (!this._options.dsn) {
+      // We return the noop transport here in case there is no Dsn.
+      return super._setupTransport();
+    }
+
+    const transportOptions: TransportOptions = {
+      ...this._options.transportOptions,
+      dsn: this._options.dsn,
+      tunnel: this._options.tunnel,
+      sendClientReports: this._options.sendClientReports,
+      _metadata: this._options._metadata,
+    };
+
+    const api = initAPIDetails(transportOptions.dsn, transportOptions._metadata, transportOptions.tunnel);
+    const url = getEnvelopeEndpointWithUrlEncodedAuth(api.dsn, api.tunnel);
+
+    if (this._options.transport) {
+      return new this._options.transport(transportOptions);
+    }
+    if (supportsFetch()) {
+      const requestOptions: RequestInit = { ...transportOptions.fetchParameters };
+      this._newTransport = makeNewFetchTransport({ requestOptions, url });
+      return new FetchTransport(transportOptions);
+    }
+
+    this._newTransport = makeNewXHRTransport({
+      url,
+      headers: transportOptions.headers,
+    });
+    return new XHRTransport(transportOptions);
+  }
 }
diff --git a/packages/browser/src/exports.ts b/packages/browser/src/exports.ts
index b4dd4374a7b3..2a62e8e46fbe 100644
--- a/packages/browser/src/exports.ts
+++ b/packages/browser/src/exports.ts
@@ -41,6 +41,7 @@ export {
   withScope,
 } from '@sentry/core';
 
+// TODO(v7): refactor to use client here!
 export { BrowserOptions } from './backend';
 export { BrowserClient } from './client';
 export { injectReportDialog, ReportDialogOptions } from './helpers';
diff --git a/packages/browser/test/unit/backend.test.ts b/packages/browser/test/unit/backend.test.ts
index 71ffec4d75b1..83f95307a8c7 100644
--- a/packages/browser/test/unit/backend.test.ts
+++ b/packages/browser/test/unit/backend.test.ts
@@ -2,6 +2,8 @@ import { BrowserBackend } from '../../src/backend';
 
 let backend: BrowserBackend;
 
+// TODO(v7): remove when deleting Backend
+
 describe('BrowserBackend', () => {
   describe('sendEvent()', () => {
     it('should use NoopTransport', () => {
diff --git a/packages/browser/test/unit/index.test.ts b/packages/browser/test/unit/index.test.ts
index 83c0053d3b66..707354fe7d1d 100644
--- a/packages/browser/test/unit/index.test.ts
+++ b/packages/browser/test/unit/index.test.ts
@@ -246,7 +246,7 @@ describe('SentryBrowser initialization', () => {
     it('should set SDK data when Sentry.init() is called', () => {
       init({ dsn });
 
-      const sdkData = (getCurrentHub().getClient() as any)._backend._transport._api.metadata?.sdk;
+      const sdkData = (getCurrentHub().getClient() as any).getTransport()._api.metadata?.sdk;
 
       expect(sdkData.name).toBe('sentry.javascript.browser');
       expect(sdkData.packages[0].name).toBe('npm:@sentry/browser');
@@ -257,7 +257,7 @@ describe('SentryBrowser initialization', () => {
     it('should set SDK data when instantiating a client directly', () => {
       const client = new BrowserClient({ dsn });
 
-      const sdkData = (client as any)._backend._transport._api.metadata?.sdk;
+      const sdkData = (client as any).getTransport()._api.metadata?.sdk;
 
       expect(sdkData.name).toBe('sentry.javascript.browser');
       expect(sdkData.packages[0].name).toBe('npm:@sentry/browser');
@@ -285,7 +285,7 @@ describe('SentryBrowser initialization', () => {
         },
       });
 
-      const sdkData = (getCurrentHub().getClient() as any)._backend._transport._api.metadata?.sdk;
+      const sdkData = (getCurrentHub().getClient() as any).getTransport()._api.metadata?.sdk;
 
       expect(sdkData.name).toBe('sentry.javascript.angular');
       expect(sdkData.packages[0].name).toBe('npm:@sentry/angular');
diff --git a/packages/browser/test/unit/integrations/linkederrors.test.ts b/packages/browser/test/unit/integrations/linkederrors.test.ts
index 1531aa6f77ed..35f54f4b2d87 100644
--- a/packages/browser/test/unit/integrations/linkederrors.test.ts
+++ b/packages/browser/test/unit/integrations/linkederrors.test.ts
@@ -34,6 +34,7 @@ describe('LinkedErrors', () => {
       one.cause = two;
 
       const originalException = one;
+      // TODO(v7): refactor to use client here!
       const backend = new BrowserBackend({});
       return backend.eventFromException(originalException).then(event => {
         const result = LinkedErrorsModule._handler('cause', 5, event, {
@@ -65,6 +66,7 @@ describe('LinkedErrors', () => {
 
       const originalException = one;
       const backend = new BrowserBackend({});
+      // TODO(v7): refactor to use client here!
       return backend.eventFromException(originalException).then(event => {
         const result = LinkedErrorsModule._handler('reason', 5, event, {
           originalException,
@@ -92,6 +94,7 @@ describe('LinkedErrors', () => {
 
       const backend = new BrowserBackend({});
       const originalException = one;
+      // TODO(v7): refactor to use client here!
       return backend.eventFromException(originalException).then(event => {
         const result = LinkedErrorsModule._handler('cause', 2, event, {
           originalException,
diff --git a/packages/core/src/baseclient.ts b/packages/core/src/baseclient.ts
index b7fef7f2164f..59145508ca9d 100644
--- a/packages/core/src/baseclient.ts
+++ b/packages/core/src/baseclient.ts
@@ -28,15 +28,21 @@ import {
   uuid4,
 } from '@sentry/utils';
 
