# Extension source viewer

> View source code of Firefox add-ons and Chrome extensions (crx/nex/xpi) from addons.mozilla.org, the Chrome Webstore and elsewhere, with CRX Viewer (crxviewer).

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

## Overview

- **ID:** `crxviewer`
- **Platform:** Firefox
- **Type:** Firefox add-on
- **Status:** Available
- **Publisher:** Rob W
- **Category:** web-development,privacy-security
- **Daily users:** 1,555
- **Weekly downloads:** 40
- **Rating:** 4.87 / 5 (111 ratings)
- **Version:** 1.7.1
- **Last updated:** 2026-09-01
- **First published:** 2016-07-24
- **Size:** 243 KB
- **Data as of:** 2026-09-09
- **Store listing:** [Firefox Add-ons Store](https://addons.mozilla.org/firefox/addon/crxviewer/)
- **Website:** [https://github.com/Rob--W/crxviewer/issues](https://github.com/Rob--W/crxviewer/issues)

## Description

The Extension Source Viewer Chrome extension enables users to effortlessly view and download the source code of Firefox add-ons and Chrome extensions, including those for Opera, Edge, and Thunderbird. When detected, it adds a convenient button next to the address bar providing options to download the extension as a zip file or view its source directly.

The viewer tab offers advanced features such as syntax highlighting, automatic code beautification, regex-based file filtering and content search, image preview, and hash calculations for file integrity. Users can navigate search results easily, explore embedded zip files, and obtain permalinks within extension files. This versatile tool also facilitates downloading Chrome Web Store extensions for different platforms. Known as CRX Viewer or crxviewer, this extension enhances transparency and accessibility for developer and user communities.

## Rankings

- #2,538 — Overall
- #283 — Web Development
- #5 — source
- #10 — source code
- #15 — resource
- #15 — viewer

## Permissions and access

### Permissions

- `tabs`
- `storage`
- `contextMenus`
- `downloads`
- `alarms`
- `cookies`
- `webRequest`
- `webRequestBlocking`
- `*://*/*`

## 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 was recently updated in the past month. New updates 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).

## Review summary

Users praise Extension Source Viewer for enabling visibility into an add-on's code before installation, calling it handy and essential for security-conscious browsing. It generally works for downloaded addons, but several issues appear: the download as zip option sometimes fails; compatibility glitches (notably with Waterfox Classic) and occasional error messages when viewing code; and update problems that require reinstalling. Overall, it's valued as a safety tool despite these occasional drawbacks.

### Pros

- It lets you view the add-on's source code before install, boosting transparency.
- Handy and practical for checking what an add-on does.
- Works for downloaded add-ons and helps verify code before use.

### Cons

- The download as zip option can fail with a 'Failed' error.
- Compatibility issues with some browsers (notably Waterfox Classic) and related UI problems.
- Update/upgrade can require reinstalling the extension.

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