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If-Range header

The HTTP If-Range {{Glossary("request header")}}header makes a range request conditional. If the condition is fulfilled, a range request is issued, and the server sends back a {{HTTPStatus("206", "206 Partial Content")}}Content response with part (or parts) of the resource in the body. If the condition is not fulfilled, the full resource is sent back with a {{HTTPStatus("200", "200 OK")}}OK status.

This header can be used either with the {{HTTPHeader("Last-Modified")}}Modified validator or with {{HTTPHeader("ETag")}}ETag, but not with both.

The most common use case is to resume a download with guarantees that the resource on the server has not been modified since the last part has been received by the client.

Header type {{Glossary("[Request header")}}header](https://developer.mozilla.org/en-US/docs/Glossary/Request%20header)
{{Glossary("[Forbidden request header")}}header](https://developer.mozilla.org/en-US/docs/Glossary/Forbidden%20request%20header) No

Syntax

If-Range: <day-name>, <day> <month> <year> <hour>:<minute>:<second> GMT
If-Range: <etag>

Directives

  • <etag>
    • : An entity tag uniquely representing the requested resource. It is a string of ASCII characters placed between double quotes (Like "675af34563dc-tr34"). A weak entity tag (one prefixed by W/) must not be used in this header.
  • <day-name>
    • : One of Mon, Tue, Wed, Thu, Fri, Sat, or Sun (case-sensitive).
  • <day>
    • : 2 digit day number, e.g., "04" or "23".
  • <month>
    • : One of Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec (case sensitive).
  • <year>
    • : 4 digit year number, e.g., "1990" or "2016".
  • <hour>
    • : 2 digit hour number, e.g., "09" or "23".
  • <minute>
    • : 2 digit minute number, e.g., "04" or "59".
  • <second>
    • : 2 digit second number, e.g., "04" or "59".
  • GMT
    • : Greenwich Mean Time. HTTP dates are always expressed in GMT, never in local time.

Examples

If-Range: Wed, 21 Oct 2015 07:28:00 GMT

If-Range: "67ab43"

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also