What are safe and unsafe HTTP methods? Why are they called so?

Safe HTTP methods are methods that do not change the state of the server, meaning they can be performed without the risk of side effects. These include, for example, GET, HEAD, OPTIONS, TRACE. They are called safe because they are intended only for retrieving data.

Unsafe methods are those that can change the state of the server, such as POST, PUT, DELETE, PATCH. They are called unsafe because they can create, modify, or delete resources, and their invocation may have side effects.