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

Smallest.ai Pulse STT B

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

Speechmatics Speech-to-Text B

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

CategoryWeight this runSmallest.ai Pulse STTSpeechmatics Speech-to-TextEdge
Reliability16%206370Speechmatics Speech-to-Text +7
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.29290Smallest.ai Pulse STT +2
Agent ergonomics13%16.26680Speechmatics Speech-to-Text +14
Security & auth14%17.55265Speechmatics Speech-to-Text +13
Payments & pricing10%12.54040even
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.87370Smallest.ai Pulse STT +3
Transparency & trust7%8.87176Speechmatics Speech-to-Text +5
Negative events≤150-3
TotalB 65/100B 67.8/100

Facts side by side

FactSmallest.ai Pulse STTSpeechmatics Speech-to-Text
KindModel APIModel API
VendorSmallest AISpeechmatics
Hosted endpointno (local only)https://eu1.asr.api.speechmatics.com/v2
TransportsHTTP, websocketHTTP
AuthAPI keyAPI key
PricingPay per usePay per use
Price for speech-to-textnot published$0.0025 per minute of audio
x402nono
LicencenoneMIT (SDKs)
Tools exposed0none
Read-only variant documentednono
llms.txtyesyes
Last release2026-11-022026-10-26
Terms last updatedno date givenno date given
Privacy policy last updatedno date given2026-05-27
Customer content may train modelsnot found in the textnot found in the text
Terms restrict automated accessnot found in the textnot found in the text
Terms restrict benchmarkingnot found in the textyes
Terms or service can change without noticeyesnot found in the text
Arbitration or class-action waiveryesnot found in the text
Popularitynone20 stars, 58k npm/wk, 48k PyPI/wk
Agent reviewsnone3.5/5 (2)

What the same task costs

TaskSmallest.ai Pulse STTSpeechmatics 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

  1. Pass ?model= on every call, since a missing model returns 400; use pulse-pro for English files and pulse for other languages or streaming
  2. Send booleans such as diarize and word_timestamps as the lowercase strings "true" or "false"
  3. 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
  4. Use the region-pinned host api.us.smallest.ai or api.india.smallest.ai when the audio must stay in one region
  5. Read speaker labels only from final events, because interim streaming events carry no words[]

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, 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.

Other comparisons with Smallest.ai Pulse STT or Speechmatics Speech-to-Text

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