User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:61.0) Gecko/20100101 Firefox/61.0 Build ID: 20180403220040 Steps to reproduce: I've got a css with sourcemaps like this: ``` ::-moz-selection { background-color: var(--color--action); color: #ffffff; } ::selection { background-color: var(--color--action); color: #ffffff; } /*# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbIi9Vc2Vycy9rdWQvUHJvamVjdHMvX2NvbnRleHRlL2xvaXMtd2ViYXBwL3NyYy9zdHlsZXMvc2VsZWN0aW9uLmNzcyJdLCJuYW1lcyI6W10sIm1hcHBpbmdzIjoiQUFBQTtFQUNFLHVDQUF1QztFQUN2QyxlQUFlO0NBQ2hCOztBQUVEO0VBQ0UsdUNBQXVDO0VBQ3ZDLGVBQWU7Q0FDaEIiLCJmaWxlIjoic2VsZWN0aW9uLmNzcyIsInNvdXJjZXNDb250ZW50IjpbIjo6LW1vei1zZWxlY3Rpb24ge1xuICBiYWNrZ3JvdW5kLWNvbG9yOiB2YXIoLS1jb2xvci0tYWN0aW9uKTtcbiAgY29sb3I6ICNmZmZmZmY7XG59XG5cbjo6c2VsZWN0aW9uIHtcbiAgYmFja2dyb3VuZC1jb2xvcjogdmFyKC0tY29sb3ItLWFjdGlvbik7XG4gIGNvbG9yOiAjZmZmZmZmO1xufVxuIl0sInNvdXJjZVJvb3QiOiIifQ== */ ``` Actual results: The result is a warning: Source map error: Error: sourceMapURL could not be parsed Expected results: I think it's because sourcemaps should be written like `//# sourceMappingURL=` as said there https://sourcemaps.io/ However, you can't do this kind of comment in CSS. So `/*# sourceMappingURL=` should be accepted too(?).

That form of comment definitely works. You can try a simple example here: https://tromey.github.io/source-map-examples/css/index.html Instead I think the problem comes from the URL itself. In particular I think the error is thrown here: https://github.com/mozilla/source-map/blob/master/lib/util.js#L529 source-map uses a phony URL parser that does: var urlRegexp = /^(?:([\w+\-.]+):)?\/\/(?:(\w+:\w+)@)?([\w.-]*)(?::(\d+))?(.*)$/; ... var match = aUrl.match(urlRegexp); Sure enough, this doesn't work for the data: URL here. I think the best fix would be to change source-map to use URL directly. This should be possible now that it requires newer versions of node.

Upstream bug is here: https://github.com/mozilla/source-map/issues/275 Though once that is fixed it will need a new release, then a new devtools-core release, then landing in M-C.

:tom

Hi! This issue is affecting our own webdevs, as well as the wider community. Is there a rough timeframe for when someone might be able to take a look at this? https://github.com/mozilla/source-map/issues/275

Thanks Ed, https://github.com/mozilla/source-map/issues/275 is in our OKRs for Q4. Looks like we also got community on it now as well.

That's great - thank you :-)