I pay for Netflix Premium but was stuck at 1080p. Turns out Netflix layers multiple capability checks before serving 4K: user agent, screen resolution, Media Capabilities API, codec support, DRM robustness negotiation, and their Cadmium player's internal bitrate caps.

Built an extension that spoofs all of these. The interesting discovery: you have to intercept every layer. Miss one and you're back to 1080p.

Here's the catch though. Even with all the JavaScript spoofs working, Chrome still won't get 4K. Netflix requires Widevine L1 (hardware DRM), and Chrome only has L3 (software). The browser literally can't negotiate the security level Netflix wants. Edge on Windows has L1, so the extension actually delivers 4K there.

So what's the point on Chrome? Honestly, not much for 4K specifically. But the reverse-engineering was the interesting part. Understanding how Netflix fingerprints devices and decides what quality to serve. The codebase documents all the APIs they check.

On Edge: works reliably, getting 3840x2160 at 15000+ kbps. On Chrome: spoofs work, DRM negotiation fails, stuck at 1080p.

The repo has detailed documentation on what each spoof does and why. Happy to discuss the technical approach or answer questions.