Head to head · Speech-to-text · October 2026 research run
Smallest.ai Pulse STT vs Speechmatics Speech-to-Text
Speechmatics Speech-to-Text scores 67.8 (B) on agent readiness against Smallest.ai Pulse STT's 65 (B), and leads in 4 of 7 scored categories. Both do speech-to-text.
Best speech-to-text APIs for AI agents · All 320 stt comparisons
Which one, for what
Best for Low-cost transcription for voice agents and call analytics, with Indic coverage and turn detection.
Also in its favour
- No incidents deducted, where Speechmatics Speech-to-Text loses 3 points for them
Watch for
Health checks on the shared API failed in all three regions on 9, 10, 13, 14 and 15 September 2026, the longest about 64 minutes
Best for Regulated or privacy-sensitive audio, multilingual batch with Melia 1, and voice agents that want speaker-attributed turns.
Ahead on
- Reliability, 70 against 63
- Agent ergonomics, 80 against 66
- Security & auth, 65 against 52
- Transparency & trust, 76 against 71
Also in its favour
- A hosted endpoint, with nothing to install
- Free to start without a card
Watch for
Enhanced costs $0.38 to $0.40 an hour, above most rivals
Why the edge
Each category where one leads by five points or more, with the reason behind each side's score from its assessment. The numbers are in the table below; this is what they stand for.
Agent ergonomics Speechmatics Speech-to-Text +14
Smallest.ai Pulse STT 66
API reading of the checklist. Word timestamps, utterances, diarisation, emotion and gender are each opt-in, so the default response is the transcript with metadata (18 of 25). There are no list endpoints for transcriptions to page. Output controls are the opt-in fields and finalisation settings on the socket (10 of 20). Errors carry a status and a machine-readable code or error_code (LANGUAGE_NOT_SUPPORTED_BY_MODEL, AudioTooLong and others) with fixes, but the body comes in two shapes, message or error (15 of 20). Batch calls are synchronous with no idempotency key, and whether a retried file is billed again isn't stated (10 of 20). A file call needs only the model and audio. Official Python and Node SDKs exist, though the Node SDK was last published in May 2025 (13 of 15). Total 66.
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).
Security & auth Speechmatics Speech-to-Text +13
Smallest.ai Pulse STT 52
Model reading of the checklist, with training and retention in place of the least-privilege and injection lines. Plain sk_ keys per organisation, shown once, revoked at once and deletable, with one key per environment advised. The docs say a key grants full account access, and no scope is offered. Short-lived access tokens (wat_, 30 to 900 seconds) cover only inference routes and can't mint tokens (22 of 30). The error reference documents the key as a ?token= query parameter for browser WebSockets, and the token guide passes access tokens as ?api_key= on the STT socket, so 10 off (12 of 30). The terms (21 October 2026) say Smallest won't use user content or input to train or improve its services. The privacy policy (18 September 2026) lists improving the services with machine learning as a use of usage data and doesn't address uploaded audio or text either way (15 of 20). Zero data retention and the x-expire-content header are Enterprise only, or a $1,000 a month HIPAA add-on on pay as you go. Other plans keep content readable in logs and the dashboard, with no retention period published (5 of 15). Usage is tracked per key, request rows sit in a dashboard log viewer, and every response carries x-request-id. No audit log of key actions was found (10 of 15). security.txt is valid to 31 December 2026 and the site footer claims SOC 2, GDPR and HIPAA compliance, while the pricing page lists SOC 2 compliance only on Enterprise. No bug bounty, disclosure policy or public advisories found (10 of 20). Total 52.
Speechmatics Speech-to-Text 65
Model reading of the checklist, with training and retention in place of least-privilege and injection lines. API keys as bearer tokens, with a separate management token for key administration (20). Browser and realtime clients pass temporary keys as ?jwt= on the WebSocket URL, with a lifetime the caller sets from 60 to 86,400 seconds, so we deduct half (minus 5). Training is opt-in only, and opting in buys a 33 per cent discount (20). Realtime audio isn't stored, batch data is deleted after 7 days or on request (15). A usage reporting service exists, but we found no per-request audit log (10). ISO/IEC 27001:2022 and SOC 2 Type II with a SafeBase trust centre. No security.txt (404 on 1 November), disclosure policy, bug bounty or public advisories found (5).
Reliability Speechmatics Speech-to-Text +7
Smallest.ai Pulse STT 63
BetterStack status page at status.smallest.ai with components for the Global, India and USA APIs (one health check covers the Agents and Models APIs), docs, the app and Electron, and per-component history (20). In the 90 days from 8 August the health checks on the shared API failed in all three regions on 9, 10, 13, 14 and 15 September (about 8, 21, 33, 17 and 64 minutes of flapping), in the Global and India regions on 11 and 17 September (12 minutes each), and in the USA region alone on 1, 3, 5, 12, 21 and 30 September (6 to 62 minutes) and 6 October (12 minutes). Outages in every region at once are read as wide errors, so several majors (0). Standard plan limits published per model, 100 concurrent streaming sessions and 25 batch requests a minute, and the pricing page also says 100 concurrent STT streams (15). 429 is documented with exponential backoff from 500 ms to 30 s and Retry-After when present, and batch calls are synchronous with optional webhooks (15). An infrastructure SLA of 99.99 per cent is named for Enterprise only, with no terms published, and the terms disclaim any availability commitment (5 of 10). Pulse, Pulse 2.0 and Pulse Pro carry no preview label, but eleven language codes are marked Beta (8 of 10). 20 + 0 + 15 + 15 + 5 + 8 = 63.
