# Header Tool

> A simple HTTP header modifier extension with JS expressions, regex URL matching, and clipboard export.

Canonical page: [https://chrome-stats.com/d/header-tool](https://chrome-stats.com/d/header-tool)

## Overview

- **ID:** `header-tool`
- **Platform:** Firefox
- **Type:** Firefox add-on
- **Status:** Available
- **Publisher:** loreii
- **Category:** web-development
- **Daily users:** 22
- **Weekly downloads:** 1
- **Version:** 1.0.0
- **Last updated:** 2026-06-15
- **First published:** 2026-06-12
- **Size:** 36 KB
- **Data as of:** 2026-09-09
- **Store listing:** [Firefox Add-ons Store](https://addons.mozilla.org/firefox/addon/header-tool/)
- **Website:** [https://github.com/loreii/HeaderTool](https://github.com/loreii/HeaderTool)

## Description

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: <a href="https://prod.outgoing.prod.webservices.mozgcp.net/v1/45b3bc39733ff91611134fbba643a7a07310f7dab04bdd71fc5a51314fd91587/https%3A//github.com/loreii/HeaderTool" rel="nofollow">https://github.com/loreii/HeaderTool</a>

## Rankings

- #23,583 — Overall
- #28 — header
- #110 — tool
- #124 — modify

## Permissions and access

### Permissions

- `webRequest`
- `webRequestBlocking`
- `storage`
- `tabs`
- `clipboardWrite`
- `downloads`
- `<all_urls>`

## Safety

- **Risk impact:** High risk impact
- **Risk likelihood:** High risk likelihood

### Analysis details

- Grants access to browser tabs, which can be used to track user browsing habits and history, presenting a privacy concern.
- This extension has low user count. Unpopular extensions may not be stable or safe.

> Some risk analysis details are omitted from this free response. [Upgrade to view the full analysis](https://chrome-stats.com/pricing).

## Similar extensions and apps

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- [Overhead — HTTP Header Editor](https://chrome-stats.com/d/overhead-http-header-editor) — 1 users, 5.00 / 5

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Source: [Chrome-Stats](https://chrome-stats.com/d/header-tool)