+import { initAPIDetails } from './api';
 import { Backend, BackendClass } from './basebackend';
 import { IS_DEBUG_BUILD } from './flags';
 import { IntegrationIndex, setupIntegrations } from './integration';
+import { createEventEnvelope, createSessionEnvelope } from './request';
+import { NewTransport } from './transports/base';
+import { NoopTransport } from './transports/noop';
 
 const ALREADY_SEEN_ERROR = "Not capturing exception because it's already been captured.";
 
 /**
  * Base implementation for all JavaScript SDK clients.
  *
+ * TODO(v7): refactor doc w.r.t. Backend
+ *
  * Call the constructor with the corresponding backend constructor and options
  * specific to the client subclass. To access these options later, use
  * {@link Client.getOptions}. Also, the Backend instance is available via
@@ -71,6 +77,7 @@ export abstract class BaseClient<B extends Backend, O extends Options> implement
    * The backend used to physically interact in the environment. Usually, this
    * will correspond to the client. When composing SDKs, however, the Backend
    * from the root SDK will be used.
+   * TODO(v7): DELETE
    */
   protected readonly _backend: B;
 
@@ -86,6 +93,12 @@ export abstract class BaseClient<B extends Backend, O extends Options> implement
   /** Number of calls being processed */
   protected _numProcessing: number = 0;
 
+  /** Cached transport used internally. */
+  protected _transport: Transport;
+
+  /** New v7 Transport that is initialized alongside the old one */
+  protected _newTransport?: NewTransport;
+
   /**
    * Initializes this client instance.
    *
@@ -93,12 +106,17 @@ export abstract class BaseClient<B extends Backend, O extends Options> implement
    * @param options Options for the client.
    */
   protected constructor(backendClass: BackendClass<B, O>, options: O) {
+    // TODO(v7): Delete
     this._backend = new backendClass(options);
     this._options = options;
 
     if (options.dsn) {
       this._dsn = makeDsn(options.dsn);
+    } else {
+      IS_DEBUG_BUILD && logger.warn('No DSN provided, client will not do anything.');
     }
+
+    this._transport = this._setupTransport();
   }
 
   /**
@@ -115,8 +133,7 @@ export abstract class BaseClient<B extends Backend, O extends Options> implement
     let eventId: string | undefined = hint && hint.event_id;
 
     this._process(
-      this._getBackend()
-        .eventFromException(exception, hint)
+      this.eventFromException(exception, hint)
         .then(event => this._captureEvent(event, hint, scope))
         .then(result => {
           eventId = result;
@@ -133,8 +150,8 @@ export abstract class BaseClient<B extends Backend, O extends Options> implement
     let eventId: string | undefined = hint && hint.event_id;
 
     const promisedEvent = isPrimitive(message)
-      ? this._getBackend().eventFromMessage(String(message), level, hint)
-      : this._getBackend().eventFromException(message, hint);
+      ? this.eventFromMessage(String(message), level, hint)
+      : this.eventFromException(message, hint);
 
     this._process(
       promisedEvent
@@ -204,7 +221,7 @@ export abstract class BaseClient<B extends Backend, O extends Options> implement
    * @inheritDoc
    */
   public getTransport(): Transport {
-    return this._getBackend().getTransport();
+    return this._transport;
   }
 
   /**
@@ -249,6 +266,57 @@ export abstract class BaseClient<B extends Backend, O extends Options> implement
     }
   }
 
+  /**
+   * @inheritDoc
+   */
+  public sendEvent(event: Event): void {
+    // TODO(v7): Remove the if-else
+    if (
+      this._newTransport &&
+      this._options.dsn &&
+      this._options._experiments &&
+      this._options._experiments.newTransport
+    ) {
+      const api = initAPIDetails(this._options.dsn, this._options._metadata, this._options.tunnel);
+      const env = createEventEnvelope(event, api);
+      void this._newTransport.send(env).then(null, reason => {
+        IS_DEBUG_BUILD && logger.error('Error while sending event:', reason);
+      });
+    } else {
+      void this._transport.sendEvent(event).then(null, reason => {
+        IS_DEBUG_BUILD && logger.error('Error while sending event:', reason);
+      });
+    }
+  }
+
+  /**
+   * @inheritDoc
+   */
+  public sendSession(session: Session): void {
+    if (!this._transport.sendSession) {
+      IS_DEBUG_BUILD && logger.warn("Dropping session because custom transport doesn't implement sendSession");
+      return;
+    }
+
+    // TODO(v7): Remove the if-else
+    if (
+      this._newTransport &&
+      this._options.dsn &&
+      this._options._experiments &&
+      this._options._experiments.newTransport
+    ) {
+      const api = initAPIDetails(this._options.dsn, this._options._metadata, this._options.tunnel);
+      const [env] = createSessionEnvelope(session, api);
+      void this._newTransport.send(env).then(null, reason => {
+        IS_DEBUG_BUILD && logger.error('Error while sending session:', reason);
+      });
+    } else {
+      void this._transport.sendSession(session).then(null, reason => {
+        IS_DEBUG_BUILD && logger.error('Error while sending session:', reason);
+      });
+    }
+  }
+
   /** Updates existing session based on the provided event */
   protected _updateSessionFromEvent(session: Session, event: Event): void {
     let crashed = false;
@@ -283,8 +351,9 @@ export abstract class BaseClient<B extends Backend, O extends Options> implement
   }
 
