# \#manifest-v3

**URL:** https://discourse.mozilla.org/tag/manifest-v3/126.md

[Latest](https://discourse.mozilla.org/latest.md) · [Categories](https://discourse.mozilla.org/categories.md) · [Tags](https://discourse.mozilla.org/tags.md)

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## [\[Showcase\] Building a Global Media Controller for Firefox (Proof-of-Concept)](https://discourse.mozilla.org/t/showcase-building-a-global-media-controller-for-firefox-proof-of-concept/148406)

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**Author:** [@MK2010GAMER](https://discourse.mozilla.org/u/MK2010GAMER)\
**Replies:** 2\
**Last updated:** [May 23, 2026, 2:51am UTC](https://discourse.mozilla.org/t/showcase-building-a-global-media-controller-for-firefox-proof-of-concept/148406 "2026-05-23T02:51:09Z")

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I’ve developed a lightweight extension to add a feature that Firefox currently completely lacks: a native, global media controller. The Problem: Firefox has no centralized, global UI for users to view or control media p…

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## [\[Firefox MV3\] Any plan to support scripting eval in "sandbox"?](https://discourse.mozilla.org/t/firefox-mv3-any-plan-to-support-scripting-eval-in-sandbox/147853)

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**Author:** [@cyfung1031](https://discourse.mozilla.org/u/cyfung1031)\
**Replies:** 2\
**Last updated:** [April 6, 2026, 7:02pm UTC](https://discourse.mozilla.org/t/firefox-mv3-any-plan-to-support-scripting-eval-in-sandbox/147853 "2026-04-06T19:02:09Z")

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In Chrome MV3, there is the sandbox feature that allowing JavaScript eval inside the sandbox page. "sandbox": { "pages": \[ "src/sandbox.html" \] }, "content\_security\_policy": { …

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## [\[EDITED\] Error: Permission denied to access property "then"](https://discourse.mozilla.org/t/edited-error-permission-denied-to-access-property-then/122836)

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**Author:** [@muwave](https://discourse.mozilla.org/u/muwave)\
**Replies:** 4\
**Last updated:** [November 18, 2025, 9:41am UTC](https://discourse.mozilla.org/t/edited-error-permission-denied-to-access-property-then/122836 "2025-11-18T09:41:03Z")

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I have a working mv3 chrome extension. When the content script receives a message it dispatches a custom event. The custom event is handled by a class that is injected in the target page window. Inject the class: windo…

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## [How do you debug issues related to going idle? (mv3)](https://discourse.mozilla.org/t/how-do-you-debug-issues-related-to-going-idle-mv3/142758)

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**Author:** [@bod](https://discourse.mozilla.org/u/bod)\
**Replies:** 4\
**Last updated:** [April 30, 2025, 6:11pm UTC](https://discourse.mozilla.org/t/how-do-you-debug-issues-related-to-going-idle-mv3/142758 "2025-04-30T18:11:33Z")

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Hi! My extension (which uses manifest v3) goes idle, which I understand is expected, but things go awry and I’m trying to understand exactly what, by adding lots of logs. But, alas, when the Developer Tools are open in…

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## [Manifest V3 validation tools?](https://discourse.mozilla.org/t/manifest-v3-validation-tools/102915)

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**Author:** [@tomr](https://discourse.mozilla.org/u/tomr)\
**Replies:** 4\
**Last updated:** [August 18, 2022, 10:13am UTC](https://discourse.mozilla.org/t/manifest-v3-validation-tools/102915 "2022-08-18T10:13:22Z")

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We’re in the process of making our extension fully V3 compliant (across Chrome, FF & Edge) which we know is going to require some big rewrites. Is anyone aware of any tools for validating V3 compliance (for any browser) …

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## [MV3 background scripts vs serviceworkers - MS/Edge didn't get the memo?](https://discourse.mozilla.org/t/mv3-background-scripts-vs-serviceworkers-ms-edge-didnt-get-the-memo/133613)

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**Author:** [@stig](https://discourse.mozilla.org/u/stig)\
**Replies:** 3\
**Last updated:** [July 16, 2024, 7:03am UTC](https://discourse.mozilla.org/t/mv3-background-scripts-vs-serviceworkers-ms-edge-didnt-get-the-memo/133613 "2024-07-16T07:03:37Z")

