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A browser and nodejs javascript library for being able to override import maps. This works with native browser import maps, SystemJS import maps, es-module-shims import maps, and more.


import map overrides 3

Import maps are a way of controlling which url to download javascript modules from. The import-map-overrides library allows you to dynamically change the url for javascript modules by storing overrides in local storage. This allows developers to override individual modules to point to their localhost during development of a module, without having to boot up a local environment with all the other modules and a backend server.

You should not use import-map-overrides as the only import map on your page, since you cannot count on everyone's local storage having valid values for all of your modules. Instead, import-map-overrides should be viewed as a developer experience enhancement and dev tool -- developers can develop and debug on deployed environments instead of having to boot up a local environment.

Here are some tutorial videos that explain this in more depth:


The UI for import-map-overrides works in evergreen browsers (web components support required). The javascript API works in IE11+.




Make sure you commit a changeset with pnpm changeset before you open a PR. This will allow to automatically bump the version and maintain the CHANGELOG once released.