   /** Deliver captured session to Sentry */
+  // TODO(v7): should this be deleted?
   protected _sendSession(session: Session): void {
-    this._getBackend().sendSession(session);
+    this.sendSession(session);
   }
 
   /**
@@ -317,7 +386,9 @@ export abstract class BaseClient<B extends Backend, O extends Options> implement
     });
   }
 
-  /** Returns the current backend. */
+  /** Returns the current backend.
+   * TODO(v7): DELETE
+   */
   protected _getBackend(): B {
     return this._backend;
   }
@@ -490,8 +561,9 @@ export abstract class BaseClient<B extends Backend, O extends Options> implement
    * Tells the backend to send this event
    * @param event The Sentry event to send
    */
+  // TODO(v7): refactor: get rid of method?
   protected _sendEvent(event: Event): void {
-    this._getBackend().sendEvent(event);
+    this.sendEvent(event);
   }
 
   /**
@@ -618,6 +690,24 @@ export abstract class BaseClient<B extends Backend, O extends Options> implement
       },
     );
   }
+
+  /**
+   * Sets up the transport so it can be used later to send requests.
+   */
+  protected _setupTransport(): Transport {
+    return new NoopTransport();
+  }
+
+  /**
+   * @inheritDoc
+   */
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any, @typescript-eslint/explicit-module-boundary-types
+  public abstract eventFromException(_exception: any, _hint?: EventHint): PromiseLike<Event>;
+
+  /**
+   * @inheritDoc
+   */
+  public abstract eventFromMessage(_message: string, _level?: Severity, _hint?: EventHint): PromiseLike<Event>;
 }
 
 /**
diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index b066724ce099..77018c2b4437 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -23,6 +23,7 @@ export {
   getReportDialogEndpoint,
 } from './api';
 export { BaseClient } from './baseclient';
+// TODO(v7): Delete!
 export { BackendClass, BaseBackend } from './basebackend';
 export { eventToSentryRequest, sessionToSentryRequest } from './request';
 export { initAndBind, ClientClass } from './sdk';
diff --git a/packages/core/test/lib/base.test.ts b/packages/core/test/lib/base.test.ts
index 5c978b0ee530..8a26bd51f116 100644
--- a/packages/core/test/lib/base.test.ts
+++ b/packages/core/test/lib/base.test.ts
@@ -3,7 +3,7 @@ import { Event, Span, Transport } from '@sentry/types';
 import { dsnToString, logger, SentryError, SyncPromise } from '@sentry/utils';
 
 import * as integrationModule from '../../src/integration';
-import { TestBackend } from '../mocks/backend';
+import { NoopTransport } from '../../src/transports/noop';
 import { TestClient } from '../mocks/client';
 import { TestIntegration } from '../mocks/integration';
 import { FakeTransport } from '../mocks/transport';
@@ -12,7 +12,7 @@ const PUBLIC_DSN = 'https://username@domain/123';
 // eslint-disable-next-line no-var
 declare var global: any;
 
-const backendEventFromException = jest.spyOn(TestBackend.prototype, 'eventFromException');
+const clientEventFromException = jest.spyOn(TestClient.prototype, 'eventFromException');
 const clientProcess = jest.spyOn(TestClient.prototype as any, '_process');
 
 jest.mock('@sentry/utils', () => {
@@ -55,8 +55,8 @@ jest.mock('@sentry/utils', () => {
 
 describe('BaseClient', () => {
   beforeEach(() => {
-    TestBackend.sendEventCalled = undefined;
-    TestBackend.instance = undefined;
+    TestClient.sendEventCalled = undefined;
+    TestClient.instance = undefined;
   });
 
   afterEach(() => {
@@ -98,14 +98,24 @@ describe('BaseClient', () => {
   });
 
   describe('getTransport()', () => {
-    test('returns the transport from backend', () => {
+    test('returns the transport from client', () => {
       expect.assertions(2);
 
       const options = { dsn: PUBLIC_DSN, transport: FakeTransport };
       const client = new TestClient(options);
 
       expect(client.getTransport()).toBeInstanceOf(FakeTransport);
-      expect(TestBackend.instance!.getTransport()).toBe(client.getTransport());
+      expect(TestClient.instance!.getTransport()).toBe(client.getTransport());
+    });
+
+    test('retruns NoopTransport when no transport is passed', () => {
+      expect.assertions(2);
+
+      const options = { dsn: PUBLIC_DSN };
+      const client = new TestClient(options);
+
+      expect(client.getTransport()).toBeInstanceOf(NoopTransport);
+      expect(TestClient.instance!.getTransport()).toBe(client.getTransport());
     });
   });
 
@@ -223,7 +233,7 @@ describe('BaseClient', () => {
 
       client.captureException(new Error('test exception'));
 
-      expect(TestBackend.instance!.event).toEqual(
+      expect(TestClient.instance!.event).toEqual(
         expect.objectContaining({
           environment: 'production',
           event_id: '42',
@@ -257,7 +267,7 @@ describe('BaseClient', () => {
         scope,
       );
 
-      expect(TestBackend.instance!.event).toEqual(
+      expect(TestClient.instance!.event).toEqual(
         expect.objectContaining({
           extra: {
             bar: 'wat',
@@ -284,7 +294,7 @@ describe('BaseClient', () => {
         scope,
       );
 
-      expect(TestBackend.instance!.event).toEqual(
+      expect(TestClient.instance!.event).toEqual(
         expect.objectContaining({
           extra: {
             bar: 'wat',
@@ -309,12 +319,12 @@ describe('BaseClient', () => {
       client.captureException(thrown);
 
       expect(thrown.__sentry_captured__).toBe(true);
-      expect(backendEventFromException).toHaveBeenCalledTimes(1);
+      expect(clientEventFromException).toHaveBeenCalledTimes(1);
 
       client.captureException(thrown);
 