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I was happy when I learned about the initiative to make it possible declare both background.script and background.service\_worker in your webextension manifest.json file, and let the browser choose which to use. But some…

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## [Missing Context menus (mv3)](https://discourse.mozilla.org/t/missing-context-menus-mv3/133132)

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**Author:** [@ovarn](https://discourse.mozilla.org/u/ovarn)\
**Replies:** 7\
**Last updated:** [July 10, 2024, 6:02pm UTC](https://discourse.mozilla.org/t/missing-context-menus-mv3/133132 "2024-07-10T18:02:27Z")

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Hi everyone. I have an issue with the context menus created by me extension (manifest v3). Sometimes they just disappear. I found the workaround - manually trigger (e.g. disabling and enabling the extension) a service w…

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## [Allowing accessing data on all websites for group policy installations with Manifest V3](https://discourse.mozilla.org/t/allowing-accessing-data-on-all-websites-for-group-policy-installations-with-manifest-v3/131351)

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**Author:** [@karl3i](https://discourse.mozilla.org/u/karl3i)\
**Replies:** 7\
**Last updated:** [June 27, 2024, 11:15am UTC](https://discourse.mozilla.org/t/allowing-accessing-data-on-all-websites-for-group-policy-installations-with-manifest-v3/131351 "2024-06-27T11:15:07Z")

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We’re currently migrating our Manifest V2 extension to Manifest V3. Our extension enhances a large number of websites, so we ask the user to allow data for all websites. On Manifest V2, the manifest entry for that look…

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## [\[Blog post\] Manifest v3 in Firefox: Recap & Next Steps](https://discourse.mozilla.org/t/blog-post-manifest-v3-in-firefox-recap-next-steps/97372)

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**Author:** [@rob](https://discourse.mozilla.org/u/rob)\
**Replies:** 11\
**Last updated:** [June 14, 2024, 5:50pm UTC](https://discourse.mozilla.org/t/blog-post-manifest-v3-in-firefox-recap-next-steps/97372 "2024-06-14T17:50:54Z")

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It’s been about a year since our last update regarding Manifest v3. We have started an implementation of Manifest v3 and collaborated with other browser vendors in the WebExtension Community Group (WECG) to shape the fut…

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## [\[Blog post\] Manifest V3 Updates](https://discourse.mozilla.org/t/blog-post-manifest-v3-updates/130372)

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**Author:** [@Edward\_Sullivan](https://discourse.mozilla.org/u/Edward_Sullivan)\
**Replies:** 3\
**Last updated:** [June 14, 2024, 5:42pm UTC](https://discourse.mozilla.org/t/blog-post-manifest-v3-updates/130372 "2024-06-14T17:42:35Z")

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Hey All, posting this here in case folks haven’t seen our update from yesterday. Thank you. Ed

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## [Firefox InternalError (MV3)](https://discourse.mozilla.org/t/firefox-internalerror-mv3/130261)

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**Author:** [@stig](https://discourse.mozilla.org/u/stig)\
**Replies:** 5\
**Last updated:** [May 11, 2024, 3:18pm UTC](https://discourse.mozilla.org/t/firefox-internalerror-mv3/130261 "2024-05-11T15:18:55Z")

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So if you get a Firefox “InternalError” in browser-console when running your extension/contentscript on some sites, should you report a bug in bugzilla, or could it still be “your own” error? It’s complicated code (and …

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## [Post-MV3 versioning for "cross-browser" extensions?](https://discourse.mozilla.org/t/post-mv3-versioning-for-cross-browser-extensions/129819)

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**Author:** [@tomr](https://discourse.mozilla.org/u/tomr)\
**Replies:** 3\
**Last updated:** [May 8, 2024, 12:03am UTC](https://discourse.mozilla.org/t/post-mv3-versioning-for-cross-browser-extensions/129819 "2024-05-08T00:03:51Z")

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We’re submitting our MV3 extension for Chrome soon, and making a major version bump 5.1.4 -\> 6.0.0 for the change as it is effectively a different extension. 5.1.4 was the last version of our cross-browser code that was…

