compressResponse

Summary

Compresses a Response based on the client's Accept-Encoding header.

Compression is skipped for:

• Requests with no Accept-Encoding header (RFC 7231)
• Empty responses
• Already compressed responses
• Responses with Content-Length below threshold (default: 1024 bytes)
• Responses with Cache-Control: no-transform
• Responses advertising range support (Accept-Ranges: bytes)
• Partial content responses (206 status)

Responses eligible for content-coding negotiation include Accept-Encoding in the Vary header, even when identity is selected or the request does not include Accept-Encoding.

When compressing, this function:

• Sets Content-Encoding header
• Removes Content-Length header
• Sets Accept-Ranges to 'none'
• Converts strong ETags to weak ETags (per RFC 7232)

Signature

function compressResponse(
  response: Response,
  request: Request,
  options: CompressResponseOptions,
): Promise<Response>

Parameters

response

The response to compress

request

The request (needed to check Accept-Encoding header)

options

Optional compression settings

Returns

A response with the negotiated content coding and cache metadata