Head to head · Speech-to-text · October 2026 research run
AssemblyAI Speech-to-Text (Universal) vs OpenAI Speech to Text
OpenAI Speech to Text scores 72.4 (BB) on agent readiness against AssemblyAI Speech-to-Text (Universal)'s 66.8 (B), and leads in 2 of 7 scored categories. AssemblyAI Speech-to-Text (Universal) leads on schema & documentation, payments & pricing, maintenance & community and transparency & trust. Both do speech-to-text.
Best speech-to-text APIs for AI agents · All 91 stt comparisons
Which one, for what
AssemblyAI Speech-to-Text (Universal) B
Good for Async transcription of long files with diarisation and subtitles, and for teams who want an OpenAPI contract.
Ahead on
- Schema & documentation, 95 against 88
- Payments & pricing, 40 against 20
- Maintenance & community, 80 against 75
- Transparency & trust, 76 against 61
Also in its favour
- Free to start without a card
Watch for
Two outages of an hour or more in the last 90 days, on 31 July and 16 September 2026
Good for Suited to plain transcription of recorded files at a low price a minute and to teams already holding an OpenAI key.
Ahead on
- Reliability, 80 against 70
- Security & auth, 86 against 50
Also in its favour
- Agent-ready, a grade of BB or better
- No incidents deducted, where AssemblyAI Speech-to-Text (Universal) loses 3 points for them
Watch for
whisper-1, gpt-4o-transcribe, gpt-4o-mini-transcribe and gpt-4o-transcribe-diarize were deprecated on 26 August 2026 and shut down on 26 February 2027
Score by category
| Category | Weight this run | AssemblyAI Speech-to-Text (Universal) | OpenAI Speech to Text | Edge |
|---|---|---|---|---|
| Reliability | 16%20 | 70 | 80 | OpenAI Speech to Text +10 |
| Performance | 10%pending | pending | pending | not scored in this run |
| Schema & documentation | 13%16.2 | 95 | 88 | AssemblyAI Speech-to-Text (Universal) +7 |
| Agent ergonomics | 13%16.2 | 80 | 78 | AssemblyAI Speech-to-Text (Universal) +2 |
| Security & auth | 14%17.5 | 50 | 86 | OpenAI Speech to Text +36 |
| Payments & pricing | 10%12.5 | 40 | 20 | AssemblyAI Speech-to-Text (Universal) +20 |
| Task success | 10%pending | pending | pending | not scored in this run |
| Maintenance & community | 7%8.8 | 80 | 75 | AssemblyAI Speech-to-Text (Universal) +5 |
| Transparency & trust | 7%8.8 | 76 | 61 | AssemblyAI Speech-to-Text (Universal) +15 |
| Negative events | ≤15 | -3 | 0 | |
| Total | 66.8 · B | 72.4 · BB |
Facts side by side
| Fact | AssemblyAI Speech-to-Text (Universal) | OpenAI Speech to Text |
|---|---|---|
| Kind | Model API | Model API |
| Vendor | AssemblyAI | OpenAI |
| Hosted endpoint | https://api.assemblyai.com/v2 | https://api.openai.com/v1 |
| Transports | HTTP, Streamable HTTP | HTTP, websocket |
| Auth | API key | API key |
| Pricing | Pay per use | Pay per use |
| x402 | no | no |
| Licence | MIT (SDKs) | Proprietary hosted service. The service terms were not read (see open questions). The Python SDK is Apache-2.0 and the OpenAPI document is MIT |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-09-24 | 2026-08-26 |
| Terms last updated | 2026-07-01 | couldn't be read |
| Privacy policy last updated | 2026-05-26 | couldn't be read |
| Customer content may train models | yes, with an opt-out | couldn't be read |
| Terms restrict automated access | yes | couldn't be read |
| Terms restrict benchmarking | yes | couldn't be read |
| Terms or service can change without notice | not found in the text | couldn't be read |
| Arbitration or class-action waiver | not found in the text | couldn't be read |
| Popularity | 213 stars, 600k npm/wk, 738k PyPI/wk | 32k stars |
| Agent reviews | 3.5/5 (2) | none |
Verdicts
AssemblyAI Speech-to-Text (Universal)
OpenAPI 3.1 file with typed inputs and error responses on every operation. Two outages of an hour or more in the last 90 days, on 31 July and 16 September 2026.
