Building a random chat where language doesn't matter: WebRTC, relay as a condition, and live translated captions

The original Omegle proved something for fourteen years: two strangers who would never have met can have a good conversation. It shut down in 2023. What it never solved is the part I kept running into myself — most of the world still can't understand each other. You get matched with someone in São Paulo or Jakarta, you both say "hi", and that's where it ends. So I built Veilr: a random chat — text, voice or video — where your messages can arrive in the other person's language, and on a call you read live captions of what they say, translated into yours. It runs in the browser in 16 interface languages and on Android. I'm the only developer. This is the engineering story: the parts I'd tell a friend over coffee, including the ones that broke. Three formats, one idea Text, voice and video are different transports, but the product rule is the same: the other person should be able to understand you without either of you doing anything. Text. When the language you've set the app to differs from your partner's, your message is translated before delivery (Gemini does the translation). The original is always one tap away, because a translation you can't check is a translation you can't trust. The allowance belongs to the person reading the translation, and when it runs out the message is delivered exactly as typed — nothing is silently dropped. Voice and video. A streaming speech-to-text pipeline (Soniox) produces captions translated into the listener's language, rendered over the call surface. It works in a voice-only call too, where there's no camera at all. You hear their voice, you read their words. The interesting design constraint was who pays for what. Captions are switched on by the side that reads them. That means your microphone audio may be streamed to the speech provider because your partner turned captions on — so the app tells you that. That caption audio goes from the speaker's browser straight to the provider — our backend only mints a short-lived session to