diff --git a/packages/react-debug-tools/src/__tests__/ReactHooksInspectionIntegration-test.js b/packages/react-debug-tools/src/__tests__/ReactHooksInspectionIntegration-test.js
index 5b36039ecc5dc..f5003e96bdf6c 100644
--- a/packages/react-debug-tools/src/__tests__/ReactHooksInspectionIntegration-test.js
+++ b/packages/react-debug-tools/src/__tests__/ReactHooksInspectionIntegration-test.js
@@ -614,7 +614,7 @@ describe('ReactHooksInspectionIntegration', () => {
     expect(tree[0].id).toEqual(0);
     expect(tree[0].isStateEditable).toEqual(false);
     expect(tree[0].name).toEqual('Id');
-    expect(String(tree[0].value).startsWith('r:')).toBe(true);
+    expect(String(tree[0].value).startsWith(':r')).toBe(true);
 
     expect(tree[1]).toEqual({
       id: 1,
diff --git a/packages/react-dom/src/__tests__/ReactDOMUseId-test.js b/packages/react-dom/src/__tests__/ReactDOMUseId-test.js
index 036c138d5e97a..41c4ddcbcc489 100644
--- a/packages/react-dom/src/__tests__/ReactDOMUseId-test.js
+++ b/packages/react-dom/src/__tests__/ReactDOMUseId-test.js
@@ -93,7 +93,11 @@ describe('useId', () => {
   }
 
   function normalizeTreeIdForTesting(id) {
-    const [serverClientPrefix, base32, hookIndex] = id.split(':');
+    const result = id.match(/:(R|r)(.*):(([0-9]*):)?/);
+    if (result === undefined) {
+      throw new Error('Invalid id format');
+    }
+    const [, serverClientPrefix, base32, hookIndex] = result;
     if (serverClientPrefix.endsWith('r')) {
       // Client ids aren't stable. For testing purposes, strip out the counter.
       return (
@@ -278,7 +282,7 @@ describe('useId', () => {
     // 'R:' prefix, and the first character after that, which may not correspond
     // to a complete set of 5 bits.
     //
-    // Example: R:clalalalalalalala...
+    // Example: :Rclalalalalalalala...:
     //
     // We can use this pattern to test large ids that exceed the bitwise
     // safe range (32 bits). The algorithm should theoretically support ids
@@ -313,8 +317,8 @@ describe('useId', () => {
 
     // Confirm that every id matches the expected pattern
     for (let i = 0; i < divs.length; i++) {
-      // Example: R:clalalalalalalala...
-      expect(divs[i].id).toMatch(/^R:.(((al)*a?)((la)*l?))*$/);
+      // Example: :Rclalalalalalalala...:
+      expect(divs[i].id).toMatch(/^:R.(((al)*a?)((la)*l?))*:$/);
     }
   });
 
@@ -338,7 +342,7 @@ describe('useId', () => {
       <div
         id="container"
       >
-        R:0, R:0:1, R:0:2
+        :R0:, :R0:1:, :R0:2:
         <!-- -->
       </div>
     `);
@@ -364,7 +368,7 @@ describe('useId', () => {
       <div
         id="container"
       >
-        R:0
+        :R0:
         <!-- -->
       </div>
     `);
@@ -603,10 +607,10 @@ describe('useId', () => {
         id="container"
       >
         <div>
-          custom-prefix-R:1
+          :custom-prefix-R1:
         </div>
         <div>
-          custom-prefix-R:2
+          :custom-prefix-R2:
         </div>
       </div>
     `);
@@ -620,13 +624,13 @@ describe('useId', () => {
         id="container"
       >
         <div>
-          custom-prefix-R:1
+          :custom-prefix-R1:
         </div>
         <div>
-          custom-prefix-R:2
+          :custom-prefix-R2:
         </div>
         <div>
-          custom-prefix-r:0
+          :custom-prefix-r0:
         </div>
       </div>
     `);
diff --git a/packages/react-dom/src/server/ReactDOMServerFormatConfig.js b/packages/react-dom/src/server/ReactDOMServerFormatConfig.js
index 20887c226015a..f623556bb62de 100644
--- a/packages/react-dom/src/server/ReactDOMServerFormatConfig.js
+++ b/packages/react-dom/src/server/ReactDOMServerFormatConfig.js
@@ -130,7 +130,7 @@ export function createResponseState(
     placeholderPrefix: stringToPrecomputedChunk(idPrefix + 'P:'),
     segmentPrefix: stringToPrecomputedChunk(idPrefix + 'S:'),
     boundaryPrefix: idPrefix + 'B:',
-    idPrefix: idPrefix + 'R:',
+    idPrefix: idPrefix,
     nextSuspenseID: 0,
     sentCompleteSegmentFunction: false,
     sentCompleteBoundaryFunction: false,
@@ -242,13 +242,13 @@ export function makeId(
 ): string {
   const idPrefix = responseState.idPrefix;
 
