How to configure Firefox color management
Firefox is a fully color managed browser, but unfortunately that capability is enabled by default only for images tagged with ICC color profiles.
Firefox 77 color management bug
The latest version of Firefox introduced a bug that disabled color management for untagged images in JPG, PNG and WebP formats. Effectively, now all images with no color profile information are rendered on the full display gamut, leading to oversaturated colors, despite the color management mode setting. This is the change that introduced this error and here is the relevant bug tracker entry.
Firefox 78 fixes that issue and properly consider untagged images as sRGB. Unfortunately, files tagged with ICC v4 profiles now show some color distortion and Firefox doesn't pass our color management test completely. I'll probably do some regression testing on the next few days and file a bug with Mozilla about this issue. At least v4 profiles are not that popular and there are few reasons for using them on the web, anyway.
How to enable color management in Firefox and fix oversaturated colors
By default, Firefox only enables color management for images tagged with ICC color profiles.
All other page elements and untagged images are rendered on the full monitor color gamut, leading to inaccurate and over-saturated colors, specially on wide gamut displays. Read more about it on our browser color management guide.
In order to enable and properly configure Firefox color management for all images and page elements, according to the W3C specification, follow the steps below.
Enable it on the Firefox advanced configuration
Type in about:config on your Firefox address bar.
Use the filter field to search for color_management.
Update the following fields:
Set to 1 to enable color management for all rendered graphics.
The default value of 2 enables color management only for tagged images, so all page elements and untagged images are rendered in the monitor full color gamut, leading to oversaturated colors.
Set to true to enable ICC v4 profile support.
There's no need to specify the monitor ICC profile manually as it's read automatically from the operating system.
You can check how your browser's color management is behaving by accessing our browser color management test.
If you're interested in color management, make sure to check my recent Datacolor SpyderX Pro review. It's an excellent monitor calibration tool for the price.