What types of HTTP requests are suitable for caching on the server or client?

For caching on the server or client side, HTTP request types like GET and sometimes HEAD are usually suitable.

• GET — the main method for retrieving resources, which by default is considered idempotent and safe, so its results can be cached.
• HEAD — similar to GET but only returns headers without a body, and can also be cached.

Other methods such as POST, PUT, DELETE, PATCH are generally not cached because they modify the server state and are not considered safe for repeated use without changes.

Caching is controlled by HTTP headers, for example:

• Cache-Control — defines caching rules (max-age, no-cache, etc.)
• ETag and Last-Modified — allow the client to verify cache freshness

Example of a header for caching a GET request:

Cache-Control: public, max-age=3600

This means the response can be stored in cache for an hour.