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## [MV3 and accessing file:/// resources (images)?](https://discourse.mozilla.org/t/mv3-and-accessing-file-resources-images/125395)

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**Author:** [@stig](https://discourse.mozilla.org/u/stig)\
**Replies:** 4\
**Last updated:** [December 23, 2023, 8:24am UTC](https://discourse.mozilla.org/t/mv3-and-accessing-file-resources-images/125395 "2023-12-23T08:24:18Z")

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With Mozilla and Google/Chromium (and Apples) latest agreement to allow a background-script to be defined as both a “event page” and a “service worker” in one and same manifest file, and browser picking only one way of r…

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## [Please improve the way host permissions are requested and granted in Manifest v3 (puzzle icon)](https://discourse.mozilla.org/t/please-improve-the-way-host-permissions-are-requested-and-granted-in-manifest-v3-puzzle-icon/122794)

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**Author:** [@dechobarca](https://discourse.mozilla.org/u/dechobarca)\
**Replies:** 1\
**Last updated:** [September 20, 2023, 8:19pm UTC](https://discourse.mozilla.org/t/please-improve-the-way-host-permissions-are-requested-and-granted-in-manifest-v3-puzzle-icon/122794 "2023-09-20T20:19:52Z")

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Yesterday I decided to give Manifest v3 extensions in Firefox a try to see how things work out. I wrote a very small extension that has a content script injected into example.com, and thus requiring host\_permissions for …

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## [How to ask \`browser.permissions.request\` from content\_script?](https://discourse.mozilla.org/t/how-to-ask-browser-permissions-request-from-content-script/120186)

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**Author:** [@Alex\_Kozack](https://discourse.mozilla.org/u/Alex_Kozack)\
**Replies:** 4\
**Last updated:** [June 12, 2023, 2:58pm UTC](https://discourse.mozilla.org/t/how-to-ask-browser-permissions-request-from-content-script/120186 "2023-06-12T14:58:50Z")

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I’m developing an extension that should synchronize data between two third-party websites (the user performs actions on one website, and a report on these actions is sent to the other website). I would like to insert th…

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## [onHeadersReceived does not work in mv3](https://discourse.mozilla.org/t/onheadersreceived-does-not-work-in-mv3/114257)

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**Author:** [@lakedai](https://discourse.mozilla.org/u/lakedai)\
**Replies:** 1\
**Last updated:** [May 12, 2023, 3:12pm UTC](https://discourse.mozilla.org/t/onheadersreceived-does-not-work-in-mv3/114257 "2023-05-12T15:12:53Z")

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hi, I have an extension that need bypass cors with credentials in mv3. And I try use webRequest.onHeadersReceived.addListener to change responseHeaders. After testing, I find the onHeadersReceived works in mv2 but not w…

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## [Overriding languages and user agent strings seen by web pages](https://discourse.mozilla.org/t/overriding-languages-and-user-agent-strings-seen-by-web-pages/113392)

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**Author:** [@metastable](https://discourse.mozilla.org/u/metastable)\
**Replies:** 4\
**Last updated:** [April 18, 2023, 7:57am UTC](https://discourse.mozilla.org/t/overriding-languages-and-user-agent-strings-seen-by-web-pages/113392 "2023-04-18T07:57:58Z")

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I am developing an extension that allows the user to set preferered languages and a user agent string for a container (contextual identity). In MV2, I used an approach where I define a dynamic content script string whic…

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## [How nonpersistent background pages work](https://discourse.mozilla.org/t/how-nonpersistent-background-pages-work/113359)

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**Author:** [@metastable](https://discourse.mozilla.org/u/metastable)\
**Replies:** 1\
**Last updated:** [April 15, 2023, 5:04pm UTC](https://discourse.mozilla.org/t/how-nonpersistent-background-pages-work/113359 "2023-04-15T17:04:35Z")

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Suppose I have the following code at the top level of a nonpersistent background script: browser.tabs.query({}).then((tabs) =\> console.log(tabs)); Does this piece of code run every time the background script resumes? I…

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## [MV3: Can .addListener() be inside a function?](https://discourse.mozilla.org/t/mv3-can-addlistener-be-inside-a-function/112834)

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**Author:** [@metastable](https://discourse.mozilla.org/u/metastable)\
**Replies:** 3\
**Last updated:** [April 2, 2023, 7:08am UTC](https://discourse.mozilla.org/t/mv3-can-addlistener-be-inside-a-function/112834 "2023-04-02T07:08:21Z")

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In MV3/nonpersistent background pages, we are told to avoid registering WE listeners asynchronously. Is it safe to register listeners inside a function/class, as long as it is called initially, not asynchronously?