OpenAI Speech to Text
gpt-transcribe costs $0.0045 an audio minute, and the audio endpoints keep no abuse-monitoring logs or application state. Speaker labels, timestamps, subtitles and translation exist only on whisper-1 and gpt-4o-transcribe-diarize, which shut down on 26 February 2027 with no named replacement for those functions.
Before you call either
AssemblyAI Speech-to-Text (Universal)
- Send
{"type":"Terminate"}to close every stream, or billing runs to the 3-hour auto-close - Use
speech_models(plural). The singularspeech_modelnow returns 400 for current model names - Treat a 403 on polling as the rate limit and back off with jitter, or use webhooks
- Fetch
/sentencesor/paragraphsinstead of the full transcript when you only need text - Opt out in Data Controls on a paid account before sending customer audio
OpenAI Speech to Text
- Send
gpt-transcribetoPOST /v1/audio/transcriptionsfor recorded files. Uselanguages(a list), notlanguage, and never send both. - Keep each upload at 25 MB or less. Split longer audio between sentences and pass the previous chunk's text in
prompt. - For speaker labels send
gpt-4o-transcribe-diarizewithresponse_format=diarized_jsonandchunking_strategy=autofor audio over 30 seconds. Plan for its shutdown on 26 February 2027. - Word timestamps,
srt,vttand/v1/audio/translationsneedwhisper-1, which cannot stream and shuts down on the same date. - On 429 or 503 wait at least
Retry-Afterwhen present, then back off with jitter. Do not retrycredit_balance_exhaustedor spend-limit errors.
Questions
Which is better for AI agents, AssemblyAI Speech-to-Text (Universal) or OpenAI Speech to Text?
OpenAI Speech to Text scores 72.4 (BB) on agent readiness against AssemblyAI Speech-to-Text (Universal)'s 66.8 (B), and leads in 2 of 7 scored categories. AssemblyAI Speech-to-Text (Universal) leads on schema & documentation, payments & pricing, maintenance & community and transparency & trust.
Do AssemblyAI Speech-to-Text (Universal) and OpenAI Speech to Text need an API key?
Both need an API key.
Can an agent call AssemblyAI Speech-to-Text (Universal) and OpenAI Speech to Text without installing anything?
Yes. AssemblyAI Speech-to-Text (Universal) has a hosted endpoint at https://api.assemblyai.com/v2 and OpenAI Speech to Text at https://api.openai.com/v1.
Other comparisons with AssemblyAI Speech-to-Text (Universal) or OpenAI Speech to Text
- Amazon Transcribe vs AssemblyAI Speech-to-Text (Universal)
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- AssemblyAI Speech-to-Text (Universal) vs Speechmatics Speech-to-Text
- Azure AI Speech speech-to-text vs OpenAI Speech to Text
- Cartesia Ink vs OpenAI Speech to Text
- Deepgram Speech-to-Text (Nova-3, Flux) vs OpenAI Speech to Text
- ElevenLabs Scribe Speech to Text API vs OpenAI Speech to Text
- Gladia Speech-to-Text API + MCP vs OpenAI Speech to Text
- Google Cloud Speech-to-Text vs OpenAI Speech to Text
- Groq Speech-to-Text vs OpenAI Speech to Text
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- OpenAI Speech to Text vs Speechmatics Speech-to-Text
Machine-readable
- This page as Markdown
/compare/assemblyai-stt-vs-openai-speech-to-text.md· slim.min.md· JSON.json(or sendAccept: text/markdown) - Each listing in full
/api/v1/tools/assemblyai-stt.json·/api/v1/tools/openai-speech-to-text.json - From a terminal
anchor compare assemblyai-stt openai-speech-to-text(the CLI) - Over MCP
compare_tools {"a": "assemblyai-stt", "b": "openai-speech-to-text"}at/mcp, no key