       // `captureException` should bail right away this second time around and not get as far as calling this again
-      expect(backendEventFromException).toHaveBeenCalledTimes(1);
+      expect(clientEventFromException).toHaveBeenCalledTimes(1);
     });
   });
 
@@ -324,7 +334,7 @@ describe('BaseClient', () => {
 
       client.captureMessage('test message');
 
-      expect(TestBackend.instance!.event).toEqual(
+      expect(TestClient.instance!.event).toEqual(
         expect.objectContaining({
           environment: 'production',
           event_id: '42',
@@ -337,7 +347,7 @@ describe('BaseClient', () => {
 
     test('should call eventFromException if input to captureMessage is not a primitive', () => {
       const client = new TestClient({ dsn: PUBLIC_DSN });
-      const spy = jest.spyOn(TestBackend.instance!, 'eventFromException');
+      const spy = jest.spyOn(TestClient.instance!, 'eventFromException');
 
       client.captureMessage('foo');
       client.captureMessage(null as any);
@@ -371,7 +381,7 @@ describe('BaseClient', () => {
         scope,
       );
 
-      expect(TestBackend.instance!.event).toEqual(
+      expect(TestClient.instance!.event).toEqual(
         expect.objectContaining({
           extra: {
             bar: 'wat',
@@ -392,7 +402,7 @@ describe('BaseClient', () => {
 
       client.captureEvent({}, undefined, scope);
 
-      expect(TestBackend.instance!.event).toBeUndefined();
+      expect(TestClient.instance!.event).toBeUndefined();
     });
 
     test('skips without a Dsn', () => {
@@ -403,7 +413,7 @@ describe('BaseClient', () => {
 
       client.captureEvent({}, undefined, scope);
 
-      expect(TestBackend.instance!.event).toBeUndefined();
+      expect(TestClient.instance!.event).toBeUndefined();
     });
 
     test.each([
@@ -443,8 +453,8 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'message' }, undefined, scope);
 
-      expect(TestBackend.instance!.event!.message).toBe('message');
-      expect(TestBackend.instance!.event).toEqual(
+      expect(TestClient.instance!.event!.message).toBe('message');
+      expect(TestClient.instance!.event).toEqual(
         expect.objectContaining({
           environment: 'production',
           event_id: '42',
@@ -462,8 +472,8 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'message', timestamp: 1234 }, undefined, scope);
 
-      expect(TestBackend.instance!.event!.message).toBe('message');
-      expect(TestBackend.instance!.event).toEqual(
+      expect(TestClient.instance!.event!.message).toBe('message');
+      expect(TestClient.instance!.event).toEqual(
         expect.objectContaining({
           environment: 'production',
           event_id: '42',
@@ -481,7 +491,7 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'message' }, { event_id: 'wat' }, scope);
 
-      expect(TestBackend.instance!.event!).toEqual(
+      expect(TestClient.instance!.event!).toEqual(
         expect.objectContaining({
           environment: 'production',
           event_id: 'wat',
@@ -501,7 +511,7 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'message' }, undefined, scope);
 
-      expect(TestBackend.instance!.event!).toEqual(
+      expect(TestClient.instance!.event!).toEqual(
         expect.objectContaining({
           environment: 'production',
           event_id: '42',
@@ -522,7 +532,7 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'message' }, undefined, scope);
 
-      expect(TestBackend.instance!.event!).toEqual(
+      expect(TestClient.instance!.event!).toEqual(
         expect.objectContaining({
           environment: 'env',
           event_id: '42',
@@ -543,7 +553,7 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'message' }, undefined, scope);
 
-      expect(TestBackend.instance!.event!).toEqual(
+      expect(TestClient.instance!.event!).toEqual(
         expect.objectContaining({
           environment: undefined,
           event_id: '42',
@@ -564,7 +574,7 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'message' }, undefined, scope);
 
-      expect(TestBackend.instance!.event!).toEqual(
+      expect(TestClient.instance!.event!).toEqual(
         expect.objectContaining({
           environment: 'production',
           event_id: '42',
@@ -584,10 +594,10 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'message' }, undefined, scope);
 
-      expect(TestBackend.instance!.event!).toHaveProperty('event_id', '42');
-      expect(TestBackend.instance!.event!).toHaveProperty('message', 'message');
-      expect(TestBackend.instance!.event!).toHaveProperty('breadcrumbs');
-      expect(TestBackend.instance!.event!.breadcrumbs![0]).toHaveProperty('message', 'breadcrumb');
+      expect(TestClient.instance!.event!).toHaveProperty('event_id', '42');
+      expect(TestClient.instance!.event!).toHaveProperty('message', 'message');
+      expect(TestClient.instance!.event!).toHaveProperty('breadcrumbs');
+      expect(TestClient.instance!.event!.breadcrumbs![0]).toHaveProperty('message', 'breadcrumb');
     });
 
     test('limits previously saved breadcrumbs', () => {
@@ -601,8 +611,8 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'message' }, undefined, scope);
 
-      expect(TestBackend.instance!.event!.breadcrumbs).toHaveLength(1);
-      expect(TestBackend.instance!.event!.breadcrumbs![0].message).toEqual('2');
+      expect(TestClient.instance!.event!.breadcrumbs).toHaveLength(1);
+      expect(TestClient.instance!.event!.breadcrumbs![0].message).toEqual('2');
     });
 
     test('adds context data', () => {
@@ -616,7 +626,7 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'message' }, undefined, scope);
 
