Header Override od headeroverride.com

Header Override lets you create local rules that modify HTTP request headers for URL patterns you choose.

Use it to add or override request headers while testing APIs, debugging websites, working with staging environments, or reproducing header-dependent behavior.

Rules include a header name, value, URL filter, enabled state, and optional comment. Rules are stored locally in your browser and applied through Firefox's declarativeNetRequest API.

Header Override does not use analytics, tracking, advertising, remote code, or external servers. Your rules and browsing activity are not sent to the developer or any third party.