406 Not Acceptable

406

Not Acceptable

Example HTTP Response

HTTP Response

HTTP/1.1 406 Not Acceptable
Content-Type: application/json

{"available": ["application/json", "application/xml"]}

Common Causes

Accept header doesn't match available formats
Language not supported
Content negotiation failed

Technical Details

What does this mean?

Picky eater alert! You asked for something in a format the server can't serve. Like ordering sushi at a pizza place.

Technical Definition

The server cannot produce a response matching the list of acceptable values defined in the request's headers.

RFC Says

"The 406 (Not Acceptable) status code indicates that the target resource does not have a current representation that would be acceptable to the user agent, according to the proactive negotiation header fields received in the request, and the server is unwilling to supply a default representation."

Plain English:

The server can't produce a response in any of the formats you requested via Accept headers. For example, if you requested JSON (Accept: application/json) but the server only provides XML, it returns 406.

Common Misinterpretation

Most servers ignore Accept headers or send a default format instead of returning 406. Strict adherence to content negotiation with 406 is rare in practice. Many APIs just return JSON regardless of Accept headers.

View RFC Documentation

Code Snippets

Ready-to-use code for returning this HTTP status in your application:

Node.js

// Express.js
app.get('/example', (req, res) => {
  res.status(406).json({
    error: 'Not Acceptable',
    message: 'Your error message here'
  });
});

// Native HTTP
const http = require('http');

http.createServer((req, res) => {
  res.writeHead(406, { 'Content-Type': 'application/json' });
  res.end(JSON.stringify({
    error: 'Not Acceptable',
    message: 'Your error message here'
  }));
}).listen(3000);

406 Not Acceptable FAQ

What causes a 406 Not Acceptable error?

Accept header doesn't match available formats. Language not supported. Content negotiation failed.

// Express.js app.get('/example', (req, res) => { res.status(406).json({ error: 'Not Acceptable', message: 'Your error message here' }); }); // Native HTTP const http = require('http'); http.createServer((req, res) => { res.writeHead(406, { 'Content-Type': 'application/json' }); res.end(JSON.stringify({ error: 'Not Acceptable', message: 'Your error message here' })); }).listen(3000);