# AssemblyAI Speech-to-Text (Universal) vs Inworld STT (slim)

> AssemblyAI Speech-to-Text scores 66.8 (B) to Inworld STT's 54.7 (C) for speech-to-text. Prices, MCP, x402, uptime and agent notes side by side.

- Full: https://www.anchorterminal.com/compare/assemblyai-stt-vs-inworld-stt.md (~5,850 tokens) · this version ~3,430 tokens · JSON https://www.anchorterminal.com/compare/assemblyai-stt-vs-inworld-stt.json · canonical https://www.anchorterminal.com/compare/assemblyai-stt-vs-inworld-stt
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · MCP: https://www.anchorterminal.com/mcp · Updated: 2026-11-07
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AssemblyAI Speech-to-Text (Universal) scores 66.8 (B) on agent readiness against Inworld STT's 54.7 (C), and leads in 5 of 7 scored categories. Inworld STT leads on security & auth. Both do speech-to-text.

- AssemblyAI Speech-to-Text (Universal): B 66.8, rank #355 of 1510 · https://www.anchorterminal.com/tools/assemblyai-stt.min.md
- Inworld STT: C 54.7, rank #900 of 1510 · https://www.anchorterminal.com/tools/inworld-stt.min.md
- AssemblyAI Speech-to-Text (Universal), good for Async transcription of long files with diarisation and subtitles, and for teams who want an OpenAPI contract. Ahead on Reliability, 85 against 60; Schema & documentation, 95 against 54; Agent ergonomics, 80 against 56; Maintenance & community, 79 against 41; Transparency & trust, 77 against 60. Also A hosted endpoint, with nothing to install.
- Inworld STT, good for Low-cost live transcription for voice agents, with speaker traits. Ahead on Security & auth, 63 against 50. Also No incidents deducted, where AssemblyAI Speech-to-Text (Universal) loses 6 points for them.

| Category | AssemblyAI Speech-to-Text (Universal) | Inworld STT |
| --- | --- | --- |
| Reliability (16%) | 85 | 60 |
| Performance (10%) | pending | pending |
| Schema & documentation (13%) | 95 | 54 |
| Agent ergonomics (13%) | 80 | 56 |
| Security & auth (14%) | 50 | 63 |
| Payments & pricing (10%) | 40 | 40 |
| Task success (10%) | pending | pending |
| Maintenance & community (7%) | 79 | 41 |
| Transparency & trust (7%) | 77 | 60 |

| Fact (where they differ) | AssemblyAI Speech-to-Text (Universal) | Inworld STT |
| --- | --- | --- |
| Vendor | AssemblyAI | Inworld AI |
| Hosted endpoint | `https://api.assemblyai.com/v2` | no (local only) |
| Transports | HTTP, Streamable HTTP | HTTP, websocket |
| Price for speech-to-text | not published | $0.0017 per minute of audio |
| Licence | MIT (SDKs) | none |
| Tools exposed | none | 0 |
| Last release | 2026-10-19 | 2026-10-29 |
| Terms last updated | 2026-07-01 | 2025-06-11 |
| Privacy policy last updated | 2026-05-26 | 2026-01-18 |
| Customer content may train models | yes, with an opt-out | not found in the text |
| Terms restrict automated access | yes | not found in the text |
| Terms restrict benchmarking | yes | not found in the text |
| Popularity | 213 stars, 600k npm/wk, 738k PyPI/wk | none |
| Agent reviews | 3.5/5 (2) | none |

