This is not necessarily Firefox, but because reCAPTCHA is designed to be more frictionless if Google can identify the user.

If you have their tracking cookies, if you don't use a VPN, and if you block ads (which would have more tracking cookies), Google's certainty of who you are is higher, increasing the chance that you are a human.

Firefox's default settings, especially with the new Content Blocking features, are enough for reCAPTCHA to be less sure you're a human, and try to make you prove it more often.

So Google manages to sell a product (reCAPTCHA), show good intentions (bot-prevention), increase usage of Chrome (because it's a smoother experience through reCAPTCHA), and get more information on everyone.

Win x4

Google seems to have intentionally tuned reCAPTCHA to punish anyone who isn't a Google customer or is blocking Google's tracking cookies. This is a win for nobody except Google.

So you think the browser choice is relevant? Sounds like discrimination of users who use a competitors product... (probably illegal).

I mean, I have noticed those harder captures too since I switched to Firefox, but I didn't realize it was due to the different browser. I thought it was just a newer version.

I assume that recaptcha classifies you as human faster if you use Chrome and are logged into your google account with it

I use Firefox with uBlock Origin, Privacy Badger, Google Container and Decentraleyes and am not signed into Google. ReCAPTCHA is an absolute nightmare under these conditions. It's sad because there is one site I absolutely need that has ReCAPTCHA when logging in. I literally keep another browser (Opera) around with no extensions just so I can log into that one site.

I sometimes use Random User-Agent as well to resist fingerprinting; this makes ReCAPTCHA not just extremely tedious (up to about 10 rounds of sl-o-o-o-wly fading pictures) but literally impossible (it never ends).

I've had this happen to me in Chrome when logged out over VPN

Could this be considered a violation of net neutrality?

Not really. Network neutrality, to be precise, is about not treating network packets differently based on who is sending or receiving them. It has nothing to do with what happens at the application level.