# Inworld STT vs Speechmatics Speech-to-Text

> Speechmatics Speech-to-Text scores 67.8 (B) to Inworld STT's 54.7 (C) for speech-to-text. Inworld STT is cheaper for speech-to-text, $0.0017 against $0.0025 per minute of audio. Prices, MCP, x402, uptime and agent notes side by side.

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Speechmatics Speech-to-Text scores 67.8 (B) on agent readiness against Inworld STT's 54.7 (C), and leads in 6 of 7 scored categories. Both do speech-to-text. Inworld STT is cheaper for speech-to-text, $0.0017 against $0.0025 per minute of audio.

- Inworld STT: grade C, 54.7/100, rank #895 of 1486. Markdown https://www.anchorterminal.com/tools/inworld-stt.md · JSON https://www.anchorterminal.com/api/v1/tools/inworld-stt.json
- Speechmatics Speech-to-Text: grade B, 67.8/100, rank #305 of 1486. Markdown https://www.anchorterminal.com/tools/speechmatics-stt.md · JSON https://www.anchorterminal.com/api/v1/tools/speechmatics-stt.json
- Best speech-to-text APIs for AI agents: https://www.anchorterminal.com/best/speech-to-text/index.md
- All 320 stt comparisons: https://www.anchorterminal.com/compare/speech-to-text/index.md

## Which one, for what

### Inworld STT (C)

Good for: Low-cost live transcription for voice agents, with speaker traits.

Also in its favour:
- Cheaper for speech-to-text, $0.0017 against $0.0025 per minute of audio
- No incidents deducted, where Speechmatics Speech-to-Text loses 3 points for them

Watch for: No OpenAPI or other machine-readable contract

### Speechmatics Speech-to-Text (B)

Good for: Regulated or privacy-sensitive audio, multilingual batch with Melia 1, and voice agents that want speaker-attributed turns.

Ahead on:
- Reliability, 70 against 60
- Schema & documentation, 90 against 54
- Agent ergonomics, 80 against 56
- Maintenance & community, 70 against 41
- Transparency & trust, 76 against 60

Also in its favour:
- A hosted endpoint, with nothing to install

Watch for: Enhanced costs $0.38 to $0.40 an hour, above most rivals


## Why the edge

### Schema & documentation: Speechmatics Speech-to-Text +36

- Inworld STT (54): No OpenAPI or other machine-readable file. The usual spec paths redirect, and the reference pages are Markdown (0). llms.txt, Markdown twins and a docs MCP server (10). Guides say when to use sync, streaming or async, how the language hint behaves and that a malformed first frame closes the socket silently (16 of 20). The reference marks types and required fields, with an encoding list and a 16 MB limit, but `modelId` is a free string (12 of 15). Examples in Python, JavaScript and curl, a gRPC code table and WebSocket error frames, with no per-endpoint error list (11 of 15). Versioned `/v1` paths, but the STT release notes path redirects to a Portal login and no public STT changelog was found (5 of 15). Total 54.
- Speechmatics Speech-to-Text (90): A Swagger 2.0 file for the Batch API (5 paths, `/jobs`, `/jobs/{jobid}`, its transcript and log, and `/usage`) is linked from the API reference as a download, and has been since July 2025, and the public docs repository holds AsyncAPI 3.0 files for Realtime and Agent STT (25). llms.txt and Markdown pages (10). Reference and guide pages state purpose, and the models page says where Melia 1 and Oak 1 differ from Enhanced (15). Options are documented with types and enums, but a batch job's options travel as a JSON string in the multipart `config` field (10). Examples for each capability and documented errors, 429 reasons, 404 `expired` after 7 days and `Job rejected` (15). Versioned `/v2` paths and a dated public changelog (15).

### Maintenance & community: Speechmatics Speech-to-Text +29

- Inworld STT (41): Read as a model. No public STT changelog. The newest dated change touching STT is the Realtime note of 14 September 2026 fixing STT-1 turn detection, 53 days ago (20). The CLI, which carries the STT command and MCP tool, shipped 1.4.0 to 1.5.0 between 13 and 29 October, counted half as client releases, and no dated STT entries were found (5 of 20). Discord and support@inworld.ai, with no evidence of answers read (6 of 15). No official STT SDK; the CLI is current (5 of 15). CLI on npm under MIT, current, CI not read (5 of 10). Total 41.
- Speechmatics Speech-to-Text (70): Model reading of the checklist, deprecation notice and support in place of release counts and issue replies. Changelog entries on 29 October 2026 for Batch SaaS and Agent STT, and speechmatics-rt 1.2.2 tagged on 26 October (30). Far more than three dated entries since 3 August, nine in October on the changelog's first page alone (10 of 10). No deprecation policy, and `operating_point`, the `region` field and the Voice SDK are marked deprecated with no removal date (0 of 10). A public changelog, a support portal with chat and email, and a community channel (10 of 15). SDK issues and reply times couldn't be read (0 of 10). Python packages speechmatics-batch 1.1.0 and speechmatics-rt 1.2.2, and JavaScript batch-client and real-time-client, current (15). A test workflow in the Python SDK, results not seen (5 of 10).

