1--- 2c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. 3SPDX-License-Identifier: curl 4Long: header 5Short: H 6Arg: <header/@file> 7Help: Pass custom header(s) to server 8Protocols: HTTP IMAP SMTP 9Category: http imap smtp 10Added: 5.0 11Multi: append 12See-also: 13 - user-agent 14 - referer 15Example: 16 - -H "X-First-Name: Joe" $URL 17 - -H "User-Agent: yes-please/2000" $URL 18 - -H "Host:" $URL 19 - -H @headers.txt $URL 20--- 21 22# `--header` 23 24Extra header to include in information sent. When used within an HTTP request, 25it is added to the regular request headers. 26 27For an IMAP or SMTP MIME uploaded mail built with --form options, it is 28prepended to the resulting MIME document, effectively including it at the mail 29global level. It does not affect raw uploaded mails (Added in 7.56.0). 30 31You may specify any number of extra headers. Note that if you should add a 32custom header that has the same name as one of the internal ones curl would 33use, your externally set header is used instead of the internal one. This 34allows you to make even trickier stuff than curl would normally do. You should 35not replace internally set headers without knowing perfectly well what you are 36doing. Remove an internal header by giving a replacement without content on 37the right side of the colon, as in: -H `Host:`. If you send the custom header 38with no-value then its header must be terminated with a semicolon, such as -H 39`X-Custom-Header;` to send `X-Custom-Header:`. 40 41curl makes sure that each header you add/replace is sent with the proper 42end-of-line marker, you should thus **not** add that as a part of the header 43content: do not add newlines or carriage returns, they only mess things up for 44you. curl passes on the verbatim string you give it without any filter or 45other safe guards. That includes white space and control characters. 46 47This option can take an argument in @filename style, which then adds a header 48for each line in the input file. Using @- makes curl read the header file from 49stdin. Added in 7.55.0. 50 51Please note that most anti-spam utilities check the presence and value of 52several MIME mail headers: these are `From:`, `To:`, `Date:` and `Subject:` 53among others and should be added with this option. 54 55You need --proxy-header to send custom headers intended for an HTTP 56proxy. Added in 7.37.0. 57 58Passing on a "Transfer-Encoding: chunked" header when doing an HTTP request 59with a request body, makes curl send the data using chunked encoding. 60 61**WARNING**: headers set with this option are set in all HTTP requests - even 62after redirects are followed, like when told with --location. This can lead to 63the header being sent to other hosts than the original host, so sensitive 64headers should be used with caution combined with following redirects. 65
