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Top Voice AI companies are building with Assembly.
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Latest Release
Universal 3.5 Pro
Our new flagship speech-to-text model handles real-world audio the way it actually happens. Available for real-time and pre-recorded audio.
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Stream audio over a WebSocket and get formatted, immutable transcripts back with sub-300ms latency—accurate enough for production voice agents. Open a connection and start transcribing in a few lines of Python or JavaScript.
Hey, thanks for calling—can I grab your account number?
Sure, it's 4471-208-93—let me know if you need the zip too.
Got it, pulling that up right now.
Universal Streaming returns formatted, immutable transcripts fast enough to drive live voice agents and agent-assist.
Native turn detection, speaker labels, and keyterm prompting handle the hard parts of streaming audio out of the box.
Stream English plus Spanish, German, French, Italian, and Portuguese, with native code-switching mid-utterance.
36%
improvement in close rate
“The new Universal-3.5 Pro speech model from AssemblyAI is best so far in terms of accuracy, latency, and language switching.”
80%
increase in customer satisfaction
“Assembly has saved us countless hours managing models, and provided exceptional accuracy.”
36%
improvement in close rate
“The new Universal-3.5 Pro speech model from AssemblyAI is best so far in terms of accuracy, latency, and language switching.”
80%
increase in customer satisfaction
“Assembly has saved us countless hours managing models, and provided exceptional accuracy.”
Grab your API key and connect to the streaming WebSocket with the Python or JavaScript SDK—no infrastructure to stand up. Handle partial and finalized turns with a single event handler and start building.
Start building freeNo credit card required
Streaming word error rate measures real-time transcription accuracy against a human reference—the core signal for anything that acts on live audio.
Streaming word error rate on English audio.
*Lower is better*Source: AssemblyAI published benchmarks — assemblyai.com/benchmarks.
