What is the HTTP HEAD method?
HEAD is one of the request methods a browser or other client can send to a web server. It asks for exactly what a GET request for the same URL would return, except that the server sends back only the status line and the response headers, never the body. The client learns whether the resource is there and what it is (its type, its size and when it last changed) without downloading it.
Not to be confused with the read/write head inside a hard drive, the part on the actuator arm that reads and writes the platters. That has its own glossary page.
What it's used for
- Checking that a resource exists. A 200 OK status means it's there; a 404 Not Found means it isn't.
- Finding a file's size before downloading it. The Content-Length header usually reports how many bytes a GET would return.
- Cache checks. The Last-Modified and ETag headers show whether a resource has changed since a copy was saved.
- Link checkers and uptime monitors. Tools that test many URLs, or poll a site every few minutes, can use HEAD to save bandwidth.
- Troubleshooting. Headers reveal redirects (a 301 or 302 status with a Location header), the content type and security headers.
From a command line, curl -I https://www.example.com sends a HEAD request and prints the headers.
HTTP methods compared
| Method | What it does | Changes data on the server? |
|---|---|---|
| GET | Retrieves a resource, such as a web page or image, with its body | No |
| HEAD | Same as GET, but returns the headers only | No |
| POST | Sends data to the server, such as a submitted form or a file upload | Yes |
| PUT | Uploads or replaces a resource at a specific URL | Yes |
| DELETE | Removes a resource from the server | Yes |
GET and HEAD are called safe methods because they only read. A server must not send a body in reply to HEAD, even when the GET for the same URL would return one.
For the CompTIA A+ exam
Core 1 (220-1201) objective 2.3 lists web servers among the server roles, and objective 2.1 covers HTTP on port 80 and HTTPS on port 443. HTTP methods aren't named in the objectives, but knowing the basic ones helps with web server scenarios: GET fetches a page, POST submits a form, and HEAD fetches only the headers. If a question about storage mentions a drive head, it means the hard drive's read/write head instead.