Why the edge:
- Schema & documentation, AssemblyAI Speech-to-Text (Universal) +41: AssemblyAI Speech-to-Text (Universal) 95 (OpenAPI 3.1 at /docs/openapi.yaml covering upload, transcript, subtitles, sentences, paragraphs, word search and redacted audio (25). llms.txt at /docs/llms.txt (10). Operation descriptions state purpose, and the model pages say which model to pick for which languages, though not when to avoid an endpoint (15). Request schemas use enums and required fields, with `audio_url` the only required input (15). 400, 401, 404, 429, 500, 503 and 504 responses defined on every operation, plus code samples in the docs (15). Versioned `/v2` paths and a dated public changelog (15).); 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.)
- Maintenance & community, AssemblyAI Speech-to-Text (Universal) +38: AssemblyAI Speech-to-Text (Universal) 79 (Read as a model, for deprecation notice and support rather than release counts and issue replies, on the lines deepgram-stt, gladia-stt and speechmatics-stt use in this run. Changelog entries for speech-to-text on 6, 7 and 16 October 2026 (silence trimming for English multichannel audio on 16 October), and Python SDK 1.6.5 on 19 October with typed Speech Understanding config for transcripts (30). Far more than three dated entries since 3 August, and the SDKs tagged Python 1.5.2 to 1.8.2 and Node 4.40.0 to 4.42.0 in the period (10 of 10). No deprecation policy, but removals carry dates. Legacy Summarization and Auto Chapters were announced on 6 October for 20 October, and the async default model change on 11 July for 7 August, rescheduled on 1 August to 2 September with a changed migration. The 10 July `speech_model` change took effect the day it was announced (5 of 10). Public changelog and a support address (10 of 15). The Python SDK had 8 open issues on 1 October, the newest from December 2025 and the oldest from March 2024, per the 1 October check, not re-read on 1 November, since GitHub's pages answered 403 (4 of 10). Official SDKs current, Python 1.8.2 on 23 October and Node 4.42.0 on 26 October (15). Both SDK repositories carry test and lint workflows, results not seen (5 of 10). 30 + 10 + 5 + 10 + 4 + 15 + 5 = 79.); 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.)
- Reliability, AssemblyAI Speech-to-Text (Universal) +25: AssemblyAI Speech-to-Text (Universal) 85 (Statuspage at status.assemblyai.com with component history, read from history.atom on 1 November (20). Fourteen incidents from 3 August to 1 November 2026, every one partial, read as this run reads partial incidents (one endpoint, one region, one model or some requests) and as deepgram-stt and speechmatics-stt are read. The longest are an outage of the US async endpoint on 16 September from an AWS service issue (about half of US async jobs failed for 75 minutes, per the 1 October check, with the EU endpoint unaffected), rejected Universal-3.6 Pro Realtime sessions on the US endpoint for two hours on 6 October, and slower EU async processing with some failures from 08:20 to 10:45 UTC on 5 October. On 28 October a change to temporary tokens failed some Real-time sessions with 502 until it was rolled back. The 31 July us-east streaming fault left the window on 30 October. Minor only (20). Limits published with numbers, 5 or 200+ parallel jobs, 20,000 HTTP requests per 5 minutes, 5 or 100+ new streams a minute, per the 1 October check (15). Overload handling is partly documented. Jobs queue rather than fail, the docs advise jittered polling and resubmitting after a server error, and incident notes say failed requests can be safely resubmitted, but the HTTP limit answers 403 rather than 429 and no Retry-After is documented (10). A 99.9% uptime SLA is stated in the docs FAQ, with credits under the terms of service (10). Async, streaming and Sync APIs are GA (10). 20 + 20 + 15 + 10 + 10 + 10 = 85.); 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.)
- Agent ergonomics, AssemblyAI Speech-to-Text (Universal) +24: AssemblyAI Speech-to-Text (Universal) 80 (API reading of the checklist. Responses can be sized by fetching sentences, paragraphs, SRT or VTT with `chars_per_caption`, or word search, instead of the full word array, though there's no field selection (20). `GET /v2/transcript` pages with `limit`, `before_id` and `after_id` and filters by status and date (20). Errors come back as an `error` string on the transcript and as documented streaming close codes such as 1008, readable but not always typed (15). No idempotency key, and a resubmitted job is a new billed job. The retry guide covers server errors only (10). One required parameter and official SDKs in Python and TypeScript among others (15).); 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.)
- Transparency & trust, AssemblyAI Speech-to-Text (Universal) +17: AssemblyAI Speech-to-Text (Universal) 77 (Closed service with clear terms (15). Retention periods, the training opt-out FAQ and the security overview agree with each other, but the retention page says training happens only as the contract permits while the FAQ says free users can't opt out, which a reader has to reconcile (25). Deprecations are dated in the changelog, but on 10 July 2026 the singular `speech_model` parameter started rejecting current model names the same day it was announced (10). Subprocessor list at /legal/subprocessors and US and EU endpoints (20).); 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.)
- Security & auth, Inworld STT +13: AssemblyAI Speech-to-Text (Universal) 50 (Model reading of the checklist, with training and retention in place of least-privilege and injection lines. Plain revocable API keys per account, with dashboard roles that since 1 September 2026 stop Reader users managing keys, and single-use browser tokens that last at most 600 seconds. Those tokens go in the WebSocket URL, which we don't deduct for at that lifetime (20). Training is on by default. Paid accounts opt out in the dashboard, free accounts can't (5). Async audio is deleted after 24 to 48 hours and transcripts after 30 days, with a TTL from 1 hour and a delete endpoint. Streaming is zero-retention only once opted out (10). Per-transcript history through the list endpoint and dashboard, no audit log of key or admin actions found (10). SOC 2 Type 2 with a Vanta trust centre (5). No security.txt, disclosure policy, bug bounty or public advisories found (0). The security.txt reading of 30 September came from /.well-known, which www.assemblyai.com's robots.txt disallows, so it is struck and security.txt is unchecked. That leaves the programme line at 5 on the SOC 2 claim and the trust centre. 20 + 5 + 10 + 10 + 5 = 50.); 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.)

| Task | AssemblyAI Speech-to-Text (Universal) | Inworld STT |
| --- | --- | --- |
| Transcribe a one-hour meeting | $0.15 to $0.45 | $0.10 to $0.15 |