428 Precondition Required

The server requires the request to be conditional, such as with If-Match.

Code: 428
Reason phrase: Precondition Required
Class: 4xx Client error
Defined in: RFC 6585 section 3
Cacheable by default: No

What it means

Client error: the problem lies with the request. Repeating it unchanged will normally fail again.

Common causes. APIs that protect against lost updates.

What to do. Fetch the resource, then send its ETag in If-Match.

How clients and crawlers treat it

Google Search. Like every 4xx except 429, it tells Google the content does not exist: an indexed URL is removed from the index, and a new one is not processed. Crawl frequency for the URL gradually drops. Source: Google Search Central, How HTTP status codes, and network and DNS errors affect Google Search.

Caching. Not cacheable by default (RFC 9110 section 15.1 does not list it). A cache stores it only when the response says so with Cache-Control or Expires.

Example response

HTTP/1.1 428 Precondition Required
Content-Type: text/plain; charset=utf-8

Precondition Required

How to send 428

nginx

location /example {
    return 428;
}

Apache (.htaccess)

RewriteEngine On
RewriteRule ^example$ - [R=428,L]

PHP

http_response_code(428);
echo 'Precondition Required';
exit;

Node.js

res.writeHead(428, { 'Content-Type': 'text/plain' });
res.end('Precondition Required');

Python (Flask)

# in a view function
return 'Precondition Required', 428

Change the paths to suit. In nginx, add_header needs always to apply to error responses.

Related codes

All status codes · All 4xx codes

Names and numbers from the IANA HTTP Status Code Registry. Google Search behaviour as documented by Google Search Central.