Articles/HTTP

HTTP 426 Upgrade Required — What It Means

What HTTP status code 426 Upgrade Required means, when servers return it, and how to handle it correctly.

Published September 25, 2026

HTTP 426 Upgrade Required — The client should switch to a different protocol to complete the request.

Key points

  • The server refuses to complete the request using the current protocol version
  • Commonly seen when a server requires HTTPS and the client attempted a plain HTTP request
  • Paired with an Upgrade header specifying the required protocol
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