What is ETag?
The ETag (Entity Tag) header is used to uniquely identify the version of a file. It allows web browsers and CDNs to determine whether a cached version of a file is still valid. If a file changes, the ETag changes as well, making it a powerful tool for efficient caching and reducing bandwidth usage.
How Bunny.net Handles ETag Headers
Yes, Bunny.net does support the ETag header, with a few important considerations:
- If your origin server includes an ETag header in its response and the “Optimize for Video Delivery” option is disabled, Bunny.net will pass through the ETag and cache the resource accordingly.
- If Bunny.net applies compression to the file (such as Brotli or Gzip), the ETag will be converted into a “weak” ETag. In this case, you’ll see a W/ prefix in front of the ETag string.
For example:
ETag: "123456789"
↓
ETag: W/"123456789"
This ensures compatibility with HTTP caching mechanisms while acknowledging that compression may slightly alter the binary output of the file.