Software⏱️ 3 min read📅 2026-06-15

How to Fix: "@font-face encountered unknown error." from IE11 on Windows 10

IE11 compatibility issue with custom fonts on Windows 10

Quick Answer: Try using a different font or font format, or consider using a polyfill to support IE11.

📋 Table of Contents

  1. ⚠️ Common Causes
  2. ✅ Best Solutions to Fix It
  3. 💡 Conclusion

The error '@font-face encountered unknown error.' in Internet Explorer 11 (IE 11) on Windows 10 is a common issue that affects web developers who use custom fonts in their websites. This error prevents IE 11 from rendering the font correctly, resulting in a broken user interface and a poor browsing experience.

This problem can be frustrating for web development shops like yours, as you need to test sites in IE to ensure compatibility. However, with the right troubleshooting steps, you should be able to resolve this issue and get your custom fonts working in IE 11.

⚠️ Common Causes

  • The primary reason for this error is that IE 11 does not support the 'font-family' syntax used in modern web fonts. This syntax was introduced in CSS3 and is supported by most modern browsers, but not by older versions of Internet Explorer.
  • Another possible cause is that the font file itself is corrupted or not properly formatted. In some cases, the font file may be missing crucial information required for IE 11 to render it correctly.

✅ Best Solutions to Fix It

Enabling Font Squirrel's Font Sailing

  1. Step 1: Step 1: Download and install Font Squirrel's Font Sailing extension for Internet Explorer. This tool will help you convert your custom font files into a format that IE 11 can understand.
  2. Step 2: Step 2: Once the extension is installed, open the website with the broken font in IE 11. The extension should automatically detect the font and offer to convert it. Click on 'Convert' to proceed.
  3. Step 3: Step 3: Wait for the conversion process to complete. This may take a few minutes depending on the size of the font file. Once the conversion is done, try loading the website again to see if the font renders correctly.

Using the @font-face hack

  1. Step 1: Step 1: Add the following code to the head section of your HTML document: @import url('https://fonts.googleapis.com/css?family=Your+Font+Name&display=swap'); This will import the font from Google Fonts and make it available for IE 11.
  2. Step 2: Step 2: Replace 'Your Font Name' with the actual name of the font you want to use. You can find this information on the Google Fonts website.

💡 Conclusion

By following these troubleshooting steps, you should be able to resolve the '@font-face encountered unknown error.' issue in Internet Explorer 11 on Windows 10. Remember to always test your websites in multiple browsers and versions to ensure compatibility. Happy coding!

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