Content Transformation Error when accessing my site from a proxy

I host a personal website at (or if you prefer). My friend who works at a place with a secure proxy can’t access it, instead getting a white screen with the following error in Firefox:

Content Transformation Error (transformation_error)
Proxy cannot apply content transformation.
This could be caused by a misconfiguration, or possibly a response with an unknown content encoding.
For assistance, contact your network support team.

This isn’t a huge issue by itself, but I’d like people who work in secure environments like this to be able to access my site as I am applying for jobs in similar places.

The first few search results (1 and 2) indicate this may be related to Brotli compression, which Netlify uses as of May 2020.

Since there is no option as of the moment to disable Brotli compression in Netlify (assuming that is the root cause of the error), is there anything else I can do to make my site accessible to people working from secure proxies?

Hi, @MAKR. First, I’m going to discuss this as if the root cause is indeed the Brotli compression. I don’t have proof that this is the case and I just wanted to acknowledge that this is an assumption (for me), not a proven fact.

If this assumption is true (and I believe it is) the following seems to be the case:

  1. The proxy returns this error with Brotli compressed content.
  2. The web browser making the request is sending a header asking for Brotli compression.
  3. At Netlify, we have no way to know there is a proxy in use.
  4. If the Brotli encryption is requested, that is what Netlify sends.

With those being the facts, I don’t see a simple solution at Netlify at this time. We can enter a feature request for this:

  • There should be a site setting to disable Brotli on a per-site basis.

Would you like for us to enter that feature request?

On the proxy side (not at Netlify), there are two solutions:

  1. The proxy is updated to correctly handle Brotli compressed content.
  2. The proxy can modify the HTTP request header to remove Brotli from the list of allowed compression methods. If we don’t see it Brotli listed, we won’t send it as Brotli.

​Please let us know if there are any questions of it the feature request should be entered.

1 Like

Hello @luke! Thank you for the reply and run-down of how Brotli works. It’s probably a buggy proxy/browser combo that has the accidental upside of keeping employees off YouTube :wink:

I would appreciate a per-site Brotli toggle, so please enter that feature request. I’m probably at the bottom of the totem pole as a free user, but it would also help the handful of people using Bridgy for social media plugins. Thanks again!