imgix completes several options in sequence when a purge is requested:
- The request is revalidated against the image in your Source. If the image is unchanged (returns a 304 status code), then the purge process stops. This is why any changes to an image, such as replacement or removal, have to start with your Master Image at the Source.
- If the image registers as changed, then it’s either removed or replaced by the new version in imgix’s origin cache.
- A request is then sent to the imgix CDN to set the image’s TTL to 0s, thus forcing revalidation on subsequent requests for both the Master Image and all derivatives.
Purging does not remove images from any of the following, because they are outside of the imgix system:
- Your Source (Amazon S3, Google Cloud Storage, etc.)
- Any third-party CDNs you might use in addition to the imgix CDN
- The end user’s browser cache
- Any ISP caches between imgix and the end user
Because of this, it is still possible for the end user to see an out-of-date image on occasion. Please contact Support if you need help with purging operations.