AssemblyAI
AssemblyAI offers speech-to-text and voice AI APIs, including its Universal speech models, streaming transcription, speech understanding and a voice agent API.
About this tool
AssemblyAI is an API company focused on voice. Developers send audio and receive transcripts with formatting, word-level timestamps, language detection, speaker information and optional custom spelling or key-term prompting. Its Universal family of models covers both batch and real-time use, with the multilingual Universal-2 supporting 99 languages and the newer Universal-3.5 Pro aimed at top accuracy in a smaller set of languages.
Beyond transcription, AssemblyAI sells speech understanding features, a dictation API that returns clean ready-to-send text, a synchronous API for short clips, and a voice agent offering billed per hour. Pricing is pay-as-you-go with no minimum commitment after a free start, and the company says it processes millions of hours of audio daily.
What you can do
Universal speech models
Accurate transcription across many languages, with formatting, timestamps and key-term prompting.
Streaming and sync APIs
Real-time transcription for live audio and a sync endpoint that returns short clips in a single call.
Dictation API
Turns spoken input into polished text, removing filler words and resolving self-corrections.
Voice agent API
A per-hour offering for building conversational voice agents, with bring-your-own telephony.
Who is it for?
- A meeting-notes app transcribes and diarises customer calls at scale.
- A developer adds voice dictation to a note-taking app.
- A contact centre analyses recorded calls for topics and sentiment.
Before you choose
Costs depend on the model and add-on features you enable, so model the per-hour total for your expected volume.
Language support differs between models; check that your languages are covered by the model you choose.
Frequently asked questions
Is AssemblyAI free?
You can start for free, then pay as you go per hour of audio. There are no minimum commitments according to AssemblyAI.
How many languages does AssemblyAI support?
It depends on the model. Universal-2 is listed with 99 languages, while Universal-3.5 Pro focuses on 18 languages with higher accuracy.
Can AssemblyAI transcribe in real time?
Yes. It offers streaming transcription for live audio in addition to batch and synchronous APIs.
Check the official website for current features, pricing, and terms.
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