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## [MV3 and Customizable Action Icon and Title](https://discourse.mozilla.org/t/mv3-and-customizable-action-icon-and-title/111716)

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**Author:** [@gchristnsn](https://discourse.mozilla.org/u/gchristnsn)\
**Replies:** 15\
**Last updated:** [March 8, 2023, 2:54pm UTC](https://discourse.mozilla.org/t/mv3-and-customizable-action-icon-and-title/111716 "2023-03-08T14:54:11Z")

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I need to make the icon and title of the action button customizable on MV3. The icon and title are stored in the local storage. A user can edit them any time in the add-on options. In the MV2 version of the add-on they a…

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## [Onboarding-page force-close before you have read it (with MV3 it becomes a critical issue I think)](https://discourse.mozilla.org/t/onboarding-page-force-close-before-you-have-read-it-with-mv3-it-becomes-a-critical-issue-i-think/111592)

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**Author:** [@stig](https://discourse.mozilla.org/u/stig)\
**Replies:** 3\
**Last updated:** [February 27, 2023, 9:17am UTC](https://discourse.mozilla.org/t/onboarding-page-force-close-before-you-have-read-it-with-mv3-it-becomes-a-critical-issue-i-think/111592 "2023-02-27T09:17:45Z")

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For a long time I have noticed a problem with mine and other extensions too. On a new install, an “onboarding page” might unwanted close when you select if an extension is to be allowed to run in Private Windows or not. …

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## [MV3 keep data in memory when popup closes](https://discourse.mozilla.org/t/mv3-keep-data-in-memory-when-popup-closes/110931)

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**Author:** [@muwave](https://discourse.mozilla.org/u/muwave)\
**Replies:** 3\
**Last updated:** [February 11, 2023, 11:19am UTC](https://discourse.mozilla.org/t/mv3-keep-data-in-memory-when-popup-closes/110931 "2023-02-11T11:19:20Z")

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Each time I open my MV3 extension the javascript runs from the beginning, it’s not persistent. If I set some variable and then close the extension, when I open it again the value stored in the variable is gone. I’m tryi…

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## [Manifest V3 support in Addons.Moziila.com](https://discourse.mozilla.org/t/manifest-v3-support-in-addons-moziila-com/105879)

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**Author:** [@blackforestboi](https://discourse.mozilla.org/u/blackforestboi)\
**Replies:** 7\
**Last updated:** [September 26, 2022, 5:05pm UTC](https://discourse.mozilla.org/t/manifest-v3-support-in-addons-moziila-com/105879 "2022-09-26T17:05:29Z")

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Hey folks, it seems as Manifest V3 support is starting to get ready. I was wondering if the Addons Store are already ManifestV3-only powered extensions, or will be accepting them by January 1st? Thanks!

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## [Error: Missing host permission for the tab](https://discourse.mozilla.org/t/error-missing-host-permission-for-the-tab/105769)

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**Author:** [@ferllings](https://discourse.mozilla.org/u/ferllings)\
**Replies:** 5\
**Last updated:** [September 23, 2022, 1:24pm UTC](https://discourse.mozilla.org/t/error-missing-host-permission-for-the-tab/105769 "2022-09-23T13:24:38Z")

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Hello, I’m doing some initial testing, for Manifest v3. When I’m trying to executeScript from background, I get “Error: Missing host permission for the tab” I have enabled scripting and activeTab, and everything I can…

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## [Using browser.scripting.executeScript in event listeners while upgrading to Manifest V3](https://discourse.mozilla.org/t/using-browser-scripting-executescript-in-event-listeners-while-upgrading-to-manifest-v3/102883)

