Downloading Images Best Practices

  • Clients should honor any cache control response headers provided by the server.

Downloading Custom Images

  • When fetching custom display images, we recommend against using this service as a download proxy. Instead use one of the following options:
    • Use the 'redirect' parameter. The 302 HTTP response will redirect the download request to the appropriate Yahoo servers hosting the image.
    • Use the HTTP HEAD request to obtain the image URL and fetch the image directly from its source.
  • For browser side cache busting, it is recommended to submit the checksum value within the request URI using '&chksum='.
  • Any image reformatting (re-sizing, etc.) overhead should be incurred client side. Formatting parameters such as 'height' and 'width' are to be used only by clients that cannot support client side image reformatting.
  • If using this service as a download proxy:
    • An image successfully download through this service will return a 200 OK with a custom 'X-Yahoo-msgr-ichecksum' response header.
    • The value embedded within this header represents a unique server hash (checksum) for the image, and can be used for client side caching of custom images

Downloading Avatar Images

  • It is recommended that clients fetch avatar images directly from the Yahoo Avatar servers instead of using this service as a proxy.
  • If this service is used as a proxy, we recommended against using this service as a download proxy. Instead use one of the following options:
    • Use the 'redirect' parameter. The 302 HTTP response will redirect the download request to the appropriate Yahoo servers hosting the image.
    • Use the HTTP HEAD request to obtain the image URL and fetch the image directly from its source.

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