0-byte response when Firefox privacy pass enabled

jasom

With Kagi Privacy Pass enabled on Firefox, loading kagi.com (even without a search, but also with a search) always returns a status 200, 0-byte response. Privacy pass was previously working on this browser about a week ago.

Headers in the response are below; I elided the two base-64 strings in the www-authenticate header in case they are sensitive

HTTP/2 200 
www-authenticate: PrivateToken challenge=<base-64-string>, token-key=<another-base-64-string>
vary: origin, access-control-request-method, access-control-request-headers
access-control-allow-origin: *
access-control-expose-headers: www-authenticate
x-cloud-trace-context: 8ba32ea61d6aebf6168309787a43db3c
date: Tue, 04 Aug 2026 13:03:47 GMT
content-type: text/html
server: Google Frontend
content-length: 0
via: 1.1 google
alt-svc: h3=":443"; ma=2592000,h3-29=":443"; ma=2592000
X-Firefox-Spdy: h2

I expected kagi.com to load with content, and for search to work.

pixel

Hey there,

In the short term, you should be able to go into the extension settings and reset state.
Upon regenerating tokens, it should work again.
I was able to reproduce this, but resetting state fixed it for me.

We'll look into this.

AlexDermer

The Problem

I am running Firefox version 153.0.1 on Linux with Kagi search and privacy pass which has always worked perfectly as intended until today. Today when I turned privacy pass on it showed a status of Ready. I typed a search into the address bar of Firefox - this has worked historically - and when I pressed enter I was presented with a blank white page. Viewing the source of the page showed a 1.

Replication

Unfortunately, I do not know exactly how to replicate this issue. My hunch is that Firefox was updated between the last time I used Privacy Pass and today, it had been a few weeks. I suppose it may have also been due to the extended time since I last used it.

I have found a temporary workaround, I will describe it below, but I wanted to make sure this is documented as it seems hard to catch. I searched for similar issues and did not see anything matching this one, but I apologize if this is a duplicate.

Troubleshooting and Investigation

The first thing I tried was turning the extension off and back on again which did fix the searches not resolving, the searches did resolve fine when the extension was off.

I then tried logging out of Kagi and back in, this also failed to resolve the issue. I also tried discarding the token, but that was not the answer either.

The (Temporary) Fix

Reset the Privacy Pass extension, then reconfigure Privacy Pass with your session link (found here: https://kagi.com/settings/user_details). For me that was enough to get it working again although this took quite awhile to figure out. Hopefully I can save others some time and also get this on the developers radar. This is the first time it has happened.

I expected it to search with Kagi and load the results pages as it has always done previously.