User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:45.0) Gecko/20100101 Firefox/45.0 Build ID: 20160325004906 Steps to reproduce: In HTML I link to an SVG image: <img src="image.svgz" alt="Image" style="width: 60%; height: auto;"/> Actual results: The image is not shown when I open the webpage directly from the local filesystem without a webserver. When I upload the exact same webpage and the image to a webserver where the HTTP headers for SVGZ are configured, it does work. Expected results: Local SVG (uncompressed) works, SVGZ should work as well. The file extension .svgz indicates that it is a compressed SVG file, so Firefox should have enough information to guess that it can treat it as compressed SVG, despite the HTTP headers missing locally.

Could you attach a testcase to the bug report, so we could test locally ourself.

This test-case contains an HTML file that links to two SVG files. One is plain SVG, the other is compressed SVGZ. Both files work when placed on-line and loaded from a webserver, but the compressed SVGZ fails when loaded from local filesystem.

In this screenshot you can see that the HTML file is loaded locally, and the compressed SVG is not loaded. No error is shown in console.