OpenModHeader by Multivalence

Provides the features of the infamous ModHeader extension, but without any malware :D.

Header editing
- Set, append, or remove headers on both requests and responses
- Enable or disable any single header without deleting it
- Live count of active headers on the toolbar badge

Profiles
- Unlimited independent header sets, each with its own name and colour
- All enabled profiles apply at once, so you can layer an auth-token profile over a feature-flag profile
- Duplicate, rename, recolour, and delete from the profile menu

URL filtering
- URL contains — plain substring match
- URL matches regex — full regular expression
- Exclude domains — skip named domains and their subdomains
- Resource types — restrict to xmlhttprequest, main_frame, script, and so on
- Leave filters empty and the profile applies everywhere

Everything else
- Global on/off switch, plus Alt+Shift+H from anywhere
- Export and import profiles as JSON to share a setup or check it into a repo
- Open the popup in a full browser tab when you're editing a lot at once
- Follows your system light/dark theme
- Warns you before saving a rule the browser will reject

You may download directly from the source here if concerned about security.