Manifest V3 Compatibility Tests

This project is a self-contained Manifest V3 (MV3) Webextension that tests the extension APIs available in supported browsers against some expectations of how these APIs should behave. These expectations are largely based on the current Chrome Extension API Documentation, and the current defacto standard implementation in Chrome.

The purpose of this project is to document API differences across browsers, both for other extension developers, and to encourage convergence to consistent and compatbility Webextension API implementations.

Try it out

You can load this extension in MV3 compatible browsers as follows:

Chrome (and other Chrome-based browsers)

1. Open chrome://extensions/.
2. Toggle 'Developer mode' in the top right corner.
3. Click 'Load unpacked', navigate to the mv3-compat-tests/Shared (Extension)/Resources/ folder, and chose select.
4. The tests should automatically open and start running. The test page can also be re-opened by clicking the extension's action icon.

Safari

1. Open mv3-compat-tests.xcodeproj in Xcode.
2. Run mv3-compat-tests (macOS) target.
3. Go to Safari settings -> Extensions and enable mv3-compat-tests.
4. Click Edit Websites... and grant permissions for all websites to the extension.
5. If the tests don't open automatically, click the extension's action icon to start them.

Firefox

1. Edit manifest.json, adding "scripts": ["background.js"] underneath the service_worker line.
2. Navigate to about:debugging
3. Click 'Load Temporary Add-on...' and navigate to the mv3-compat-tests/Shared (Extension)/Resources/ folder and select manifest.json.
4. Go to about:addons, find 'mv3-compat-tests', click on the '...' menu and select 'Manage'.
5. Go to the 'Permissions' tab and check 'Access your data for all websites' under Optional permissions.
6. Go back to about:debugging and click the 'Manifest URL' link. On that page, change the path to test.html.

Test status

The tests currently cover parts of the scripting and declarativeNetRequest APIs that are relevant to the duckduckgo-privacy-extension. The purpose is to surface issues we've found testing MV3 APIs across platforms.

Results

Current status table (only failing tests shown):

Test	Chrome 110	Safari 17.2	Safari Tech Preview 188	Firefox Nightly 122
scripting.executeScript: Returns an array of InjectionResult	✅	✅ (fixed in Safari 17)1	✅	❌
scripting.registerContentScripts: Can register content-scripts at document_start	✅	✅ (fixed in Safari 17)2	✅	❌3
declarativeNetRequest: requestDomains condition triggers on matched domains	✅	❌4	❌	❌3
declarativeNetRequest: allowAllRequests disables static blocking rules when document URL matches	✅	✅ (fixed in Safari 17.2)	✅	❌3
declarativeNetRequest: allowAllRequests rules work when removeRuleIds is used in the same updateDynamicRules call	✅	✅	✅	❌3
declarativeNetRequest: redirect to extension image url with anchored urlFilter	✅	✅	✅	❌
declarativeNetRequest: queryTransform can add search parameters in main_frame requests	✅	❌	❌	✅
declarativeNetRequest: modifyHeaders can add a Sec-GPC header	✅	❌5	❌	✅
declarativeNetRequest: 'initiatorDomains' condition limits matches to requests initiated by matching domain	✅	❌6	❌	❌3
declarativeNetRequest: 'initiatorDomains' condition list matches initators' subdomains	✅	❌[^8]	❌	❌3
declarativeNetRequest: 'domains' condition list matches initators' subdomains	✅	✅	✅	❌7
declarativeNetRequest: redirect supports regexSubstitution	✅	❌	❌	✅

Footnotes

1. This failure is due to this API not returning the result of func, the function passed to the script injection back to the background context. Instead, an array of null is returned. ↩

2. "chrome.scripting.registerContentScripts is not a function". This API is not yet implemented in Safari 16.3. ↩

3. world parameter of scripting.registerContentScripts is not supported in Firefox - this prevents many other tests from running, as we use a content-script as part of the test-suite. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

4. Rules using the requestDomains condition are not supported. ↩

5. Invalid call to declarativeNetRequest.updateDynamicRules(). Error with rule at index 0: Rule with id 5 is invalid. modifyHeaders is not a supported action type". modifyHeaders is not supported. ↩

6. This option is only supported under the legacy 'domains' property. ↩

7. domains condition for DNR is not supported in Firefox. ↩