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If-Range header

files/en-us/web/http/reference/headers/if-range/index.md

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The HTTP If-Range {{Glossary("request 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")}} 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")}} status.

This header can be used either with the {{HTTPHeader("Last-Modified")}} validator or with {{HTTPHeader("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.

<table class="properties"> <tbody> <tr> <th scope="row">Header type</th> <td>{{Glossary("Request header")}}</td> </tr> <tr> <th scope="row">{{Glossary("Forbidden request header")}}</th> <td>No</td> </tr> </tbody> </table>

Syntax

http
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

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

If-Range: "67ab43"

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

  • HTTP Conditional Requests guide
  • {{HTTPHeader("ETag")}}
  • {{HTTPHeader("Last-Modified")}}
  • {{HTTPHeader("If-Match")}}, {{HTTPHeader("If-Modified-Since")}}, {{HTTPHeader("If-Unmodified-Since")}}, {{HTTPHeader("If-None-Match")}} conditional request headers
  • {{HTTPStatus("206", "206 Partial Content")}}, {{HTTPStatus("412", "412 Precondition Failed")}}, {{HTTPStatus("416", "416 Range Not Satisfiable")}} response status codes