Several Firefox settings work together to determine how web content and browser chrome are rendered. They can be hard to keep track of! Use the flowcharts below for quick reference.
Settings that control color usage in browser chrome¶
Windows: High Contrast Mode in OS accessibility settings
macOS: Increase Contrast in OS accessibility settings
Linux: High Contrast Theme in OS accessibility settings
FF Theme (AKA FF Colorway) Note: OS HCM settings will only trigger HCM color usage in chrome if a user’s FF theme is set to “system auto”. If they have a pre-selected colorway or other FF theme (including explicit “Dark” or “Light”) they will not see color changes upon enabling OS HCM.
Settings that control color usage in content¶
Colors Dialog (about:preferences > Manage Colors)
Dropdown with options: Always, Only with High Contrast Themes, and Never
Use System Colors checkbox
Text, Background, Visited and Unvisited Link color inputs
Extensions like Dark Reader, or changes to user.css, may override author specified colors independent of HCM.