ETag

An ETag (Entity Tag) is a unique identifier assigned by a web server to a specific version of a resource, like a webpage or image. When you visit that resource again, your browser compares its stored ETag with the current one on the server. If they match, the server knows your copy is up-to-date and doesn't resend the entire content, saving time and bandwidth. If they differ, the server sends the latest version. ETags help improve website performance and ensure you see the latest content without unnecessary data transfer.