Header Handler

A simple, open-source header editor. No accounts, no tracking, no servers, no mess. Header Handler adds, overwrites, and removes HTTP request headers — that's it. It's fully open source, makes no network requests of its own, phones home to nothing, and runs no remotely hosted code. Nothing you configure ever leaves your machine. Install it, set a rule, done. You define named profiles, each with a URL matcher and a list of header rules (Set or Remove). Multiple profiles can be active at once; the applied rule set is the union of everything enabled. Shareable in one string. Every profile — or your whole setup — exports to a single copy-paste string. Send it to a teammate or paste it into another browser and they have the exact same rules in seconds. No sign-up, no sync account, no config files to pass around. Built for local development and debugging. Inject headers into requests without a proxy, strip or override Origin / Referer / Cookie per site, and scope rules with six matcher modes (Contains, Exact, Starts with, Ends with, Domain, Custom regex) — with an optional per-rule override matcher for one-off exceptions. See what actually matched. A side panel live log lists requests touched by your active rules, with the observed headers for that request — added or changed headers highlighted against the rest. Session-only; cleared when the browser closes or on demand. Where your data lives (all on-device). • Profiles and rules are stored in Chrome's own synced storage (chrome.storage.sync) — the same mechanism as bookmarks. • The live log lives only in memory for the browser session (chrome.storage.session) and is never written to disk. • Everything ships in the extension package — no remotely hosted code. Scope note (by design): the live log uses read-only webRequest observation to reconstruct which rules applied — Manifest V3 doesn't expose per-request rule-match ground truth to a published extension. The actual header rewriting is done entirely by declarativeNetRequest, not by webRequest. Open source — https://github.com/curtyo18/header-handler