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MDN / Origin header

The HTTP Origin indicates the (scheme, hostname, and port) that caused the request. For example, if a user agent needs to request resources included in a page, or fetched by scripts that it executes, then the origin of the page may be included in the request.

Syntax

Origin: null
Origin: <scheme>://<hostname>
Origin: <scheme>://<hostname>:<port>

Directives

  • null

    <scheme>

    • : The protocol that is used. Usually, it is the HTTP protocol or its secured version, HTTPS.

    <hostname>

    • : The domain name or the IP address of the origin server.

    <port>

    • : Port number on which the server is listening. If no port is given, the default port for the requested service is implied from the scheme (e.g., 80 for an HTTP URL).

Description

The Origin header is similar to the header, but does not disclose the path, and may be null. It is used to provide the security context for the origin request, except in cases where the origin information would be sensitive or unnecessary.

Broadly speaking, user agents add the Origin request header to:

  • requests.

  • same-origin requests except for or requests (i.e., they are added to same-origin , , , , and requests).

There are some exceptions to the above rules; for example, if a cross-origin or request is made in no-cors mode, the Origin header will not be added.

The Origin header value may be null in a number of cases, including (non-exhaustively):

  • Origins whose scheme is not one of http, https, ftp, ws, wss, or gopher (including blob, file and data).

  • Cross-origin images and media data, including that in <img>, <video> and <audio> elements.

  • Documents created programmatically using createDocument(), generated from a data: URL, or that do not have a creator browsing context.

  • Redirects across origins.

  • Documents served with the sandbox directive whose value doesn’t include allow-same-origin.

  • iframes with a sandbox attribute whose value doesn’t include allow-same-origin.

  • Responses that are network errors.

  • Certain values, for requests that use neither GET nor HEAD and aren’t made in cors mode (e.g., basic form posts). See Effect on the Origin header for the policy values that trigger this.

There is a more detailed listing of cases that may return null on Stack Overflow: When do browsers send the Origin header? When do browsers set the origin to null?

Examples

Origin: https://developer.mozilla.org

Origin: https://developer.mozilla.org:80

Specifications

Browser compatibility

See also