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**Author:** [@adamouization](https://discourse.mozilla.org/u/adamouization)\
**Replies:** 8\
**Last updated:** [September 4, 2022, 12:31pm UTC](https://discourse.mozilla.org/t/using-browser-scripting-executescript-in-event-listeners-while-upgrading-to-manifest-v3/102883 "2022-09-04T12:31:17Z")

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Hi all, I have been working on upgrading my add-on from Manifest V2 to V3. However, I have been running in a few problems. Context: My add-on is a simple pop-up that modifies JS on the webpage that it is opened on via …

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## [Any news on declarativeNetRequest support in Manifest v3?](https://discourse.mozilla.org/t/any-news-on-declarativenetrequest-support-in-manifest-v3/105515)

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**Author:** [@snarfed](https://discourse.mozilla.org/u/snarfed)\
**Replies:** 2\
**Last updated:** [September 17, 2022, 4:41pm UTC](https://discourse.mozilla.org/t/any-news-on-declarativenetrequest-support-in-manifest-v3/105515 "2022-09-17T16:41:08Z")

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Hi all! I’m starting to work on migrating my manifest v2 extensions to v3, since they’re cross-browser and Chrome will stop running v2 extensions in Jan. Mozilla is evidently planning to support declarativeNetRequest as…

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## [Devtools\_page not working with Manifest V3](https://discourse.mozilla.org/t/devtools-page-not-working-with-manifest-v3/104134)

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**Author:** [@cmonday](https://discourse.mozilla.org/u/cmonday)\
**Replies:** 0\
**Last updated:** [August 25, 2022, 9:35pm UTC](https://discourse.mozilla.org/t/devtools-page-not-working-with-manifest-v3/104134 "2022-08-25T21:35:20Z")

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I’m preparing to upgrade React Developer Tooling add-on following this guide Manifest V3 migration guide | Firefox Extension Workshop I’ve got everything working with Manifest V3 on Chrome. But with Firefox, devtools ta…

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## [Does firefox has manifest v2 and v3 timeline?](https://discourse.mozilla.org/t/does-firefox-has-manifest-v2-and-v3-timeline/103494)

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**Author:** [@sudoaugustin](https://discourse.mozilla.org/u/sudoaugustin)\
**Replies:** 1\
**Last updated:** [August 21, 2022, 6:58pm UTC](https://discourse.mozilla.org/t/does-firefox-has-manifest-v2-and-v3-timeline/103494 "2022-08-21T18:58:48Z")

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If we visit this page, we can see the manifest v2 timeline for chrome. Do we have one like that for Firefox? I

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## [MV3 - Cannot get content script to run in Firefox! No errors and no loglines to be found!?](https://discourse.mozilla.org/t/mv3-cannot-get-content-script-to-run-in-firefox-no-errors-and-no-loglines-to-be-found/99589)

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**Author:** [@stig](https://discourse.mozilla.org/u/stig)\
**Replies:** 4\
**Last updated:** [July 14, 2022, 7:47am UTC](https://discourse.mozilla.org/t/mv3-cannot-get-content-script-to-run-in-firefox-no-errors-and-no-loglines-to-be-found/99589 "2022-07-14T07:47:19Z")

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Hi! As an early “proof-of-concept” (to sleep well at night), I tried to see how difficult it would be to migrate my Flickr Fixr webextension to MV3. Following the guide, I ended up only doing changes to the manifest.jso…

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## [Extensions using content scripts without any user action wont work anymore in MV3](https://discourse.mozilla.org/t/extensions-using-content-scripts-without-any-user-action-wont-work-anymore-in-mv3/98728)

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**Author:** [@robbendebiene](https://discourse.mozilla.org/u/robbendebiene)\
**Replies:** 6\
**Last updated:** [July 10, 2022, 7:13am UTC](https://discourse.mozilla.org/t/extensions-using-content-scripts-without-any-user-action-wont-work-anymore-in-mv3/98728 "2022-07-10T07:13:35Z")

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Lets assume we have an extension that simply sets the background color of each page to black. All it needs is the host permission \<all\_urls\> and a content script/style sheet that gets injected in every page. In MV2 the u…

[Next page](https://discourse.mozilla.org/tag/manifest-v3/126.md?match_all_tags=true&page=1&tags%5B%5D=manifest-v3)