HeaderInject

Inject custom HTTP headers into requests before interacting with web pages. Perfect for testing, development, and authentication.

Inject custom HTTP headers into web requests before interacting with pages. HeaderInject is built for testing, development, and authentication workflows that need precise header control. HeaderInject - Custom Headers Made Simple Add, edit, and manage HTTP request headers from a clean popup UI, then apply them instantly to matching sites - globally or per-header. Key Features: - One-click enable/disable toggle - Global URL pattern targeting (leave blank to apply everywhere) - Per-header domain scoping: assign one or more domains to a header (e.g. a different API key per environment) - headers without domains follow the global pattern - Add, edit, and delete multiple headers - Prevents duplicate header names - Save and apply changes in one action - Light and dark theme - Works across most request types (pages, XHR, fetch, media, etc.) - Local-only settings stored in the browser How It Works: 1. Open the extension popup 2. (Optional) Enter a global URL pattern like *://api.example.com/* 3. Add one or more headers (name + value) 4. (Optional) Scope a header to specific domains like api.example.com, staging.example.com 5. Click "Save & Apply" 6. Reload the page so the rules take effect Perfect For: - Testing APIs that require custom authentication headers or flags - Using different API keys for different domains or environments at the same time - Debugging staging environments with feature flags - Injecting tenant, locale, or environment headers - Quickly switching between header sets during development Privacy First: - No servers involved - Settings are stored locally - No data collection Tips: - If a header does not appear, the browser may restrict certain headers from being modified. - Reload the page after saving to ensure changes apply. - Leave a header's Domains field empty to let it follow the global URL pattern.