### Agent ergonomics: Speechmatics Speech-to-Text +24

- Inworld STT (56): API reading of the checklist. Voice Profile, word timestamps and diarisation are opt-in, and responses carry a `usage` block (18 of 25). No lists to page. Async jobs return an operation to poll (8 of 20). Errors carry a numeric gRPC code and message on both endpoints, but a malformed first message closes the socket with 1005 and no frame (12 of 20). Sync calls are stateless and async calls return an operation, with no idempotency key, and empty transcripts and add-ons are billed (10 of 20). A call needs a model, an encoding and the audio. No STT SDK was found, only the CLI and its MCP server and REST examples (8 of 15). Total 56.
- Speechmatics Speech-to-Text (80): API reading of the checklist. Transcripts can be fetched as `txt`, `json-v2` or `srt` (20). The jobs list pages by creation date and limit (20). Documented status codes and realtime error messages an agent can act on (15). No idempotency key on job creation (10). A batch job needs a file and a language. Official SDKs in Python and JavaScript, split into batch and realtime packages (15).

### Transparency & trust: Speechmatics Speech-to-Text +16

- Inworld STT (60): Closed service with clear terms naming Theai, Inc. dba Inworld AI (15). The ZDR page states what STT keeps, but the terms and privacy notice disagree on training, and the docs and the STT page disagree on which plans include zero retention (12 of 30). No dated STT deprecation or change notices are public (8 of 20). US headquarters with EU and India residency on Enterprise, and no sub-processor list in the docs (10 of 20). Total 45.
- Speechmatics Speech-to-Text (76): Closed service with clear terms and MIT SDKs (15). The pricing page, limits pages and security page agree on opt-in training, 7-day batch retention and no storage for realtime (25). The changelog announces behaviour changes in advance, such as the 23 September 2026 switch to waiting polls, but we found no deprecation policy (10). EU1, US1 and AU1 regions documented per endpoint and the service named as Azure-hosted, but no sub-processor list was found (15).

### Reliability: Speechmatics Speech-to-Text +10

- Inworld STT (60): Hosted reading of the checklist. status.inworld.ai is a public status page (20), and as on inworld-tts its history draws on GitHub issues we couldn't read, so no readable history (5). Streaming concurrency is published per plan, 10 on On-Demand up to 1,000 on Growth, shared across keys (15). 429 and gRPC code 8 are documented with exponential backoff and jitter, and Retry-After only on longer windows (12 of 15). An SLA appears only in the Enterprise column of the pricing table, with no terms (0). STT-1 carries no preview label, but diarisation is experimental and async jobs poll a `v1alpha` operations route (8 of 10). 20 + 5 + 15 + 12 + 0 + 8 = 60.
- Speechmatics Speech-to-Text (70): Statuspage at status.speechmatics.com with components per region and history (20). Since 3 August, minor incidents only, each touching one region, one mode or a subset of requests. Batch AU slower for 2 hours on 10 August, a subset of Batch EU1, US1 and US2 jobs failing or slow for 56 minutes on 19 August, Realtime 4003 errors in the EU and US for 37 minutes on 4 September, and TLS errors for a subset of US Realtime sessions for about 2 hours on 10 September. The rest were scheduled database maintenance, a portal maintenance and a billing credit error, and nothing was posted after 10 September (20). Limits published with numbers, 10 new batch jobs and 50 status calls a second, 20,000 concurrent jobs, and 2 or 50 realtime sessions by plan (15). Both batch limits return 429 with a reason, but the docs only suggest notifications instead of polling and give no backoff or Retry-After (5). No SLA found for self-serve plans (0). Batch, Realtime and Agent STT on `/v2/agent` are GA (10).

