# Inworld STT vs Rev AI Speech-to-Text API

> Rev AI Speech-to-Text and Inworld STT score within a point of each other for speech-to-text, 55.5 and 54.7 out of 100. Prices, MCP, x402, uptime and agent notes side by side.

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- Updated: 2026-11-07

Rev AI Speech-to-Text API and Inworld STT score within a point of each other on agent readiness, 55.5 (C) and 54.7 (C). Inworld STT leads on security & auth and payments & pricing. Both do speech-to-text.

- 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
- Rev AI Speech-to-Text API: grade C, 55.5/100, rank #862 of 1486. Markdown https://www.anchorterminal.com/tools/rev-ai-stt.md · JSON https://www.anchorterminal.com/api/v1/tools/rev-ai-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.

Ahead on:
- Security & auth, 63 against 40
- Payments & pricing, 40 against 20

Also in its favour:
- Free to start without a card

Watch for: No OpenAPI or other machine-readable contract

### Rev AI Speech-to-Text API (C)

Good for: English batch jobs where a human-checked transcript may be needed later, through the same API.

Ahead on:
- Reliability, 75 against 60
- Schema & documentation, 80 against 54
- Transparency & trust, 69 against 60

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

Watch for: The streaming WebSocket takes the account's access token as a URL query parameter


## Why the edge

### Schema & documentation: Rev AI Speech-to-Text API +26

- 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.
- Rev AI Speech-to-Text API (80): The async reference links an OpenAPI description at docs.rev.ai/_bundle/api/asynchronous/reference.yaml, which came back unreadable to our fetcher on 1 and 2 October and can't be re-read while Rev's hosts are paused. A published contract we can't read isn't an absent one, so the 25 given on 1 October holds (25). llms.txt (10). Endpoint descriptions state purpose, and the docs explain when to choose the machine, foreign-language or human transcriber (15). Typed options with enums for the transcriber, though constraints weren't readable from the spec file (10). The reference excerpt read shows no error responses for `POST /jobs` (5). Versioned `/speechtotext/v1` paths and a dated changelog (15). Docs per the 1 and 2 October checks, not re-read on 4 November. 25+10+15+10+5+15 = 80.

### Security & auth: Inworld STT +23

- Inworld STT (63): Model reading of the checklist, with training and retention in place of the least-privilege and injection lines. Workspace API keys sent as Basic credentials, deleted to revoke, with separate keys per environment advised. The CLI mints read-only keys unless `--write` is given, but write toggles cover only the Voice and Router APIs, so no key is limited to one product. Browsers use short-lived tokens minted server side, via the `bearer_` WebSocket subprotocol, not the URL (25 of 30). The Terms (11 June 2025) say Inworld won't train generally available models on customers' non-public Materials, except feedback and flagged content, while the Privacy Notice (18 January 2026) lists training AI models among its uses, per the inworld-tts check of 4 November (12 of 20). Zero data retention keeps STT audio and transcripts in memory and out of logs, included on Developer ($300 a month) and above per the docs, while the STT page says Enterprise or a Growth add-on. Async results and audio go after 7 days, and no default period is given for logs (8 of 15). Usage is attributed per key and a Performance page shows errors and throttling (8 of 15). SOC 2 Type II and HIPAA claimed and a vulnerability report form, with no security.txt or bug bounty, per the 4 November reading (10 of 20). Total 63.
- Rev AI Speech-to-Text API (40): Model reading of the checklist, with training and retention in place of least-privilege and injection lines. Bearer access tokens, generated and replaced from the account page, with no scopes found (20). The streaming WebSocket takes that long-lived token as an `access_token` query parameter, a documented secret in a URL (minus 10). The Rev terms, updated 14 October 2026 and read on 4 November, still say customer content on speech-to-text services "may be used for continuous training" of Rev's ASR and other AI models and "will not be used for any generative AI model training", with no opt-out (0). Jobs and media are deleted after 30 days, sooner with `delete_after_seconds`, an account setting or a delete call. Streaming retention isn't stated (10). Jobs are listed per account, no audit log found (10). Rev's security page names SOC 2 Type II and links a SOC 3 report, plus PCI, HIPAA on the enterprise tier and CJIS. No security.txt, disclosure policy or bug bounty found (10 of 20). Docs and security page per the 1 and 2 October checks. 10+0+10+10+10 = 40.

### Payments & pricing: Inworld STT +20

- Inworld STT (40): No x402, MPP or L402 (0). Per-hour prices for every plan published without a login (20). On-Demand includes up to 400 minutes of STT and lists no payment method, while async jobs need one (20). A person signs up in the Portal or through `inworld login` in a browser before a key exists (0). Total 40.
- Rev AI Speech-to-Text API (20): No x402, MPP or L402 (0). Per-hour and per-minute prices published without a login (20). Free credits worth 5 hours of Reverb, but whether sign-up needs a card wasn't confirmed (0). A person signs up in a browser (0). Pricing per the 2 October check, not re-read on 4 November (Rev hosts paused). 0+20+0+0 = 20.

