What is a From header?
The email address of the person controlling the requesting user agent, mostly used by web crawlers.
From is mostly seen on requests from well-behaved web crawlers and bots, giving a website operator a contact address if that automated traffic starts causing problems. It's rarely sent by browsers or typical API clients, so seeing it in your server logs is usually a reliable signal that the request came from a crawler rather than a real visitor - useful context when you're trying to distinguish legitimate uptime-monitoring or search-engine traffic from the rest.
Common use case
A well-behaved web crawler includes a contact email in From, so a site operator whose server is being hit too hard has someone to reach out to before blocking the bot outright.
Example
From: [email protected]History
Part of the original HTTP/1.0 specification, RFC 1945 (1996).
Did you know?
It's one of the oldest and least-used headers in the entire spec - almost no browser has ever sent it by default, since revealing a user's email address on every request was a privacy concern even in 1996.