-      expect(TestBackend.instance!.event!).toEqual(
+      expect(TestClient.instance!.event!).toEqual(
         expect.objectContaining({
           environment: 'production',
           event_id: '42',
@@ -638,7 +648,7 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'message' }, undefined, scope);
 
-      expect(TestBackend.instance!.event!).toEqual(
+      expect(TestClient.instance!.event!).toEqual(
         expect.objectContaining({
           environment: 'production',
           event_id: '42',
@@ -655,7 +665,7 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'message' });
 
-      expect(TestBackend.instance!.event!.sdk).toEqual({
+      expect(TestClient.instance!.event!.sdk).toEqual({
         integrations: ['TestIntegration'],
       });
     });
@@ -698,7 +708,7 @@ describe('BaseClient', () => {
         user: fourLevelsObject,
       });
 
-      expect(TestBackend.instance!.event!).toEqual(
+      expect(TestClient.instance!.event!).toEqual(
         expect.objectContaining({
           breadcrumbs: [normalizedBreadcrumb, normalizedBreadcrumb, normalizedBreadcrumb],
           contexts: normalizedObject,
@@ -749,7 +759,7 @@ describe('BaseClient', () => {
         user: fourLevelsObject,
       });
 
-      expect(TestBackend.instance!.event!).toEqual(
+      expect(TestClient.instance!.event!).toEqual(
         expect.objectContaining({
           breadcrumbs: [normalizedBreadcrumb, normalizedBreadcrumb, normalizedBreadcrumb],
           contexts: normalizedObject,
@@ -805,7 +815,7 @@ describe('BaseClient', () => {
         user: fourLevelsObject,
       });
 
-      expect(TestBackend.instance!.event!).toEqual(
+      expect(TestClient.instance!.event!).toEqual(
         expect.objectContaining({
           breadcrumbs: [normalizedBreadcrumb, normalizedBreadcrumb, normalizedBreadcrumb],
           contexts: normalizedObject,
@@ -871,7 +881,7 @@ describe('BaseClient', () => {
       // event. The code can be restored to its original form (the commented-out line below) once that hack is
       // removed. See https://github.com/getsentry/sentry-javascript/pull/4425 and
       // https://github.com/getsentry/sentry-javascript/pull/4574
-      const capturedEvent = TestBackend.instance!.event!;
+      const capturedEvent = TestClient.instance!.event!;
       if (capturedEvent.sdkProcessingMetadata?.normalizeDepth) {
         if (Object.keys(capturedEvent.sdkProcessingMetadata).length === 1) {
           delete capturedEvent.sdkProcessingMetadata;
@@ -899,7 +909,7 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'hello' });
 
-      expect(TestBackend.instance!.event!.message).toBe('hello');
+      expect(TestClient.instance!.event!.message).toBe('hello');
     });
 
     test('calls beforeSend and uses the new one', () => {
@@ -910,7 +920,7 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'hello' });
 
-      expect(TestBackend.instance!.event!.message).toBe('changed1');
+      expect(TestClient.instance!.event!.message).toBe('changed1');
     });
 
     test('calls beforeSend and discards the event', () => {
@@ -923,7 +933,7 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'hello' });
 
-      expect(TestBackend.instance!.event).toBeUndefined();
+      expect(TestClient.instance!.event).toBeUndefined();
       expect(captureExceptionSpy).not.toBeCalled();
       expect(loggerErrorSpy).toBeCalledWith(new SentryError('`beforeSend` returned `null`, will not send event.'));
     });
@@ -940,7 +950,7 @@ describe('BaseClient', () => {
 
         client.captureEvent({ message: 'hello' });
 
-        expect(TestBackend.instance!.event).toBeUndefined();
+        expect(TestClient.instance!.event).toBeUndefined();
         expect(loggerErrorSpy).toBeCalledWith(
           new SentryError('`beforeSend` method has to return `null` or a valid event.'),
         );
@@ -964,7 +974,7 @@ describe('BaseClient', () => {
       client.captureEvent({ message: 'hello' });
       jest.runOnlyPendingTimers();
 
-      TestBackend.sendEventCalled = (event: Event) => {
+      TestClient.sendEventCalled = (event: Event) => {
         expect(event.message).toBe('hello');
       };
 
@@ -992,7 +1002,7 @@ describe('BaseClient', () => {
       client.captureEvent({ message: 'hello' });
       jest.runOnlyPendingTimers();
 
-      TestBackend.sendEventCalled = (event: Event) => {
+      TestClient.sendEventCalled = (event: Event) => {
         expect(event.message).toBe('changed2');
       };
 
@@ -1020,7 +1030,7 @@ describe('BaseClient', () => {
       client.captureEvent({ message: 'hello' });
       jest.runAllTimers();
 
-      expect(TestBackend.instance!.event).toBeUndefined();
+      expect(TestClient.instance!.event).toBeUndefined();
     });
 
     test('beforeSend gets access to a hint as a second argument', () => {
@@ -1031,8 +1041,8 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'hello' }, { data: 'someRandomThing' });
 
-      expect(TestBackend.instance!.event!.message).toBe('hello');
-      expect((TestBackend.instance!.event! as any).data).toBe('someRandomThing');
+      expect(TestClient.instance!.event!.message).toBe('hello');
+      expect((TestClient.instance!.event! as any).data).toBe('someRandomThing');
     });
 
     test('beforeSend records dropped events', () => {
@@ -1068,7 +1078,7 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'hello' }, {}, scope);
 
