Preface
Recently, I was researching some things related to HTTP Cache, and I found myself confused by the different headers such as Pragma, Cache-Control, Etag, Last-Modified, Expires, etc. After reading many reference materials, I gained a deeper understanding. I thought that if I could understand Cache from a different perspective, it might be easier to understand what these headers are doing.
In the previous research materials, many articles explained the functions and parameters of each header one by one. However, I think that too many parameters can easily confuse beginners. Therefore, this article attempts to guide the usage scenarios and purposes of each header step by step through different questions. Also, because this article is for beginners, not all parameters will be discussed.
In fact, there are different opinions on Cache on the Internet. If there are any doubts, I will try to follow the standards written in the RFC. If there are any errors, please correct me. Thank you.