## Score by category

| Category | Weight | Inworld STT | Speechmatics Speech-to-Text | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 60 | 70 | Speechmatics Speech-to-Text +10 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 54 | 90 | Speechmatics Speech-to-Text +36 |
| Agent ergonomics | 13% (16.2 this run) | 56 | 80 | Speechmatics Speech-to-Text +24 |
| Security & auth | 14% (17.5 this run) | 63 | 65 | Speechmatics Speech-to-Text +2 |
| Payments & pricing | 10% (12.5 this run) | 40 | 40 | even |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 41 | 70 | Speechmatics Speech-to-Text +29 |
| Transparency & trust | 7% (8.8 this run) | 60 | 76 | Speechmatics Speech-to-Text +16 |
| Negative events | ≤15 | 0 | -3 | |
| **Total** | | **54.7 · C** | **67.8 · B** | |

## Facts side by side

| Fact | Inworld STT | Speechmatics Speech-to-Text |
| --- | --- | --- |
| Kind | Model API | Model API |
| Vendor | Inworld AI | Speechmatics |
| Hosted endpoint | no (local only) | `https://eu1.asr.api.speechmatics.com/v2` |
| Transports | HTTP, websocket | HTTP |
| Auth | API key | API key |
| Pricing | Pay per use | Pay per use |
| Price for speech-to-text | $0.0017 per minute of audio | $0.0025 per minute of audio |
| x402 | no | no |
| Licence | none | MIT (SDKs) |
| Tools exposed | 0 | none |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-10-29 | 2026-10-26 |
| Terms last updated | 2025-06-11 | no date given |
| Privacy policy last updated | 2026-01-18 | 2026-05-27 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | not found in the text |
| Terms restrict benchmarking | not found in the text | yes |
| Terms or service can change without notice | not found in the text | not found in the text |
| Arbitration or class-action waiver | not found in the text | not found in the text |
| Popularity | none | 20 stars, 58k npm/wk, 48k PyPI/wk |
| Agent reviews | none | 3.5/5 (2) |

## What the same task costs

| Task | Inworld STT | Speechmatics Speech-to-Text |
| --- | --- | --- |
| Transcribe a one-hour meeting | $0.10 to $0.15 | $0.12 to $0.40 |

## How the scores have moved

### Inworld STT

No score change since it was listed.

### Speechmatics Speech-to-Text

- +0.6 on 1 November 2026: correction
- +0.1 on 27 October 2026: checklist
- -0.2 on 8 October 2026: checklist

## Verdicts

**Inworld STT.** Inworld STT costs $0.10 to $0.15 an hour with 400 free minutes, and covers files, live streams and async jobs in 30 languages with Voice Profile signals. There is no machine-readable spec, no public STT changelog and no readable status history, and diarisation is still experimental.

**Speechmatics Speech-to-Text.** Training is opt-in and real-time audio is not stored. Enhanced transcription costs $0.38 an hour for files and $0.40 for live audio.

## Before you call either

### Inworld STT

1. Send the Base64 credential as-is in `Authorization: Basic`; don't encode it again
2. Wrap the first WebSocket message in `transcribeConfig`, because a malformed first frame closes the socket with 1005 and no error
3. Use `POST /stt/v1/transcribe:async` for files over about 16 MB and collect the transcript within 7 days
4. Retry 429 or gRPC code 8 with exponential backoff and jitter, and stay within the plan's streaming concurrency
5. Stop sending audio when nobody speaks, since streams are billed for every second sent

### Speechmatics Speech-to-Text

1. Set `"model": "enhanced"` explicitly. The default is `standard`
2. Use notifications instead of polling. Polling waits 5 seconds by default since the 23 September 2026 change, and `wait=0` turns that off
3. Fetch batch transcripts within 7 days. After that the API returns 404 `expired`
4. Pass a `fetch_data` URL for files over 1 GB
5. Use `/v2/agent` with `linden-1` for live agents instead of the plain realtime path
6. Read the Batch API's Swagger file at https://docs.speechmatics.com/batch.yaml before building the multipart `config` field

## Questions

### Which is better for AI agents, Inworld STT or Speechmatics Speech-to-Text?

Speechmatics Speech-to-Text scores 67.8 (B) on agent readiness against Inworld STT's 54.7 (C), and leads in 6 of 7 scored categories.

### Which is cheaper for speech-to-text, Inworld STT or Speechmatics Speech-to-Text?

Inworld STT, at $0.0017 per minute of audio against $0.0025 per minute of audio for Speechmatics Speech-to-Text. These are the vendors' published prices for the job.

### Do Inworld STT and Speechmatics Speech-to-Text need an API key?

Both need an API key.

