---
title: Assessing your Safari web extension’s browser compatibility
framework: safariservices
role: article
role_heading: Article
path: safariservices/assessing-your-safari-web-extension-s-browser-compatibility
---

# Assessing your Safari web extension’s browser compatibility

Review your Safari web extension implementation plan, manifest keys, and JavaScript API usage for compatibility with other browsers.

## Overview

Overview Safari web extensions provide a number of features for compatibility with other browsers and a good developer experience, while ensuring the safety and privacy that users expect. Review your extension implementation or planned approach, manifest.json key usage, and selected JavaScript APIs for incompatibilities, and get suggestions and workarounds for potential issues. Review your implementation plan Consider these factors when reviewing your implementation plan for your Safari web extension, and make adjustments as needed: Safari web extensions support both the chrome.* and browser.* namespaces. Use them as appropriate for your extension and your plan for browser compatibility. Safari web extensions support both the callback and Promise approaches for asynchronous APIs. Use the most suitable approach for your code quality and browser compatibility. Safari ignores file URL schemes in manifest permissions. If you use them, adjust your implementation. Review your manifest Generally, Safari web extensions ignore any unsupported manifest keys, but you may need to develop workarounds or alternative approaches for any incompatibilities. Check for these keys in your manifest and take action where needed: Safari 15.4 and later supports manifest versions 2 and 3. To evaluate compatibility for manifest keys in your extension, see Mozilla’s compatibility table at  Browser compatibility for manifest.json. Review your web extension API usage Generally, Safari ignores any unsupported JavaScript APIs, but you may need to develop workarounds or alternative approaches for any incompatibilities. Check for these APIs in your Safari web extension and take action where needed: BlockingResponse not supported. Blocking requests not supported. opt_extraInfoSpec not supported for any of the events. To evaluate compatibility for JavaScript extension APIs in your Safari web extension, see Mozilla’s compatibility table at Browser support for JavaScript APIs.

## See Also

### Extension improvements

- [Optimizing your web extension for Safari](safariservices/optimizing-your-web-extension-for-safari.md)
- [Adopting New Safari Web Extension APIs](safariservices/adopting-new-safari-web-extension-apis.md)
- [Syncing Safari web extensions across devices and platforms](safariservices/syncing-safari-web-extensions-across-devices-and-platforms.md)
- [Troubleshooting your Safari web extension](safariservices/troubleshooting-your-safari-web-extension.md)