HTTP 426 Upgrade Required — What It Means & How to Fix It

The HTTP 426 Upgrade Required status code indicates the server refuses to perform the request using the current protocol and requires the client to upgrade to a different protocol. This guide covers everything you need to know about this topic, including common causes, step-by-step solutions, and answers to frequently asked questions.

Here are the key things to understand: The server must send an Upgrade header indicating which protocol is required.. Common when a server requires TLS/HTTPS instead of plain HTTP.. The client should switch to the specified protocol and retry.. Different from 101 Switching Protocols, which is a successful upgrade.. Understanding these fundamentals will help you diagnose and resolve this issue more effectively.

The most common reasons this occurs include: The server requires HTTPS but the request was made over HTTP.. The server requires a newer version of the HTTP protocol.. An API endpoint requires WebSocket but received a regular HTTP request.. Identifying the root cause is the first step toward finding the right solution.

To resolve this, follow these recommended steps: Check the Upgrade header in the response for the required protocol.. Switch to HTTPS if the server requires a secure connection.. Upgrade your client to support the required protocol version.. Update the URL scheme from http:// to https:// if TLS is required.. If these steps do not resolve the issue, consider consulting additional resources or a qualified professional.

This article is part of our HTTP Status Codes collection on Error Codes Wiki. We provide comprehensive, up-to-date information to help you find solutions quickly.