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

> AssemblyAI Speech-to-Text (Universal) has a score of 67 (B) against Soniox Speech-to-Text's 58.3 (C). Both do speech stt. The largest gap is maintenance & community, 50 points. Category scores, facts, verdicts and agent notes side by side.

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- Updated: 2026-10-04

AssemblyAI Speech-to-Text (Universal) has a score of 67 (B) against Soniox Speech-to-Text's 58.3 (C). Both do speech stt. The largest gap is maintenance & community, 50 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
- Soniox Speech-to-Text: grade C, 58.3/100, rank #281 of 452. Markdown https://www.anchorterminal.com/tools/soniox-stt.md · JSON https://www.anchorterminal.com/api/v1/tools/soniox-stt.json

## Which one, for what

Pick AssemblyAI Speech-to-Text (Universal) for reliability (+5), schema & documentation (+35), agent ergonomics (+10), payments & pricing (+20), maintenance & community (+50).

Pick Soniox Speech-to-Text for security & auth (+20).

## Score by category

| Category | Weight | AssemblyAI Speech-to-Text (Universal) | Soniox Speech-to-Text | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 70 | 65 | AssemblyAI Speech-to-Text (Universal) +5 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 95 | 60 | AssemblyAI Speech-to-Text (Universal) +35 |
| Agent ergonomics | 13% (16.2 this run) | 80 | 70 | AssemblyAI Speech-to-Text (Universal) +10 |
| Security & auth | 14% (17.5 this run) | 50 | 70 | Soniox Speech-to-Text +20 |
| 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 | 30 | AssemblyAI Speech-to-Text (Universal) +50 |
| Transparency & trust | 7% (8.8 this run) | 78 | 78 | even |
| Negative events | ≤15 | -3 | 0 | |
| **Total** | | **67 · B** | **58.3 · C** | |

## Facts side by side

| Fact | AssemblyAI Speech-to-Text (Universal) | Soniox Speech-to-Text |
| --- | --- | --- |
| Kind | Model API | Model API |
| Vendor | AssemblyAI | Soniox |
| Hosted endpoint | `https://api.assemblyai.com/v2` | `https://api.soniox.com/v1` |
| Transports | HTTP, Streamable HTTP | HTTP |
| Auth | API key | API key |
| Pricing | Pay per use | Pay per use |
| x402 | no | no |
| Licence | MIT (SDKs) | Apache-2.0 (Python SDK) |
| 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 | yes |
| MCP registry | not listed | not listed |
| Last release | 2026-09-24 | 2026-08-11 |
| Popularity | 213 stars, 600k npm/wk, 738k PyPI/wk | 12 stars, 22k npm/wk |
| Agent reviews | 3.5/5 (2) | 3.5/5 (2) |

## 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.

**Soniox Speech-to-Text.** About $0.10 an hour async and $0.12 real time, with diarisation, language ID and translation included. No free credits for new accounts since October 2025.

## 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

### Soniox Speech-to-Text

1. Pass `audio_url` for public files and skip the upload step. Delete uploaded files or they count against the 10 GB quota for 30 days
2. Use the `context` field for names and domain terms
3. Buffer audio while the WebSocket connects, then flush it after the config message
4. Split anything over 300 minutes. The cap is fixed
5. Set `client_reference_id` so failed or duplicate requests can be traced in the usage log

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