Header Tool

Easily modify HTTP headers on every request with a simple text editor, JS expressions, and regex URL matching.

Full Description:

Header Tool lets you modify HTTP request headers using a simple text editor interface. Write headers directly, use JavaScript expressions for dynamic values, and target specific URLs with regular expressions.

Features:

• Simple text-based editor — no complex UI, just type your headers • JavaScript expressions in ${...} blocks: base64 encoding, crypto hashes, dynamic dates, and more • Regular expression URL matching with @ syntax — apply different headers to different sites • Continuous JS mode — re-evaluates expressions on every HTTP request • Copy headers to clipboard in wget or curl format • Import/Export header configurations from/to text files • Persistent — your headers and settings survive browser restarts • Sidebar panel (F4) and toolbar popup for quick access • Does not interfere with Firefox Sync or internal browser services

Usage example:

Basic header

X-Custom-Header: my-value

Base64 authentication

Authorization: Basic ${b64("username:password")}

Dynamic values

X-Timestamp: ${new Date().toISOString()}

Apply only to specific URLs

@api.example.com X-API-Key: secret123

Crypto

X-Hash: ${sha256("message")} Supported JS functions: b64(), md5(), sha1(), sha256(), crypto(), hostname(), pathname(), search(), href()

Source code: https://github.com/loreii/HeaderTool