HeaderDeck - HTTP Header Manager

Modify HTTP request and response headers with profile and wildcard-domain rules.

HeaderDeck is an HTTP header management tool for web development, testing, and API debugging. It lets you create site-specific profiles that modify request or response headers, with precise controls for domains, URLs, request methods, and resource types. Use HeaderDeck to add authentication headers, switch between environments, test caching and CORS behavior, or inspect selected response headers. Request IDs, cache status, and other values can be displayed as text or rendered as convenient links. HeaderDeck also supports quick profile toggles, a global on/off switch, temporary tab-scoped rules, and YAML import, export, and change review. Instead of repeatedly editing application code or configuring developer tools, HeaderDeck keeps reusable header rules organized in one place and clearly shows where each profile applies. Configuration and Inspect results are processed locally in the browser, without remote accounts, analytics, or a backend service. If you regularly work with frontend integration, API testing, environment switching, cache troubleshooting, or request tracing, HeaderDeck makes these workflows faster, more controlled, and easier to reuse.