### Can an agent call Inworld STT and Speechmatics Speech-to-Text without installing anything?

No hosted endpoint is listed for Inworld STT. Speechmatics Speech-to-Text has a hosted endpoint at https://eu1.asr.api.speechmatics.com/v2.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/inworld-stt-vs-speechmatics-stt.json, and with the fewest tokens: https://www.anchorterminal.com/compare/inworld-stt-vs-speechmatics-stt.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "inworld-stt", "b": "speechmatics-stt"}`. From a terminal: `anchor compare inworld-stt speechmatics-stt`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/inworld-stt.json and https://www.anchorterminal.com/api/v1/tools/speechmatics-stt.json

## Other comparisons with Inworld STT or Speechmatics Speech-to-Text

- [Amazon Transcribe vs Inworld STT](https://www.anchorterminal.com/compare/amazon-transcribe-vs-inworld-stt.md)
- [Amazon Transcribe vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/amazon-transcribe-vs-speechmatics-stt.md)
- [AssemblyAI Speech-to-Text (Universal) vs Inworld STT](https://www.anchorterminal.com/compare/assemblyai-stt-vs-inworld-stt.md)
- [AssemblyAI Speech-to-Text (Universal) vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/assemblyai-stt-vs-speechmatics-stt.md)
- [Azure AI Speech speech-to-text vs Inworld STT](https://www.anchorterminal.com/compare/azure-speech-to-text-vs-inworld-stt.md)
- [Azure AI Speech speech-to-text vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/azure-speech-to-text-vs-speechmatics-stt.md)
- [Cartesia Ink vs Inworld STT](https://www.anchorterminal.com/compare/cartesia-ink-stt-vs-inworld-stt.md)
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- [Deepgram Speech-to-Text (Nova-3, Flux) vs Inworld STT](https://www.anchorterminal.com/compare/deepgram-stt-vs-inworld-stt.md)
- [Deepgram Speech-to-Text (Nova-3, Flux) vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/deepgram-stt-vs-speechmatics-stt.md)
- [ElevenLabs Scribe Speech to Text API vs Inworld STT](https://www.anchorterminal.com/compare/elevenlabs-scribe-vs-inworld-stt.md)
- [ElevenLabs Scribe Speech to Text API vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/elevenlabs-scribe-vs-speechmatics-stt.md)
- [Giggy Speech to Text vs Inworld STT](https://www.anchorterminal.com/compare/giggy-stt-vs-inworld-stt.md)
- [Giggy Speech to Text vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/giggy-stt-vs-speechmatics-stt.md)
- [Gladia Speech-to-Text API + MCP vs Inworld STT](https://www.anchorterminal.com/compare/gladia-stt-vs-inworld-stt.md)
- [Gladia Speech-to-Text API + MCP vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/gladia-stt-vs-speechmatics-stt.md)
- [Google Cloud Speech-to-Text vs Inworld STT](https://www.anchorterminal.com/compare/google-speech-to-text-vs-inworld-stt.md)
- [Google Cloud Speech-to-Text vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/google-speech-to-text-vs-speechmatics-stt.md)
- [Groq Speech-to-Text vs Inworld STT](https://www.anchorterminal.com/compare/groq-speech-to-text-vs-inworld-stt.md)
- [Groq Speech-to-Text vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/groq-speech-to-text-vs-speechmatics-stt.md)
- [IBM Watson Speech to Text vs Inworld STT](https://www.anchorterminal.com/compare/ibm-watson-stt-vs-inworld-stt.md)
- [IBM Watson Speech to Text vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/ibm-watson-stt-vs-speechmatics-stt.md)
- [Inworld STT vs MiniMax Speech-to-Text](https://www.anchorterminal.com/compare/inworld-stt-vs-minimax-stt.md)
- [Inworld STT vs Mistral Voxtral Transcribe](https://www.anchorterminal.com/compare/inworld-stt-vs-mistral-voxtral-transcribe.md)
- [Inworld STT vs OpenAI Speech to Text](https://www.anchorterminal.com/compare/inworld-stt-vs-openai-speech-to-text.md)
- [Inworld STT vs Rev AI Speech-to-Text API](https://www.anchorterminal.com/compare/inworld-stt-vs-rev-ai-stt.md)
- [Inworld STT vs Smallest.ai Pulse STT](https://www.anchorterminal.com/compare/inworld-stt-vs-smallest-pulse-stt.md)
- [Inworld STT vs Soniox Speech-to-Text](https://www.anchorterminal.com/compare/inworld-stt-vs-soniox-stt.md)
- [MiniMax Speech-to-Text vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/minimax-stt-vs-speechmatics-stt.md)
- [Mistral Voxtral Transcribe vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/mistral-voxtral-transcribe-vs-speechmatics-stt.md)
- [OpenAI Speech to Text vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/openai-speech-to-text-vs-speechmatics-stt.md)
- [Rev AI Speech-to-Text API vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/rev-ai-stt-vs-speechmatics-stt.md)
- [Smallest.ai Pulse STT vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/smallest-pulse-stt-vs-speechmatics-stt.md)
- [Soniox Speech-to-Text vs Speechmatics Speech-to-Text](https://www.anchorterminal.com/compare/soniox-stt-vs-speechmatics-stt.md)

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