Header Override: An Open-Source Browser Extension to Modify HTTP Headers and Cookies
Header Override is an open-source browser extension that lets you modify HTTP request headers, response headers, request cookies, and response cookies directly in the browser.
It provides a simple way to test websites, APIs, staging environments, authentication flows, and feature flags without changing application code or backend configuration.
What can you do with Header Override?
Create local rules that apply only to selected URLs. You can add or replace HTTP headers, override request cookies, modify response cookies, and control cookie attributes such as Domain, Path, SameSite, Max-Age, and Secure.
Rules can be enabled, disabled, deleted, and documented with comments. URL filters help keep each change limited to the requests where it is needed.
Local profiles for different environments
Header Override supports up to five local profiles. You can use separate profiles for development, staging, testing, client accounts, or different API configurations.
Profiles can also be imported and exported as JSON files, making it easier to move configurations between browsers or computers.
Privacy-focused by design
All rules are stored locally in browser extension storage. Header Override does not require an account and does not use analytics, advertising, tracking, remote code, external servers, or third-party data sharing.
Browser support
Header Override is available for Chrome, Microsoft Edge, and Firefox.
Install Header Override
If you need a lightweight, open-source alternative to larger HTTP header modifier tools, Header Override focuses on the core workflow: create a rule, choose a URL, and test the result.
Learn more at headeroverride.com.
View the source code on GitHub.
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