Speech to Text APIs
Transcription APIs here mostly start with a free trial and handle both pre-recorded and streaming audio. AssemblyAI adds speaker labels and subtitles, Speechmatics offers diarization in batch or real time, and Gladia and Rev AI sell add-ons such as translation, summaries and sentiment. Deepgram pairs transcription with text-to-speech and voice agents, and Audexum runs on a freemium plan. Free AI APIs →
| API | Pricing | Auth | Format | Free tier | Status |
|---|---|---|---|---|---|
AssemblyAISpeech-to-text for files and live audio in 99 languages, with speaker labels, subtitles and an LLM gateway. AI & Machine Learning › Speech | Free trial | API key | JSON | — | Live |
AudexumText-to-speech in 43 voices and 32 languages, plus speech-to-text transcription in 100+ languages. AI & Machine Learning › Speech | Freemium | API key | JSON | — | Live |
DeepgramSpeech-to-text and text-to-speech transcription with streaming and pre-recorded audio, plus voice agents. AI & Machine Learning › Speech | Free trial | API key | JSON | — | Live |
GladiaAsync and real-time speech-to-text API with translation, summarization, and sentiment add-ons. AI & Machine Learning › Speech | Free trial | API key | JSON | — | Live |
Rev AIAsync and streaming transcription with captions, translation, summaries, sentiment and topic extraction. AI & Machine Learning › Speech | Free trial | API key | JSON | — | Live |
SpeechmaticsBatch and real-time transcription in 55+ languages with diarization, plus low-latency English TTS. AI & Machine Learning › Speech | Free trial | API key | JSON | — | Live |
AssemblyAIFree trialLive
Speech-to-text for files and live audio in 99 languages, with speaker labels, subtitles and an LLM gateway.
API key · JSON
—
no machine-readable spec
AudexumFreemiumLive
Text-to-speech in 43 voices and 32 languages, plus speech-to-text transcription in 100+ languages.
API key · JSON
—
llms.txt
DeepgramFree trialLive
Speech-to-text and text-to-speech transcription with streaming and pre-recorded audio, plus voice agents.
API key · JSON
—
no machine-readable spec
GladiaFree trialLive
Async and real-time speech-to-text API with translation, summarization, and sentiment add-ons.
API key · JSON
—
llms.txt
Rev AIFree trialLive
Async and streaming transcription with captions, translation, summaries, sentiment and topic extraction.
API key · JSON
—
OpenAPI spec
SpeechmaticsFree trialLive
Batch and real-time transcription in 55+ languages with diarization, plus low-latency English TTS.
API key · JSON
—
no machine-readable spec
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Choosing a Speech to Text API
Is there a free Speech to Text API?
Yes. Audexum has a free tier alongside paid plans. See all free AI APIs.
Which Speech to Text APIs work without an API key?
All of them need a key or account. Audexum gives one out free when you sign up.
Can I use Speech to Text APIs in a commercial project?
AssemblyAI, Deepgram, Speechmatics and Gladia permit commercial use. Audexum and Rev AI restrict it, for example to non-commercial or attributed use, so read the terms first.
Which Speech to Text APIs work with AI agents?
Rev AI publishes an OpenAPI spec for generating clients and tools.
Broader: Speech APIs · AI & Machine Learning APIs
More in Speech: Text to Speech APIs · Voice Cloning APIs