Range

The HTTP Range request header specifies which portion of a resource the server returns in the response.

Table of Contents

Usage
Directives
Example
Takeaway
See also

Usage

The Range header enables partial retrieval of a resource. A client includes this header to request specific byte ranges instead of downloading the entire resource. This is essential for resuming interrupted downloads, Streaming media with seek support, and loading large files in parallel segments.

Before sending a range request, a client verifies server support by checking the Accept-Ranges header in a prior response. A value of bytes confirms the server handles byte-range requests. A value of none indicates the server does not accept range requests.

When a range request succeeds, the server responds with 206 Partial Content and includes the Content-Range header indicating the byte positions and total resource size. Multiple ranges in a single request produce a multipart response with each part carrying its own Content-Range and Content-Type headers.

If the requested range falls outside the resource boundaries, the server returns 416 Range Not Satisfiable. In some cases, the server ignores the Range header entirely and delivers the full resource with a 200 status.

Directives

unit

The unit specifies the measurement for ranges. bytes is the standard unit defined in the HTTP specification. Custom range units are permitted but rarely used.

range-start and range-end

The range-start value is the zero-based byte offset where the range begins (required). The range-end value is the zero-based byte offset where the range ends (optional). Omitting range-end requests all bytes from range-start to the end of the resource.

suffix-length

The suffix-length form requests the last N bytes of a resource. The format -N retrieves the final N bytes without needing to know the total resource size.

Example

A client requests the first 1,000 bytes of a large image file. The server responds with 206 Partial Content and specifies the byte range and total file size in the Content-Range header.

GET /photo.jpg HTTP/1.1
Host: cdn.example.re
Range: bytes=0-999

HTTP/1.1 206 Partial Content
Content-Type: image/jpeg
Content-Length: 1000
Content-Range: bytes 0-999/250000

A client resumes a download starting at byte 50,000. Omitting the end value requests everything from the given offset to the end of the resource.

Range: bytes=50000-

A client requests the last 500 bytes of a file. The suffix form is useful when the total file size is unknown to the client.

Range: bytes=-500

A client requests two separate byte ranges in a single request. The server returns a multipart response with each segment as a separate body part.

Range: bytes=0-499, 1000-1499

Takeaway

The Range header enables partial resource retrieval by specifying byte ranges, supporting download resumption, media streaming, and parallel segment fetching.