Free online CRX to XPI converter

Source format: crx

CRX is the package format used by Google Chrome and other Chromium-based browsers for extensions. It contains the extension files plus Chrome-specific metadata and a digital signature. CRX files are usually distributed through the Chrome Web Store or installed manually in Chromium-based browsers. They are not a general-purpose archive format, so they are meant to be loaded by an extension system rather than opened like a normal document.

Target format: xpi

XPI is the extension package format used by Mozilla Firefox and other Mozilla-based applications. It is essentially a ZIP-based package with extension metadata and signing requirements for modern Firefox versions. XPI files are used to install browser add-ons, themes, and related extension packages.

How to convert crx to xpi

There is no true one-click conversion from CRX to XPI because Chrome and Firefox extensions often use different APIs, permissions, and manifest requirements. In many cases, you must extract the CRX contents, adapt the extension code for Firefox, then package it as an XPI.

Best desktop tools: Firefox Developer Edition for testing, 7-Zip or WinRAR for extraction, and web-ext from Mozilla for packaging and testing.

1. Obtain the .crx file.
2. Extract its contents with 7-Zip, WinRAR, or a CRX extraction utility. If the archive tool cannot open it directly, try renaming the file to .zip only as a quick test; many CRX files will still require a dedicated extractor.
3. Inspect the extension files, especially manifest.json, background scripts, permissions, and any Chrome-specific APIs.
4. Modify the extension for Firefox compatibility if needed. Common changes include replacing Chrome-only APIs with WebExtensions-compatible equivalents and adjusting manifest settings.
5. Test the unpacked extension in Firefox by opening about:debugging and using This Firefox → Load Temporary Add-on to select manifest.json.
6. When the extension works correctly, package it with Mozilla’s web-ext tool. For example, run web-ext build in the extension folder to create a package archive.
7. If you need a distributable XPI, use Mozilla’s signing workflow. For example, web-ext sign can submit the add-on for signing through Mozilla’s services.

Useful commands: web-ext run for testing, web-ext build for packaging, and web-ext sign for signing through Mozilla’s add-on services.

Online converters: There are few reputable true CRX-to-XPI converters because the formats are not directly interchangeable. Some online tools can extract CRX contents, but they usually do not produce a fully functional Firefox add-on. For safety and reliability, desktop tools and manual adaptation are strongly preferred.

Notes on compatibility and limitations

CRX to XPI is often a port, not a pure conversion. Many Chrome extensions rely on APIs or behaviors that Firefox does not support exactly the same way. If the extension uses only standard WebExtensions APIs, conversion may be straightforward. If it depends on Chrome-specific features, native messaging, or Manifest V2/V3 differences, you may need code changes.

Modern Firefox requires signed add-ons for normal installation, so an XPI created from a CRX may still need Mozilla signing before it can be installed outside developer mode. Also, some extensions cannot be converted at all without substantial rewriting.

If your goal is simply to use a Chrome extension in Firefox, check whether the extension already has a Firefox version or whether Firefox’s built-in extension compatibility is sufficient. For best results, use the extension’s source code and rebuild it specifically for Firefox.

Best online option: If you only need to inspect or unpack a CRX, use a reputable file-extraction service or local extraction tool rather than a full conversion website. For actual Firefox use, Mozilla’s Extension Workshop is the best place to learn how to port, test, and publish the add-on: Porting a Google Chrome extension.