-      expect(TestBackend.instance!.event).toBeUndefined();
+      expect(TestClient.instance!.event).toBeUndefined();
       expect(captureExceptionSpy).not.toBeCalled();
       expect(loggerErrorSpy).toBeCalledWith(new SentryError('An event processor returned null, will not send event.'));
     });
@@ -1108,7 +1118,7 @@ describe('BaseClient', () => {
 
       client.captureEvent({ message: 'hello' }, {}, scope);
 
-      expect(TestBackend.instance!.event!.exception!.values![0]).toStrictEqual({ type: 'Error', value: 'sorry' });
+      expect(TestClient.instance!.event!.exception!.values![0]).toStrictEqual({ type: 'Error', value: 'sorry' });
       expect(captureExceptionSpy).toBeCalledWith(exception, {
         data: {
           __sentry__: true,
@@ -1249,7 +1259,7 @@ describe('BaseClient', () => {
       });
 
       const delay = 300;
-      const spy = jest.spyOn(TestBackend.instance!, 'eventFromMessage');
+      const spy = jest.spyOn(TestClient.instance!, 'eventFromMessage');
       spy.mockImplementationOnce(
         (message, level) =>
           new SyncPromise(resolve => {
@@ -1317,7 +1327,7 @@ describe('BaseClient', () => {
   });
 
   describe('captureSession()', () => {
-    test('sends sessions to the backend', () => {
+    test('sends sessions to the client', () => {
       expect.assertions(1);
 
       const client = new TestClient({ dsn: PUBLIC_DSN });
@@ -1325,7 +1335,7 @@ describe('BaseClient', () => {
 
       client.captureSession(session);
 
-      expect(TestBackend.instance!.session).toEqual(session);
+      expect(TestClient.instance!.session).toEqual(session);
     });
 
     test('skips when disabled', () => {
@@ -1336,7 +1346,7 @@ describe('BaseClient', () => {
 
       client.captureSession(session);
 
-      expect(TestBackend.instance!.session).toBeUndefined();
+      expect(TestClient.instance!.session).toBeUndefined();
     });
   });
 });
diff --git a/packages/core/test/mocks/backend.ts b/packages/core/test/mocks/backend.ts
index 48ddb0d9cc0c..a201bc8c0b68 100644
--- a/packages/core/test/mocks/backend.ts
+++ b/packages/core/test/mocks/backend.ts
@@ -1,14 +1,11 @@
 import { Session } from '@sentry/hub';
-import { Event, Options, Severity, Transport } from '@sentry/types';
+import { Event, Severity, Transport } from '@sentry/types';
 import { resolvedSyncPromise } from '@sentry/utils';
 
 import { BaseBackend } from '../../src/basebackend';
+import { TestOptions } from './client';
 
-export interface TestOptions extends Options {
-  test?: boolean;
-  mockInstallFailure?: boolean;
-  enableSend?: boolean;
-}
+// TODO: Delete whole file (?)
 
 export class TestBackend extends BaseBackend<TestOptions> {
   public static instance?: TestBackend;
diff --git a/packages/core/test/mocks/client.ts b/packages/core/test/mocks/client.ts
index 810328818eae..8c02ca30f5f3 100644
--- a/packages/core/test/mocks/client.ts
+++ b/packages/core/test/mocks/client.ts
@@ -1,14 +1,80 @@
+import { Session } from '@sentry/hub';
+import { Event, Options, Severity, Transport } from '@sentry/types';
+import { resolvedSyncPromise } from '@sentry/utils';
+
 import { BaseClient } from '../../src/baseclient';
 import { initAndBind } from '../../src/sdk';
-import { TestBackend, TestOptions } from './backend';
+import { TestBackend } from './backend';
+export interface TestOptions extends Options {
+  test?: boolean;
+  mockInstallFailure?: boolean;
+  enableSend?: boolean;
+}
 
+// TODO(v7): remove TestBackend
 export class TestClient extends BaseClient<TestBackend, TestOptions> {
   public static instance?: TestClient;
+  public static sendEventCalled?: (event: Event) => void;
+
+  public event?: Event;
+  public session?: Session;
 
   public constructor(options: TestOptions) {
+    // TODO(v7): remove TestBackend param
     super(TestBackend, options);
     TestClient.instance = this;
   }
+
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any, @typescript-eslint/explicit-module-boundary-types
+  public eventFromException(exception: any): PromiseLike<Event> {
+    return resolvedSyncPromise({
+      exception: {
+        values: [
+          {
+            /* eslint-disable @typescript-eslint/no-unsafe-member-access */
+            type: exception.name,
+            value: exception.message,
+            /* eslint-enable @typescript-eslint/no-unsafe-member-access */
+          },
+        ],
+      },
+    });
+  }
+
+  public eventFromMessage(message: string, level: Severity = Severity.Info): PromiseLike<Event> {
+    return resolvedSyncPromise({ message, level });
+  }
+
+  public sendEvent(event: Event): void {
+    this.event = event;
+    if (this._options.enableSend) {
+      super.sendEvent(event);
+      return;
+    }
+    // eslint-disable-next-line @typescript-eslint/no-unused-expressions
+    TestClient.sendEventCalled && TestClient.sendEventCalled(event);
+  }
+
+  public sendSession(session: Session): void {
+    this.session = session;
+  }
+
+  protected _setupTransport(): Transport {
+    if (!this._options.dsn) {
+      // We return the noop transport here in case there is no Dsn.
+      return super._setupTransport();
+    }
+
+    const transportOptions = this._options.transportOptions
+      ? this._options.transportOptions
+      : { dsn: this._options.dsn };
+
+    if (this._options.transport) {
+      return new this._options.transport(transportOptions);
+    }
+
+    return super._setupTransport();
+  }
 }
 
