Miscellaneous · Request & Response

Upgrade

Requests a protocol upgrade (e.g. HTTP → WebSocket).

What is Upgrade?

The classic mechanism for switching protocols on an existing connection — most importantly HTTP/1.1 to WebSocket via `Upgrade: websocket`. Server responds with 101 Switching Protocols.

Typical usage

Set on WebSocket handshake requests.

Examples

Upgrade: websocket

Specification

RFC 9110 §7.8

Frequently asked questions

What is the Upgrade HTTP header?

The classic mechanism for switching protocols on an existing connection — most importantly HTTP/1.1 to WebSocket via `Upgrade: websocket`. Server responds with 101 Switching Protocols.

Is Upgrade a request or response header?

Upgrade can appear on both requests and responses. Set on WebSocket handshake requests.

What does a Upgrade header look like?

A typical Upgrade header looks like: Upgrade: websocket.

Related headers

Connection

Controls whether the network connection stays open after the current transaction.

X-Forwarded-For

The original client IP when behind a proxy or load balancer.

Forwarded

Standardized replacement for X-Forwarded-*.

Work with this header

cURL Converter →Turn a curl command into fetch / code and back.URL Parser →Break a URL into scheme, host, path and query.