Our Drupal 9 site is full of "page not found" warnings in the Drupal logs. All entries end in *.js.map (all map files). I cannot figure out where the warnings are coming from (what system is trying to find non-existent map files?) or how to resolve.

See screenshot for examples of not-found files.


1 Answer 1


It means that someone browsed the site with developer tools enabled, which tried to load debugging files that do not exist.

.map files, known as "sourcemap" files, are used by web browser developer tools for debugging CSS and JavaScript by allowing minified and aggregated CSS and JavaScript to appear in their original source code forms.

.map files are not necessary for the normal operation of a web site. If .map files are missing, it is because a preprocessor did not create them, or in some cases, a vendor did not provide them.

There is an open issue in Drupal core to create these.

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