Firefox on Linux sourcemaps protocol error

Since about April 2023, I have been unable to edit css generated by SASS in Firefox’s DevTools Style Editor. If I click on a file listed by sourcemap, I receive the following error:

Error while fetching an original source: unsupported protocol for sourcemap request file:///home/.../sass/partials/_normalize.scss
Source URL: file:///home/.../sass/partials/_normalize.scss

... replaces actual path redacted for security.

The sourcemap file is syntactically correct. It has the /*# sourceMappingURL=<css_file_name> */ syntax. Working with webkit browsers such as Thorium, Chromium or Brave presents no error.

Through Google and DDG searches, all I have found on this topic is a similar unanswered post on

What is the extra step to accessing sourcemap files in Firefox DevTool Style Editor under Linux?

Looks like you’re hitting this error:

Would you know what protocol your sourcemap file is using?

1 Like

No, I don’t. I have been thinking file:// is the protocol and DevTools wants something else.

Is there anyone with insight to resolving this issue?

noticed it also fails for webpack.