Consider including flutter.js.map in the build output folder #145111

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1. danagbemava-nc

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   toolAffects the "flutter" command-line tool. See also t: labels.Affects the "flutter" command-line tool. See also t: labels.

   platform-webWeb applications specificallyWeb applications specifically

   c: proposalA detailed proposal for a change to FlutterA detailed proposal for a change to Flutter

   a: buildBuilding flutter applications with the toolBuilding flutter applications with the tool

   team-webOwned by Web platform teamOwned by Web platform team

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   on Mar 14, 2024
2. yjbanov

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   P2Important issues not at the top of the work listImportant issues not at the top of the work list

   triaged-webTriaged by Web platform teamTriaged by Web platform team

   on Mar 21, 2024
3. henryqum commented on Jul 15, 2024

   

   henryqum

   on Jul 15, 2024

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   Hi, my flutter web app break on safari because it can't load flutter.js.map, i get Failed to load resource: the server responded with a status of 404 (), the browser manage to load all other files

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4. BenBroide commented on Jul 18, 2024

   

   BenBroide

   on Jul 18, 2024

   Last edited by BenBroide

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   Same issue. Web app breaks on mobile browsers, even when adding flags flutter build web --release --source-maps the file flutter.js.map is not generated
5. BenBroide commented on Jul 18, 2024

   

   BenBroide

   on Jul 18, 2024

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   Hi, my flutter web app break on safari because it can't load flutter.js.map, i get Failed to load resource: the server responded with a status of 404 (), the browser manage to load all other files

   Could be something else is breaking your web app but the only error is the .map file error
   In my case something else was breaking the app.
   You can try by setting a placeholder map file and see which errors you have after
6. henryqum commented on Jul 18, 2024

   

   henryqum

   on Jul 18, 2024

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   In my case something else was breaking the app.

   could be, what broke your app?
7. BenBroide commented on Jul 18, 2024

   

   BenBroide

   on Jul 18, 2024

   Last edited by BenBroide

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   In my case something else was breaking the app.

   could be, what broke your app?

   I moved some variables to a .env file and did not adjust git actions to set them while deploying.
   Try to set this in your app as placeholder and see which error show up in console once the .map file error will be gone. The error will probably not show the exact code since it's not a real .map file

   flutter.js.map

   {
       "version": 3,
       "file": "flutter.js",
       "sources": [],
       "names": [],
       "mappings": ""
     }
   
8. henryqum commented on Jul 18, 2024

   

   henryqum

   on Jul 18, 2024

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   @BenBroide Sure, I'll try that. Thanks for your suggestion.
9. olof-dev commented on Nov 14, 2024

   

   olof-dev

   on Nov 14, 2024

   Last edited by olof-dev

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   It seems like {{flutter_js}} in index.html includes a line

   //# sourceMappingURL=flutter.js.map
   

   at the end. Since that file isn't provided automatically, it'll most likely show up as a console warning in many browsers.

   This happens regardless of whether --no-source-maps is specified in flutter build web. If the resolution of this issue is to include the source map automatically, should it be regardless of --[no-]source-maps?
10. tbecker commented on Feb 5, 2025

    

    tbecker

    on Feb 5, 2025

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    I use flutter 3.27 and have the same issue, when using the developer tools in Chrome, Safari, Firefox on Mac Sequioa 15.2

    I run build with --source-maps

    I receive the following error message from the python http server
    ::1 - - [05/Feb/2025 10:36:05] code 404, message File not found
    ::1 - - [05/Feb/2025 10:36:05] "GET /flutter.js.map HTTP/1.1" 404 -

    While main.dart.js.map is available, flutter.js.map is missing in the build/web directory. Again, the error is only relevant when using the developer Javascript tools, not in normal mode.
11. PascalHaupt commented on Feb 26, 2025

    

    PascalHaupt

    on Feb 26, 2025

    Last edited by PascalHaupt

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    Is there any update on this? We need the mappings (flutter.js.map) for sentry. Even when configuring sentry to upload the sources also, the stack trace still isn't useful.

    It seems that the mapping file flutter.js.map won't be created at all. I can't find it anywhere in my entire project folder. For building I use the command flutter build web --source-maps. Currently, we are using flutter 3.27.0 but double checked the current version too (as of time of writing this is 3.29.0). We even tested it with an empty, newly created flutter project and got the same result.

    Since we include flutter.js in the output build directory, it might be worthwhile to also include flutter.js.map by default.

    Does this mean the mapping file can be grabbed from somewhere? If so, where can one find it? A viable workarounf for now could be to copy this file manually into the build/web directory.

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12. Goshagosha commented on Mar 11, 2025

    

    Goshagosha

    on Mar 11, 2025

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    Does this mean the mapping file can be grabbed from somewhere? If so, where can one find it? A viable workarounf for now could be to copy this file manually into the build/web directory.

    Facing same issue as you, with the need to upload maps to sentry, I found that maps can be found at $FLUTTER_HOME/bin/cache/flutter_web_sdk/flutter_js/flutter.js.map

    Copying them manually for now, but it really would make sense, if --source-maps flag did this automatically

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13. DarioCorno commented on Jan 15, 2026

    

    DarioCorno

    on Jan 15, 2026

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    Any updat on this one? Latest flutter release still doesn't properly generate flutter.js.map and breaks mobile Safari

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14. auto-submit

    closed this as completedin #192257on Sep 29, 2026
15. pull

    added a commit that references this issue on Sep 29, 2026

    [flutter_tools] Include flutter.js.map in web builds (flutter#192257)

    ...

    This issue will close once commit 1e847f2 is merged into the 'master' branch.

    1e847f2