Caching & Performance

Last-Modified

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An HTTP response header indicating when the resource was last changed, used with If-Modified-Since for conditional requests and cache validation.

Related Protocols

HTTP

Mentioned in Guides

HTTP Caching: Cache-Control, ETags, and 304 Responses HTTP Fundamentals

Essential HTTP Headers Every Developer Should Know HTTP Fundamentals

HTTP Conditional Requests: If-Match, If-None-Match, and Beyond HTTP Fundamentals

RFC 7231/9110: HTTP Method Semantics — Safe, Idempotent, and Cacheable Protocol Deep Dives

See Also

Conditional Request HTTP Concepts

Cache-Control Caching & Performance

ETag (Entity Tag) Caching & Performance

Conditional Headers Web Standards