---
title: "101 Switching Protocols — what it means and how to fix it"
description: "The connection is being upgraded from HTTP to another protocol, usually WebSockets. What causes an HTTP 101, what to try as a visitor, and what to check if it is your own site."
url: https://atoneplace.net/error/101/
site: "At One Place"
---

# HTTP 101 — Switching Protocols

**HTTP 101: Switching Protocols**

The connection is being upgraded from HTTP to another protocol, usually WebSockets.

## What 101 actually means

The client asked to change protocols on the existing TCP connection using an `Upgrade` header, and the server agreed. In practice this almost always means a WebSocket is being opened: the page requested `Upgrade: websocket`, got a 101 back, and from that point on the connection carries WebSocket frames rather than HTTP messages. Seeing 101 in a network panel next to a long-lived connection is normal and healthy.

## Common causes

- A WebSocket connection is being established
- A client requested an upgrade to HTTP/2 over cleartext (h2c)
- A tunnelling protocol is negotiating over an existing HTTP connection

## If you're just trying to view the page

1. Nothing — this is a successful connection, not an error
2. If live features on a page do not work, a corporate proxy or firewall may be blocking the upgrade entirely, which would show as a failure rather than a 101

## If it's your site

1. If WebSockets fail behind a reverse proxy, make sure it forwards `Upgrade` and `Connection` headers — Nginx needs `proxy_set_header Upgrade $http_upgrade;` and `proxy_set_header Connection "upgrade";`
2. HTTP/1.1 is required for the upgrade dance; a proxy that downgrades the connection will break it
3. Check `proxy_read_timeout` — the default of 60 seconds kills idle WebSockets

## Reference

- **Status code:** 101
- **Reason phrase:** Switching Protocols
- **Category:** 1xx — Informational
- **Defined in:** RFC 9110 §15.2.2

## Common questions

### What does HTTP 101 mean?

The connection is being upgraded from HTTP to another protocol, usually WebSockets. The client asked to change protocols on the existing TCP connection using an `Upgrade` header, and the server agreed. In practice this almost always means a WebSocket is being opened: the page requested `Upgrade: websocket`, got a 101 back, and from that point on the connection carries WebSocket frames rather than HTTP messages.

### How do I fix a 101 error?

Nothing — this is a successful connection, not an error

### Is 101 a client error or a server error?

101 is in the 1xx range, which means informational. It is not an error at all.

## Related pages

- [103 Early Hints](https://atoneplace.net/error/103/)
- [100 Continue](https://atoneplace.net/error/100/)
- [102 Processing](https://atoneplace.net/error/102/)
- [104 Upload Resumption Supported](https://atoneplace.net/error/104/)

## Sources

- Hypertext Transfer Protocol (HTTP) Status Code Registry — IANA (https://www.iana.org/assignments/http-status-codes/)
- RFC 9110: HTTP Semantics — IETF (https://www.rfc-editor.org/rfc/rfc9110.html)