HeaderLock – Modify HTTP Request & Response Headers

Modify HTTP request & response headers per URL. Imports ModHeader JSON. No tracking, browsing data never leaves Chrome.

Add, change or remove HTTP headers on the sites you choose. HeaderLock is a header editor for developers and testers, built so you can trust what it does with your traffic: nothing. WHAT IT DOES • Request and response headers: set, append or remove any header (Authorization, Cookie, User-Agent, CORS, CSP, caching…). • URL filters: wildcards (||api.example.com, localhost:3000/*) or regex. "Only on" and "Not on" rules. • Profiles: one per environment (staging, QA, local). Switch with [ and ], pause everything with P. • This tab only: keep a profile to a single tab while you test. • Variables: write {{token}} once, use it in every profile. • The badge shows how many headers are active right now. COMING FROM MODHEADER Paste or drop your ModHeader export (any version, including old v1 files). HeaderLock maps headers, append and remove modes, URL and exclude filters, resource types and request methods, and tells you exactly what it couldn't carry over. Profiles that used filters it can't apply safely (time, tab or window filters) are imported switched off rather than widened to every page. Simple ModHeader regex filters are converted to wildcards with the same meaning, so they keep working on the free plan. You can export back to ModHeader's format at any time. No lock-in. PRIVACY YOU CAN CHECK • Free makes no network requests at all. • Pro checks its licence once a day with our licence server. That is the only request the extension ever makes. • Your headers stay in this browser. Chrome applies them through declarativeNetRequest, so HeaderLock never reads your requests or pages. • No analytics, no remote code, no host access at install. Access is requested per site, when you need it. • To verify, open chrome://extensions, turn on Developer mode, and open HeaderLock's service worker. Its Network tab shows every request. FREE AND PRO Free: one profile with five headers, request headers, wildcard filters. Free forever. Pro: unlimited profiles and headers, response headers, regex filters, variables. $29 once for lifetime access, or $3.99 a month. Launch price: $9 lifetime until November 30, 2026. KEYBOARD · N new request header · Shift+N new response header · F new filter · P pause · [ ] switch profile · Enter next field · Cmd/Ctrl+Backspace delete row · Alt+Shift+H open · Alt+Shift+P pause from anywhere. HeaderLock is not affiliated with ModHeader or its developers. Support: tailsgate.com/headerlock/support Privacy policy: tailsgate.com/headerlock/privacy