 export function init(options: TestOptions): void {
diff --git a/packages/node/src/client.ts b/packages/node/src/client.ts
index dde7f8941b74..0b2b585edc5d 100644
--- a/packages/node/src/client.ts
+++ b/packages/node/src/client.ts
@@ -1,10 +1,12 @@
-import { BaseClient, Scope, SDK_VERSION } from '@sentry/core';
+import { BaseClient, getEnvelopeEndpointWithUrlEncodedAuth, initAPIDetails, Scope, SDK_VERSION } from '@sentry/core';
 import { SessionFlusher } from '@sentry/hub';
-import { Event, EventHint } from '@sentry/types';
-import { logger } from '@sentry/utils';
+import { Event, EventHint, Severity, Transport, TransportOptions } from '@sentry/types';
+import { logger, makeDsn, resolvedSyncPromise } from '@sentry/utils';
 
 import { NodeBackend } from './backend';
+import { eventFromMessage, eventFromUnknownInput } from './eventbuilder';
 import { IS_DEBUG_BUILD } from './flags';
+import { HTTPSTransport, HTTPTransport, makeNodeTransport } from './transports';
 import { NodeOptions } from './types';
 
 /**
@@ -12,6 +14,8 @@ import { NodeOptions } from './types';
  *
  * @see NodeOptions for documentation on configuration options.
  * @see SentryClient for usage documentation.
+ *
+ * TODO(v7): remove NodeBackend
  */
 export class NodeClient extends BaseClient<NodeBackend, NodeOptions> {
   protected _sessionFlusher: SessionFlusher | undefined;
@@ -33,6 +37,7 @@ export class NodeClient extends BaseClient<NodeBackend, NodeOptions> {
       version: SDK_VERSION,
     };
 
+    // TODO(v7): remove NodeBackend param
     super(NodeBackend, options);
   }
 
@@ -106,6 +111,21 @@ export class NodeClient extends BaseClient<NodeBackend, NodeOptions> {
     }
   }
 
+  /**
+   * @inheritDoc
+   */
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any, @typescript-eslint/explicit-module-boundary-types
+  public eventFromException(exception: any, hint?: EventHint): PromiseLike<Event> {
+    return resolvedSyncPromise(eventFromUnknownInput(exception, hint));
+  }
+
+  /**
+   * @inheritDoc
+   */
+  public eventFromMessage(message: string, level: Severity = Severity.Info, hint?: EventHint): PromiseLike<Event> {
+    return resolvedSyncPromise(eventFromMessage(message, level, hint, this._options.attachStacktrace));
+  }
+
   /**
    * @inheritDoc
    */
@@ -128,4 +148,45 @@ export class NodeClient extends BaseClient<NodeBackend, NodeOptions> {
       this._sessionFlusher.incrementSessionStatusCount();
     }
   }
+
+  /**
+   * @inheritDoc
+   */
+  protected _setupTransport(): Transport {
+    if (!this._options.dsn) {
+      // We return the noop transport here in case there is no Dsn.
+      return super._setupTransport();
+    }
+
+    const dsn = makeDsn(this._options.dsn);
+
+    const transportOptions: TransportOptions = {
+      ...this._options.transportOptions,
+      ...(this._options.httpProxy && { httpProxy: this._options.httpProxy }),
+      ...(this._options.httpsProxy && { httpsProxy: this._options.httpsProxy }),
+      ...(this._options.caCerts && { caCerts: this._options.caCerts }),
+      dsn: this._options.dsn,
+      tunnel: this._options.tunnel,
+      _metadata: this._options._metadata,
+    };
+
+    if (this._options.transport) {
+      return new this._options.transport(transportOptions);
+    }
+
+    const api = initAPIDetails(transportOptions.dsn, transportOptions._metadata, transportOptions.tunnel);
+    const url = getEnvelopeEndpointWithUrlEncodedAuth(api.dsn, api.tunnel);
+
+    this._newTransport = makeNodeTransport({
+      url,
+      headers: transportOptions.headers,
+      proxy: transportOptions.httpProxy,
+      caCerts: transportOptions.caCerts,
+    });
+
+    if (dsn.protocol === 'http') {
+      return new HTTPTransport(transportOptions);
+    }
+    return new HTTPSTransport(transportOptions);
+  }
 }
diff --git a/packages/node/src/index.ts b/packages/node/src/index.ts
index 9f65c3f1a1a8..48bb88a24872 100644
--- a/packages/node/src/index.ts
+++ b/packages/node/src/index.ts
@@ -42,6 +42,7 @@ export {
 } from '@sentry/core';
 
 export { NodeOptions } from './types';
+// TODO(v7): delete!
 export { NodeBackend } from './backend';
 export { NodeClient } from './client';
 export { defaultIntegrations, init, lastEventId, flush, close, getSentryRelease } from './sdk';
diff --git a/packages/node/test/index.test.ts b/packages/node/test/index.test.ts
index 0af38dae80fb..687465802a94 100644
--- a/packages/node/test/index.test.ts
+++ b/packages/node/test/index.test.ts
@@ -15,7 +15,6 @@ import {
   NodeClient,
   Scope,
 } from '../src';
-import { NodeBackend } from '../src/backend';
 import { ContextLines, LinkedErrors } from '../src/integrations';
 
 jest.mock('@sentry/core', () => {
@@ -78,7 +77,7 @@ describe('SentryNode', () => {
     let s: jest.SpyInstance<void, Event[]>;
 
