HTTP 505 HTTP Version Not Supported — What It Means & How to Fix It

What Does This Error Mean?

A 505 HTTP Version Not Supported error means your browser and the website's server are using different versions of the rules that govern how they communicate. HTTP is a set of protocols — rules for talking between browsers and servers. The server got a request using a version of those rules it does not support. This is rare in everyday browsing. Most modern browsers and servers use compatible versions automatically.

Affected Models

All web browsers
All websites
Older browsers on older operating systems
Servers with outdated software

Common Causes

Your browser is very outdated and is using an old version of HTTP that the server no longer accepts
The web server is outdated and does not support the newer HTTP version your browser uses
A proxy server between you and the website is incompatible with the HTTP version being used
A browser extension is altering the HTTP version declared in the request
The website's server has a misconfigured HTTP settings file

How to Fix It

Update your browser to the latest version. Go to the browser's Settings > Help > About, and install any available updates.

An outdated browser is the most common visitor-side cause of this error.
Try a different browser. If the error only appears in one browser, that browser's version or settings are the issue.

Chrome, Firefox, and Edge all support modern HTTP versions and are free to download.
Clear your browser cache and cookies, then try again.

Cached data from an older protocol version can occasionally cause this error.
Disable browser extensions and try reloading.

Some extensions alter request headers including the HTTP version.
If you are on an older operating system like Windows 7 or XP, consider upgrading — modern browsers no longer support those systems fully.

Outdated operating systems prevent browsers from updating, which causes compatibility issues.

When to Call a Professional

If the fixes below do not resolve the issue, the problem is most likely on the website's server. Report it to the site's support team. Website owners should ensure their server software is updated and configured to support both HTTP/1.1 and HTTP/2 at minimum.

Frequently Asked Questions

What is HTTP and why does it have versions?

HTTP (HyperText Transfer Protocol) is the language browsers and web servers use to communicate. Like any software, it gets updated over time. HTTP/1.1 was the standard for decades. HTTP/2 is now common, and HTTP/3 is increasingly used. A 505 error means the two sides are using incompatible versions.

Is this error common?

No — it is quite rare in everyday browsing. Modern browsers and most modern servers are designed to negotiate compatible versions automatically. You are most likely to see it with very old software on either end.

Is updating my browser safe?

Yes — browser updates are safe, free, and important for security. Outdated browsers are vulnerable to attacks. Keeping your browser updated is one of the most important things you can do for online safety.