Request

HTTP If-None-Match Header

Makes the request conditional. The server responds with 304 Not Modified if the resource's ETag matches the provided value. Otherwise returns the full resource with 200.

Purpose

Enables efficient cache validation by checking if a resource has changed via its ETag. Saves bandwidth by avoiding full downloads of unchanged content.

If-None-Match: "<etag-value>" If-None-Match: "<etag1>", "<etag2>" If-None-Match: *

Code Examples

See how to use the If-None-Match header in different tools and languages.

curl -I -H 'If-None-Match: "33a64df551425fcc55e4d42a148795d9f25f89d4"' \
  https://api.example.com/resource
# Response: 304 Not Modified (or 200 with new content)

Related Headers

ETag

An identifier for a specific version of a resource. Used for cache validation and conditional requests to avoid re-downloading unchanged content.

If-Modified-Since

Makes the request conditional. The server responds with 304 Not Modified if the resource has not been modified since the specified date.

Cache-Control

Specifies caching directives for both requests and responses. Controls how and for how long content is cached by browsers and intermediate caches.

Test Your APIs

API Response Time Checker

Test your APIs and inspect response headers in real-time

HTTP Headers Reference

Complete reference of all HTTP request and response headers

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