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).
Transparency & trust Speechmatics Speech-to-Text +5
Smallest.ai Pulse STT 71
Closed service with clear terms naming Smallest Inc. under California law (15). The ZDR page is specific about what each mode keeps, but the terms' no-training clause and the privacy policy's machine-learning use of usage data sit side by side, the privacy policy gives no retention periods, and the policy doesn't mention the DPA a footer link points to (15 of 30). A deprecations page gives statuses, dates and migration targets, deprecated routes return a Deprecation: true header, and the 30 September changelog removed 14 European codes from the batch enum with a migration to multi-eu. The terms still let Smallest change or discontinue services at any time without notice (15 of 20). Two regions named (Mumbai and Oregon) with region-pinned hosts, and only Google Analytics and Fullstory named among third parties, with no sub-processor list found (10 of 20). Total 55.
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).
Score by category
| Category | Weight this run | Smallest.ai Pulse STT | Speechmatics Speech-to-Text | Edge |
|---|---|---|---|---|
| Reliability | 16%20 | 63 | 70 | Speechmatics Speech-to-Text +7 |
| Performance | 10%pending | pending | pending | not scored in this run |
| Schema & documentation | 13%16.2 | 92 | 90 | Smallest.ai Pulse STT +2 |
| Agent ergonomics | 13%16.2 | 66 | 80 | Speechmatics Speech-to-Text +14 |
| Security & auth | 14%17.5 | 52 | 65 | Speechmatics Speech-to-Text +13 |
| Payments & pricing | 10%12.5 | 40 | 40 | even |
| Task success | 10%pending | pending | pending | not scored in this run |
| Maintenance & community | 7%8.8 | 73 | 70 | Smallest.ai Pulse STT +3 |
| Transparency & trust | 7%8.8 | 71 | 76 | Speechmatics Speech-to-Text +5 |
| Negative events | ≤15 | 0 | -3 | |
| Total | B 65/100 | B 67.8/100 |
Facts side by side
| Fact | Smallest.ai Pulse STT | Speechmatics Speech-to-Text |
|---|---|---|
| Kind | Model API | Model API |
| Vendor | Smallest 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 | not published | $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 | 2026-11-02 | 2026-10-26 |
| Terms last updated | no date given | no date given |
| Privacy policy last updated | no date given | 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 | yes | not found in the text |
| Arbitration or class-action waiver | yes | 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 | Smallest.ai Pulse STT | Speechmatics Speech-to-Text |
|---|---|---|
| Transcribe a one-hour meeting60 minutes of recorded audio | $0.18 to $0.30 | $0.12 to $0.40 |
Estimated from each listing's published prices, the same tasks as on the price index. Plans, minimums and free allowances aren't counted.
How the scores have moved
Verdicts
Smallest.ai Pulse STT
Pulse covers files and live audio on one endpoint, with OpenAPI and AsyncAPI files, a dated changelog and public per-minute prices from $0.003. The shared API's health checks failed in every region on five days in September, keys carry no scopes and can travel in a URL, and zero retention is Enterprise only.
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
Smallest.ai Pulse STT
- Pass
?model=on every call, since a missing model returns 400; usepulse-profor English files andpulsefor other languages or streaming - Send booleans such as
diarizeandword_timestampsas the lowercase strings "true" or "false" - Retry 429 with backoff from 500 ms up to 30 s and honour Retry-After; keep within 25 batch requests a minute on the Standard plan
- Use the region-pinned host api.us.smallest.ai or api.india.smallest.ai when the audio must stay in one region
- Read speaker labels only from final events, because interim streaming events carry no
words[]
Speechmatics Speech-to-Text
- Set
"model": "enhanced"explicitly. The default isstandard - Use notifications instead of polling. Polling waits 5 seconds by default since the 23 September 2026 change, and
wait=0turns that off - Fetch batch transcripts within 7 days. After that the API returns 404
expired - Pass a
fetch_dataURL for files over 1 GB - Use
/v2/agentwithlinden-1for live agents instead of the plain realtime path - Read the Batch API's Swagger file at https://docs.speechmatics.com/batch.yaml before building the multipart
configfield
Questions
Which is better for AI agents, Smallest.ai Pulse STT or Speechmatics Speech-to-Text?
Speechmatics Speech-to-Text scores 67.8 (B) on agent readiness against Smallest.ai Pulse STT's 65 (B), and leads in 4 of 7 scored categories.
Do Smallest.ai Pulse STT and Speechmatics Speech-to-Text need an API key?
Both need an API key.
Can an agent call Smallest.ai Pulse STT and Speechmatics Speech-to-Text without installing anything?
No hosted endpoint is listed for Smallest.ai Pulse STT. Speechmatics Speech-to-Text has a hosted endpoint at https://eu1.asr.api.speechmatics.com/v2.
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Machine-readable
- This page as Markdown
/compare/smallest-pulse-stt-vs-speechmatics-stt.md· slim.min.md· JSON.json(or sendAccept: text/markdown) - Each listing in full
/api/v1/tools/smallest-pulse-stt.json·/api/v1/tools/speechmatics-stt.json - From a terminal
anchor compare smallest-pulse-stt speechmatics-stt(the CLI) - Over MCP
compare_tools {"a": "smallest-pulse-stt", "b": "speechmatics-stt"}at/mcp, no key