Skip to main content
The information on this page should be used for troubleshooting purposes only. Clients should not rely on these headers or error codes, as they may change in the future.

​
Response headers

Responses from the Bunny Optimiser may include the following headers:
  • X-DownloadSize: Size of the original asset downloaded from the origin
  • X-BO-CompressionRatio: Percentage reduction in size of the final asset compared to the original
  • X-BO-OriginDownloadTime: Time spent downloading files from the origin (including the watermark, if present), in milliseconds
  • X-BO-ProcessingTime: Time spent on local processing, in milliseconds
  • X-BO-Processing-Error: Lists any errors that occurred while processing the request (see below)

​
Error codes

The following errors may be returned as the value of the X-BO-Processing-Error header.

​
General errors

  • 101 → An unknown error occurred
  • 102 → The original source file could not be downloaded from the origin
  • 103 → The source image could not be decoded or parsed as a valid image
  • 104 → Optimisation was skipped or failed because the output became larger than the original
  • 105 → The GIF file is invalid or cannot be processed
  • 106 → Text-based content could not be minified successfully
  • 107 → The requested output format is not supported
  • 200 → The watermark image could not be retrieved from its origin
  • 201 → The watermark origin request was cancelled before completion
  • 202 → The watermark image could not be decoded or parsed as a valid image
  • 204 → The watermark image URL returned a 404 Not Found response

​
Processing constraints

  • 301 → The generated or requested WebP image exceeds the allowed size limit
  • 302 → The requested resize would upscale the image, but upscaling is not enabled
  • 303 → The requested upscale exceeds the allowed limit
  • 304 → The AVIF output image exceeds the allowed size limit and was encoded in another format instead
Last modified on June 8, 2026