     beforeEach(() => {
-      s = jest.spyOn(NodeBackend.prototype, 'sendEvent').mockImplementation(async () => Promise.resolve({ code: 200 }));
+      s = jest.spyOn(NodeClient.prototype, 'sendEvent').mockImplementation(async () => Promise.resolve({ code: 200 }));
     });
 
     afterEach(() => {
@@ -107,7 +106,7 @@ describe('SentryNode', () => {
     let s: jest.SpyInstance<void, Event[]>;
 
     beforeEach(() => {
-      s = jest.spyOn(NodeBackend.prototype, 'sendEvent').mockImplementation(async () => Promise.resolve({ code: 200 }));
+      s = jest.spyOn(NodeClient.prototype, 'sendEvent').mockImplementation(async () => Promise.resolve({ code: 200 }));
     });
 
     afterEach(() => {
@@ -360,7 +359,7 @@ describe('SentryNode initialization', () => {
       init({ dsn });
 
       // eslint-disable-next-line @typescript-eslint/no-explicit-any
-      const sdkData = (getCurrentHub().getClient() as any)._backend._transport._api.metadata?.sdk;
+      const sdkData = (getCurrentHub().getClient() as any).getTransport()._api.metadata?.sdk;
 
       expect(sdkData.name).toEqual('sentry.javascript.node');
       expect(sdkData.packages[0].name).toEqual('npm:@sentry/node');
@@ -372,7 +371,7 @@ describe('SentryNode initialization', () => {
       const client = new NodeClient({ dsn });
 
       // eslint-disable-next-line @typescript-eslint/no-explicit-any
-      const sdkData = (client as any)._backend._transport._api.metadata?.sdk;
+      const sdkData = (client as any).getTransport()._api.metadata?.sdk;
 
       expect(sdkData.name).toEqual('sentry.javascript.node');
       expect(sdkData.packages[0].name).toEqual('npm:@sentry/node');
@@ -401,7 +400,7 @@ describe('SentryNode initialization', () => {
       });
 
       // eslint-disable-next-line @typescript-eslint/no-explicit-any
-      const sdkData = (getCurrentHub().getClient() as any)._backend._transport._api.metadata?.sdk;
+      const sdkData = (getCurrentHub().getClient() as any).getTransport()._api.metadata?.sdk;
 
       expect(sdkData.name).toEqual('sentry.javascript.serverless');
       expect(sdkData.packages[0].name).toEqual('npm:@sentry/serverless');
diff --git a/packages/node/test/integrations/linkederrors.test.ts b/packages/node/test/integrations/linkederrors.test.ts
index 7dcaf077e4c6..8363bd177359 100644
--- a/packages/node/test/integrations/linkederrors.test.ts
+++ b/packages/node/test/integrations/linkederrors.test.ts
@@ -28,6 +28,7 @@ describe('LinkedErrors', () => {
       expect.assertions(2);
       const spy = jest.spyOn(linkedErrors, '_walkErrorTree');
       const one = new Error('originalException');
+      // TODO(v7): refactor to use client here!
       const backend = new NodeBackend({});
       let event: Event | undefined;
       return backend
@@ -52,6 +53,7 @@ describe('LinkedErrors', () => {
       );
       const one = new Error('originalException');
       const backend = new NodeBackend({});
+      // TODO(v7): refactor to use client here!
       return backend.eventFromException(one).then(event =>
         linkedErrors
           ._handler(event, {
@@ -72,6 +74,7 @@ describe('LinkedErrors', () => {
       two.cause = three;
 
       const backend = new NodeBackend({});
+      // TODO(v7): refactor to use client here!
       return backend.eventFromException(one).then(event =>
         linkedErrors
           ._handler(event, {
@@ -105,6 +108,7 @@ describe('LinkedErrors', () => {
       two.reason = three;
 
       const backend = new NodeBackend({});
+      // TODO(v7): refactor to use client here!
       return backend.eventFromException(one).then(event =>
         linkedErrors
           ._handler(event, {
@@ -138,6 +142,7 @@ describe('LinkedErrors', () => {
       two.cause = three;
 
       const backend = new NodeBackend({});
+      // TODO(v7): refactor to use client here!
       return backend.eventFromException(one).then(event =>
         linkedErrors
           ._handler(event, {
diff --git a/packages/types/src/client.ts b/packages/types/src/client.ts
index 69f7298105b2..e11950487fa1 100644
--- a/packages/types/src/client.ts
+++ b/packages/types/src/client.ts
@@ -60,7 +60,12 @@ export interface Client<O extends Options = Options> {
   /** Returns the current options. */
   getOptions(): O;
 
-  /** Returns clients transport. */
+  /**
+   * Returns the transport that is used by the client.
+   * Please note that the transport gets lazy initialized so it will only be there once the first event has been sent.
+   *
+   * @returns The transport.
+   */
   getTransport?(): Transport;
 
   /**
@@ -88,4 +93,17 @@ export interface Client<O extends Options = Options> {
 
   /** This is an internal function to setup all integrations that should run on the client */
   setupIntegrations(): void;
+
+  /** Creates an {@link Event} from all inputs to `captureException` and non-primitive inputs to `captureMessage`. */
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  eventFromException(exception: any, hint?: EventHint): PromiseLike<Event>;
+
+  /** Creates an {@link Event} from primitive inputs to `captureMessage`. */
+  eventFromMessage(message: string, level?: Severity, hint?: EventHint): PromiseLike<Event>;
+
+  /** Submits the event to Sentry */
+  sendEvent(event: Event): void;
+
+  /** Submits the session to Sentry */
+  sendSession(session: Session): void;
 }