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HTTP Header
If-Match
CachingMakes the request conditional on the resource matching the given ETag value.
HTTP header reference, syntax, examples, and developer usage.
What is the If-Match header?
The If-Match HTTP header is used to transmit metadata between a client and server as part of HTTP requests or responses.
HTTP headers define how content should be interpreted, cached, authenticated, secured, or processed by browsers and APIs.
Direction
This header may appear in both HTTP requests and responses.
Syntax
If-Match: "etag-value"
Example
If-Match: "abc123"
Common use cases
- Optimistic locking
- Safe updates
- Preventing lost updates
Common mistakes
- Using the header in the wrong request or response context
- Sending invalid header values
- Incorrect header syntax
- Assuming the header automatically changes server behaviour