Meziantou.Framework

Default no-cache header

edit

UseNoCache adds Cache-Control: no-cache,no-store,must-revalidate to the responses that do not define Cache-Control:

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

app.UseNoCache();

app.MapGet("/", static () => "Hello World!");

app.Run();

Without a Cache-Control header, browsers and proxies may decide on their own to cache a response (heuristic caching), and a user can see an outdated page or API result. With this middleware, caching is something an endpoint opts into.

Behavior

  • A response that sets its own Cache-Control is never modified. An empty value counts as not set.
  • When the response has already started, the header is left alone rather than failing the request.
  • no-store prevents any cache from keeping the response, including UseResponseCaching, UseOutputCache and a CDN.

Placement

Register UseNoCache after the middleware that serve cacheable content, such as UseStaticFiles. The static file middleware sets ETag and Last-Modified but no Cache-Control: when UseNoCache runs first, every static file becomes non-cacheable.

To cache an endpoint, set the header in the endpoint, for instance with context.Response.Headers.CacheControl = "public, max-age=3600", or with the response caching or output caching features of ASP.NET Core that set it.