-  let id = idPrefix + treeId;
+  let id = ':' + idPrefix + 'R' + treeId + ':';
 
   // Unless this is the first id at this level, append a number at the end
   // that represents the position of this useId hook among all the useId
   // hooks for this fiber.
   if (localId > 0) {
-    id += ':' + localId.toString(32);
+    id += localId.toString(32) + ':';
   }
 
   return id;
diff --git a/packages/react-reconciler/src/ReactFiberHooks.new.js b/packages/react-reconciler/src/ReactFiberHooks.new.js
index 3f64a7d8f9178..5c4b9357f909e 100644
--- a/packages/react-reconciler/src/ReactFiberHooks.new.js
+++ b/packages/react-reconciler/src/ReactFiberHooks.new.js
@@ -2072,19 +2072,19 @@ function mountId(): string {
     const treeId = getTreeId();
 
     // Use a captial R prefix for server-generated ids.
-    id = identifierPrefix + 'R:' + treeId;
+    id = ':' + identifierPrefix + 'R' + treeId + ':';
 
     // Unless this is the first id at this level, append a number at the end
     // that represents the position of this useId hook among all the useId
     // hooks for this fiber.
     const localId = localIdCounter++;
     if (localId > 0) {
-      id += ':' + localId.toString(32);
+      id += localId.toString(32) + ':';
     }
   } else {
     // Use a lowercase r prefix for client-generated ids.
     const globalClientId = globalClientIdCounter++;
-    id = identifierPrefix + 'r:' + globalClientId.toString(32);
+    id = ':' + identifierPrefix + 'r' + globalClientId.toString(32) + ':';
   }
 
   hook.memoizedState = id;
diff --git a/packages/react-reconciler/src/ReactFiberHooks.old.js b/packages/react-reconciler/src/ReactFiberHooks.old.js
index d55cac9b26c74..f0fcef733d581 100644
--- a/packages/react-reconciler/src/ReactFiberHooks.old.js
+++ b/packages/react-reconciler/src/ReactFiberHooks.old.js
@@ -2072,19 +2072,19 @@ function mountId(): string {
     const treeId = getTreeId();
 
     // Use a captial R prefix for server-generated ids.
-    id = identifierPrefix + 'R:' + treeId;
+    id = ':' + identifierPrefix + 'R' + treeId + ':';
 
     // Unless this is the first id at this level, append a number at the end
     // that represents the position of this useId hook among all the useId
     // hooks for this fiber.
     const localId = localIdCounter++;
     if (localId > 0) {
-      id += ':' + localId.toString(32);
+      id += localId.toString(32) + ':';
     }
   } else {
     // Use a lowercase r prefix for client-generated ids.
     const globalClientId = globalClientIdCounter++;
-    id = identifierPrefix + 'r:' + globalClientId.toString(32);
+    id = ':' + identifierPrefix + 'r' + globalClientId.toString(32) + ':';
   }
 
   hook.memoizedState = id;