# HeaderMod

> Inject, update, edit, modify, override HTTP headers

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

## Overview

- **ID:** `headermod`
- **Platform:** Firefox
- **Type:** Firefox add-on
- **Status:** Available
- **Publisher:** UtilsFactory
- **Category:** web-development
- **Daily users:** 303
- **Weekly downloads:** 15
- **Version:** 25.4
- **Last updated:** 2025-08-09
- **First published:** 2025-06-27
- **Size:** 21 KB
- **Data as of:** 2026-09-05
- **Store listing:** [Firefox Add-ons Store](https://addons.mozilla.org/firefox/addon/headermod/)
- **Website:** [https://github.com/UtilsFactory/HeaderMod](https://github.com/UtilsFactory/HeaderMod)

## Description

<strong>HeaderMod - Inject, update, edit, modify, override HTTP headers</strong>

A lightweight and open source browser extension that lets you intercept outgoing HTTP requests and inject, update, edit, modify, or override headers on a per-URL basis.

<strong>Key Features</strong>
<ul><li>Define multiple header-modification rules</li><li>Wildcard-based URL matching (e.g., <em>.example.com/</em>)</li><li>Add or replace any request header (name + value)</li><li>Enable or disable rules individually</li><li>Persist rules in local storage for seamless browser restarts</li><li>Dynamic toolbar icon indicates active rules</li></ul>
<strong>Usage</strong>
<ol><li>Click the HeaderMod toolbar icon to open the popup.</li><li>Click Add Rule to create a new entry, then fill in:<ul><li>Header-Name and Header-Value</li><li>Optional URL Pattern (supports * wildcards)</li><li>Optional Notes for your reference</li><li>Enabled checkbox to toggle the rule</li></ul></li><li>Modify or delete rules as needed.</li></ol>
<strong>What happens next</strong>
<ul><li>Browse your sites as usual</li><li>Each enabled rule is tested against the request URL</li><li>Matching requests have their headers updated or appended before they leave the browser</li></ul>
<strong>Privacy</strong>
<ul><li>HeaderMod does not collect, transmit, or share any personal data. All settings remain in your browser’s local storage and are never sent to any external server.</li></ul>
Whether you need to spoof headers for testing or inject custom metadata into requests, HeaderMod puts you in control.

## Rankings

- #6,675 — Overall
- #4 — modheader
- #16 — header
- #29 — override
- #47 — inject
- #51 — modify

## Permissions and access

### Permissions

- `webRequest`
- `webRequestBlocking`
- `<all_urls>`
- `storage`

## Safety

- **Risk impact:** Moderate risk impact
- **Risk likelihood:** Moderate risk likelihood

### Analysis details

- Allows access to all websites, posing a significant security risk as it can monitor and modify data from any visited site.
- 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

- [ModHeader](https://chrome-stats.com/d/modheader-firefox) — 19,864 users, 3.37 / 5
- [Header Override](https://chrome-stats.com/d/header-override) — 39 users
- [Header Ext](https://chrome-stats.com/d/header-ext) — 3 users
- [HTTP Header Plugin](https://chrome-stats.com/d/http-header-plugin) — 6 users
- [Modify Header Value](https://chrome-stats.com/d/modify-header-value) — 9,880 users, 3.62 / 5
- [ModHeader By GreatJIN](https://chrome-stats.com/d/modheader-by-greatjin) — 27 users
- [Configurable Header Manager](https://chrome-stats.com/d/configurable-header-manager) — 2 users
- [xHeader - Modify HTTP headers](https://chrome-stats.com/d/xheader) — 2 users
- [Header Override](https://chrome-stats.com/d/headeroverride) — 7 users
- [Header Tool](https://chrome-stats.com/d/header-tool) — 23 users
- [Header request Injector](https://chrome-stats.com/d/header-request-injector) — 3 users
- [simple-modify-headers](https://chrome-stats.com/d/simple-modify-header) — 6,024 users, 4.62 / 5

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