Nocache

Nocache is a term used in web development to describe techniques and header directives intended to prevent or limit the caching of a resource by browsers and intermediate caches. It is not a single standard, but part of the HTTP caching system that governs how responses are stored and reused.

The primary mechanisms are HTTP headers that control caching behavior. Cache-Control: no-store instructs caches not to store the response at all. Cache-Control: no-cache allows caching but requires revalidation with the origin server before the cached copy can be used. Cache-Control: max-age=0 and related directives can trigger revalidation in some contexts. For compatibility with older systems, HTTP/1.0-like directives such as Pragma: no-cache and Expires: 0 may also be used. The No-cache directive means the cached data can be reused only after a fresh check with the server, typically using conditional requests (If-Modified-Since, If-None-Match). No-store explicitly forbids storing the response, even temporarily.

The use of nocache controls is important for dynamic or sensitive content, personalized pages, and resources that must reflect the most recent data. However, it can reduce performance by increasing requests to the origin server and lowering cache benefits. Behavior can vary across browsers and intermediate caches (CDNs), which may interpret directives differently or apply their own policies.

Implementation often involves setting appropriate headers on responses from the server or configuring web frameworks to mark certain routes or resources as nocache. Developers should verify headers with tools and consider cache-busting strategies for static assets when caching is desirable.