If-Range

The If-Range HTTP request header makes a range request conditional: if the condition is fulfilled, the range request will be issued and the server sends back a 206 Partial Content answer with the appropriate body. If the condition is not fulfilled, the full resource is sent back, with a 200 OK status.

This header can be used either with a Last-Modified validator, or with an ETag, but not with both.

The most common use case is to resume a download, to guarantee that the stored resource has not been modified since the last fragment has been received.

Header type	Request header
Forbidden header name	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") and may be prefixed by W/ to indicate that the weak comparison algorithm should be used.

<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 

Specifications

Specification	Title
RFC 7233, section 3.2: If-Range	Hypertext Transfer Protocol (HTTP/1.1): Range Requests

Browser compatibility

See also

• ETag
• Last-Modified
• If-Modified-Since
• If-Unmodified-Since
• If-Match
• If-None-Match
• 206 Partial Content
• HTTP Conditional Requests