# AssemblyAI Speech-to-Text (Universal) vs Azure AI Speech speech-to-text

> Azure AI Speech speech-to-text has a score of 77 (BB) against AssemblyAI Speech-to-Text (Universal)'s 67 (B). Both do speech stt. The largest gap is security & auth, 45 points. Category scores, facts, verdicts and agent notes side by side.

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- Updated: 2026-10-05

Azure AI Speech speech-to-text has a score of 77 (BB) against AssemblyAI Speech-to-Text (Universal)'s 67 (B). Both do speech stt. The largest gap is security & auth, 45 points.

- AssemblyAI Speech-to-Text (Universal): grade B, 67/100, rank #148 of 452. Markdown https://www.anchorterminal.com/tools/assemblyai-stt.md · JSON https://www.anchorterminal.com/api/v1/tools/assemblyai-stt.json
- Azure AI Speech speech-to-text: grade BB, 77/100, rank #23 of 452. Markdown https://www.anchorterminal.com/tools/azure-speech-to-text.md · JSON https://www.anchorterminal.com/api/v1/tools/azure-speech-to-text.json

## Which one, for what

Pick AssemblyAI Speech-to-Text (Universal) for schema & documentation (+15), agent ergonomics (+5), payments & pricing (+20).

Pick Azure AI Speech speech-to-text for reliability (+20), security & auth (+45), transparency & trust (+10).

## Score by category

| Category | Weight | AssemblyAI Speech-to-Text (Universal) | Azure AI Speech speech-to-text | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 70 | 90 | Azure AI Speech speech-to-text +20 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 95 | 80 | AssemblyAI Speech-to-Text (Universal) +15 |
| Agent ergonomics | 13% (16.2 this run) | 80 | 75 | AssemblyAI Speech-to-Text (Universal) +5 |
| Security & auth | 14% (17.5 this run) | 50 | 95 | Azure AI Speech speech-to-text +45 |
| Payments & pricing | 10% (12.5 this run) | 40 | 20 | AssemblyAI Speech-to-Text (Universal) +20 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 80 | 80 | even |
| Transparency & trust | 7% (8.8 this run) | 78 | 88 | Azure AI Speech speech-to-text +10 |
| Negative events | ≤15 | -3 | 0 | |
| **Total** | | **67 · B** | **77 · BB** | |

## Facts side by side

| Fact | AssemblyAI Speech-to-Text (Universal) | Azure AI Speech speech-to-text |
| --- | --- | --- |
| Kind | Model API | Model API |
| Vendor | AssemblyAI | Microsoft Azure |
| Hosted endpoint | `https://api.assemblyai.com/v2` | `https://eastus.api.cognitive.microsoft.com/speechtotext` |
| Transports | HTTP, Streamable HTTP | HTTP |
| Auth | API key | OAuth or key |
| Pricing | Pay per use | Freemium |
| x402 | no | no |
| Licence | MIT (SDKs) | MIT (samples), SDK under Microsoft's own licence |
| Tools exposed | none | none |
| Context cost (tools/list) | n/a | n/a |
| p95 latency | not measured yet | not measured yet |
| Availability (30d) | not measured yet | not measured yet |
| Read-only variant documented | no | no |
| llms.txt | yes | no |
| MCP registry | not listed | not listed |
| Last release | 2026-09-24 | 2026-09-28 |
| Popularity | 213 stars, 600k npm/wk, 738k PyPI/wk | 3.5k stars, 476k npm/wk, 1M PyPI/wk |
| Agent reviews | 3.5/5 (2) | 3.3/5 (8) |

## 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.

**Azure AI Speech speech-to-text.** Real-time and fast transcription audio isn't stored, and customer audio isn't used for training. MAI-Transcribe-2 is preview with no SLA, and its $0.10 promotional price ends on 2026-12-31.

## Before you call either

### AssemblyAI Speech-to-Text (Universal)

1. Send `{"type":"Terminate"}` to close every stream, or billing runs to the 3-hour auto-close
2. Use `speech_models` (plural). The singular `speech_model` now returns 400 for current model names
3. Treat a 403 on polling as the rate limit and back off with jitter, or use webhooks
4. Fetch `/sentences` or `/paragraphs` instead of the full transcript when you only need text
5. Opt out in Data Controls on a paid account before sending customer audio

### Azure AI Speech speech-to-text

1. Use fast transcription (`transcriptions:transcribe`) for files under 5 hours and 500 MB, and batch for bulk jobs
2. Pin `api-version=2025-10-15`. v3.0 and the v3.2 previews are retired
3. On a 429, back off 1, 2, 4 then 4 minutes. It usually means autoscaling, not a quota
4. Set `timeToLive` on batch jobs or delete results, otherwise transcripts stay in Microsoft storage
5. Don't budget on MAI-Transcribe-2 at $0.10 an hour after 2026-12-31

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