# User-Agent Header Manager

> Customize your browser's User-Agent and other HTTP headers with ease. This powerful extension lets you modify how websites see your browser, perfect for testing, development, and privacy customization.

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

## Overview

- **ID:** `user-agent-header-manager`
- **Platform:** Firefox
- **Type:** Firefox add-on
- **Status:** Available
- **Publisher:** Viacheslav Zhabonos
- **Category:** web-development,privacy-security
- **Daily users:** 1
- **Version:** 1.0.1
- **Last updated:** 2026-02-23
- **First published:** 2026-02-17
- **Size:** 37 KB
- **Data as of:** 2026-09-05
- **Store listing:** [Firefox Add-ons Store](https://addons.mozilla.org/firefox/addon/user-agent-header-manager/)

## Description

User-Agent Header Manager

Customize your browser's User-Agent and other HTTP headers with ease. This powerful extension lets you modify how websites see your browser, perfect for testing, development, and privacy customization.

Features

<strong>Global &amp; Per-Site Control</strong>
- Set default headers that apply to all websites
- Override headers for specific sites individually
- Hierarchical configuration: global defaults with site-specific overrides

<strong>User-Agent Presets</strong>
- Quick selection of popular browser User-Agents
- Chrome, Firefox, Safari, Edge on Windows, macOS, and Linux
- Mobile browsers: iOS Safari, Android Chrome
- Search engine bots: Googlebot, Bingbot

<strong>Custom Headers</strong>
- Modify any HTTP header beyond User-Agent
- Accept-Language, Referer, Accept-Encoding, and more
- Add custom headers for specialized testing

<strong>Flexible Targeting</strong>
- Blacklist mode: Apply to all sites except ones you exclude
- Whitelist mode: Only apply to specific sites you choose
- Wildcard support: Use *.example.com patterns

<strong>Persistence</strong>
- All settings saved automatically
- Survives browser restarts
- Import/Export settings for backup or sharing

Use Cases
<ul><li><strong>Web Development</strong>: Test how your site responds to different browsers and devices</li><li><strong>Privacy</strong>: Blend in with common User-Agents</li><li><strong>Access Control</strong>: Access mobile or desktop versions of websites</li><li><strong>SEO Testing</strong>: View your site as search engine crawlers</li><li><strong>API Testing</strong>: Debug how servers respond to different headers</li><li><strong>Compatibility Testing</strong>: Ensure your site works across browsers</li></ul>
How It Works

The extension intercepts HTTP requests and modifies headers before they leave your browser. Headers are applied in order of specificity: global headers serve as defaults, and site-specific configurations override them for particular domains.

Permissions

This extension requires access to all URLs to modify HTTP headers for any website you visit. All settings are stored locally in your browser - no data is sent to external servers.

Privacy

Your privacy is important. This extension:
- Stores all data locally in your browser
- Does not collect any personal information
- Does not send data to external servers
- Works completely offline after installation

## Rankings

- #122,300 — Overall
- #120 — agent

## Permissions and access

### Permissions

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

## Safety

- **Risk impact:** High risk impact
- **Risk likelihood:** Moderate 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).

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