Ghillie Up

Modify HTTP request headers per profile, per site.

Ghillie Up is an open-source extension for modifying HTTP request headers — organized into profiles, scoped to the sites you choose. Create a profile, add the headers you want to inject, and list the sites where they should apply. Need different headers for different environments, APIs, or test setups? Run multiple profiles at once — profile order decides priority when they conflict, and you can reorder them with a simple drag.