### Reliability: Rev AI Speech-to-Text API +15

- 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.
- Rev AI Speech-to-Text API (75): Statuspage at status.rev.ai with component history (20), per the 1 October check, not re-read on 4 November, because the Rev terms (updated 14 October 2026) bar using any automated system to extract content from Rev's web sites, so every Rev host is paused for this run. The history feed read on 1 October showed no incident since 13 May 2026, and the page has posted eight incidents since September 2022. The window from 6 August is held at what that reading supports, with 2 October to 4 November unread (30). Limits published with numbers, 10,000 async submissions and 500 processing jobs per 10 minutes and 10 concurrent streams (15). No 429 handling, Retry-After or backoff guidance in the async reference, the get-started page or the changelog (0). No SLA found, and the pricing page names none (0). Async and streaming are GA (10). All per the 1 and 2 October checks. 20+30+15+0+0+10 = 75.

### Transparency & trust: Rev AI Speech-to-Text API +9

- 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.
- Rev AI Speech-to-Text API (69): Closed service under the Rev.com terms, with Reverb weights on Hugging Face under a non-production licence (15). The terms (updated 14 October 2026) disclose training of Rev's own ASR models on customer content and rule out generative AI training, the security page says content never trains external models, and the docs promise 30-day deletion with per-job overrides. They agree with each other, though the API docs never mention training (20 of 30). Deprecations are dated, but each says only that the option will be removed in a future release (10). EU deployment in Frankfurt documented, no sub-processor list found (10). Security page and docs per the 1 and 2 October checks. 15+20+10+10 = 55.

## Score by category

| Category | Weight | Inworld STT | Rev AI Speech-to-Text API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 60 | 75 | Rev AI Speech-to-Text API +15 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 54 | 80 | Rev AI Speech-to-Text API +26 |
| Agent ergonomics | 13% (16.2 this run) | 56 | 52 | Inworld STT +4 |
| Security & auth | 14% (17.5 this run) | 63 | 40 | Inworld STT +23 |
| Payments & pricing | 10% (12.5 this run) | 40 | 20 | Inworld STT +20 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 41 | 40 | Inworld STT +1 |
| Transparency & trust | 7% (8.8 this run) | 60 | 69 | Rev AI Speech-to-Text API +9 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **54.7 · C** | **55.5 · C** | |

## Facts side by side

| Fact | Inworld STT | Rev AI Speech-to-Text API |
| --- | --- | --- |
| Kind | Model API | Model API |
| Vendor | Inworld AI | Rev |
| Hosted endpoint | no (local only) | `https://api.rev.ai/speechtotext/v1` |
| Transports | HTTP, websocket | HTTP |
| Auth | API key | API key |
| Pricing | Pay per use | Freemium |
| Price for speech-to-text | $0.0017 per minute of audio | not published |
| 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 | 2024-11-27 |
| Terms last updated | 2025-06-11 | 2026-05-15 |
| Privacy policy last updated | 2026-01-18 | 2026-02-03 |
| Customer content may train models | not found in the text | yes |
| Terms restrict automated access | not found in the text | yes |
| Terms restrict benchmarking | not found in the text | not found in the text |
| 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 | 36 stars, 16k npm/wk, 130k PyPI/wk |
| Agent reviews | none | 2.5/5 (2) |

## What the same task costs

| Task | Inworld STT | Rev AI Speech-to-Text API |
| --- | --- | --- |
| Transcribe a one-hour meeting | $0.10 to $0.15 | $0.20 to $119 |

## How the scores have moved

### Inworld STT

No score change since it was listed.

### Rev AI Speech-to-Text API

- -2.4 on 4 November 2026: correction, checklist
- +0.1 on 28 October 2026: new evidence
- -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.

**Rev AI Speech-to-Text API.** Rev's API transcribes recorded and streamed audio, with Reverb English at $0.20 an hour and human transcription through the same job endpoint. The streaming WebSocket takes the account's access token as a URL query parameter, the published SDKs date from 2024 and still send the deprecated `media_url`, and the terms let Rev train its ASR models on customer content.

## 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

### Rev AI Speech-to-Text API

1. Keep streaming URLs out of logs. They carry `access_token`
2. Send `source_config: {"url": ...}`, not `media_url`, even though the published SDKs still use `media_url`
3. Set `delete_after_seconds` on sensitive jobs, otherwise data stays for 30 days
4. Use `notification_config` webhooks rather than polling job status
5. Don't build on `low_cost` or `fusion`. Both are deprecated

## Questions

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

Rev AI Speech-to-Text API and Inworld STT score within a point of each other on agent readiness, 55.5 (C) and 54.7 (C). Inworld STT leads on security & auth and payments & pricing.

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

Both need an API key.

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

No hosted endpoint is listed for Inworld STT. Rev AI Speech-to-Text API has a hosted endpoint at https://api.rev.ai/speechtotext/v1.


## For agents

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

## Other comparisons with Inworld STT or Rev AI Speech-to-Text API

- [Amazon Transcribe vs Inworld STT](https://www.anchorterminal.com/compare/amazon-transcribe-vs-inworld-stt.md)
- [Amazon Transcribe vs Rev AI Speech-to-Text API](https://www.anchorterminal.com/compare/amazon-transcribe-vs-rev-ai-stt.md)
- [AssemblyAI Speech-to-Text (Universal) vs Inworld STT](https://www.anchorterminal.com/compare/assemblyai-stt-vs-inworld-stt.md)
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