AssemblyAI

AssemblyAI builds speech-to-text and speech understanding APIs for developers creating products around voice data. Its tools turn recordings and live conversations into transcripts, identify speakers, and support tasks such as summarization, content moderation and personal-information redaction. Customers build meeting assistants, conversation intelligence and audio-video applications on its infrastructure; in December 2023, AssemblyAI named Fireflies.ai, Veed and CallRail among its customers. Founded by Dylan Fox, the company focuses on the speech infrastructure those teams integrate into their own products.

A defining part of its work is making transcription sensitive to the application’s context. Released in February 2026, Universal-3 Pro accepts plain-language instructions about names, terminology, topics and formatting before processing audio. Developers can also prompt for speaker labels, non-speech audio tags and either verbatim or cleaned-up speech. This gives teams a way to guide what the transcript captures while the model still has access to acoustic information, rather than relying entirely on corrections to finished text.

AssemblyAI also offers the Voice Agent API, launched in April 2026, which combines speech understanding, language-model reasoning and voice generation through a single WebSocket connection. It handles conversational turn detection using acoustic and semantic signals to distinguish a pause from a completed thought, and supports interruptions and custom tool calls. Teams can use that integrated pipeline or keep AssemblyAI’s streaming speech-to-text as a component in a stack built with LiveKit or Pipecat.