Is there an app to watch movies together online with live chat (and voice)?

Teleparty (the old Netflix Party) is the classic and it's free, the sync is solid for Netflix, Prime, Disney+ and a few others. The catch for your exact ask: it's a desktop Chrome extension only and the chat is text plus emoji, no voice. So on your phone it's a non-starter, and you'd still need a separate call for talking. Great tool, just not the all-in-one mobile-plus-voice thing you're after.

Seconding the voice point. We did Teleparty plus a Discord call for a year and the audio drift drove us nuts, you pause the film but the call keeps going. Switched after reading the watch party app roundup here and having voice tied to the same sync engine fixed it. Kosmi is another option worth knowing, it runs a shared virtual browser in the page so it works on mobile browsers and has video chat, but quality dips on heavier streams and you're all watching one piped feed rather than your own logins.

If you want the streaming-service breakdown before committing, the best apps to watch movies together comparison lays out which app supports which service. Rave is mobile-first with voice and text too, worth a look, though its iOS availability has been hit or miss lately. For Netflix specifically there's also a remote Netflix walkthrough that covers the everyone-needs-their-own-login thing, which trips people up.

Update for anyone finding this later: we went with Watchly and it's exactly what I wanted. I was on my phone, he was on his laptop, Netflix synced perfectly and the push-to-talk voice meant we could just chat without juggling a second app. The live reactions are stupidly fun too. One heads-up the thread was right about, you do each need your own Netflix and Prime login, but that was never a problem for us. Thank you all.