# Deepgram Text-to-Speech (Aura-2, Flux TTS) vs Smallest.ai Lightning TTS

> Deepgram Text-to-Speech scores 75.6 (BB) to Smallest.ai Lightning TTS's 64.4 (B) for text-to-speech. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/deepgram-tts-vs-smallest-lightning-tts
- Markdown: https://www.anchorterminal.com/compare/deepgram-tts-vs-smallest-lightning-tts.md (~5,600 tokens)
- Site index for agents: https://www.anchorterminal.com/llms.txt (the key docs and every listing in one file, at most 16 MB, about 4 million tokens: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- MCP: https://www.anchorterminal.com/mcp (the whole catalogue as tools, no key)
- DNS: dig +short TXT <slug>.grade.anchorterminal.com (the grade as a DNS TXT record, for a sandbox with no HTTP where names still resolve; also top., best.<category>. and <a>.vs.<b>. under the zone, and the same under grade.letme.dev)
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)
- Updated: 2026-11-07

Deepgram Text-to-Speech (Aura-2, Flux TTS) scores 75.6 (BB) on agent readiness against Smallest.ai Lightning TTS's 64.4 (B), and leads in 6 of 7 scored categories. Both do text-to-speech.

- Deepgram Text-to-Speech (Aura-2, Flux TTS): grade BB, 75.6/100, rank #58 of 1510. Markdown https://www.anchorterminal.com/tools/deepgram-tts.md · JSON https://www.anchorterminal.com/api/v1/tools/deepgram-tts.json
- Smallest.ai Lightning TTS: grade B, 64.4/100, rank #471 of 1510. Markdown https://www.anchorterminal.com/tools/smallest-lightning-tts.md · JSON https://www.anchorterminal.com/api/v1/tools/smallest-lightning-tts.json
- Best text-to-speech APIs for AI agents: https://www.anchorterminal.com/best/text-to-speech/index.md
- All 148 tts comparisons: https://www.anchorterminal.com/compare/text-to-speech/index.md

## Which one, for what

### Deepgram Text-to-Speech (Aura-2, Flux TTS) (BB)

Good for: English voice agents that need clean barge-in handling and an operator who wants a typed spec and request logs.

Ahead on:
- Reliability, 80 against 58
- Agent ergonomics, 82 against 72
- Security & auth, 72 against 52
- Maintenance & community, 73 against 68
- Transparency & trust, 78 against 70

Also in its favour:
- Agent-ready, a grade of BB or better
- A hosted endpoint, with nothing to install
- Runs on your own machine
- Free to start without a card

Watch for: Requests can be kept for training unless each one sets `mip_opt_out=true`

### Smallest.ai Lightning TTS (B)

Good for: Low-latency speech for voice agents, with English, Hindi code-switching and Indic voices.

Watch for: `lightning_v3.1`, the default model, retires on 30 November 2026 after a 2 November notice, and clones made on it stop working


## Why the edge

### Reliability: Deepgram Text-to-Speech (Aura-2, Flux TTS) +22

- Deepgram Text-to-Speech (Aura-2, Flux TTS) (80): Statuspage at status.deepgram.com with component history and an RSS feed (20). Ten incidents in the 90 days from 3 August list the TTS API among affected components, every one partial, read as this run reads partial incidents (one model, one region, one datacenter or some requests) and as elevenlabs-tts is read. Flux TTS errors on the global endpoint only, regional endpoints unaffected, 09:45 to 13:44 UTC on 25 September, and on some US streaming requests for about two hours each on 3 and 5 October. Batch Flux TTS 503s for 91 minutes on 14 October. 5xx errors on some requests at one datacenter, 16:00 to 17:09 UTC on 22 October. Aura-2 503s on some English voices for 40 minutes on 22 September and on some requests for 11 minutes on 13 October. Short bursts on 30 September, 8 October and 29 October. Deepgram labels 22 September and 22 October major, and a label alone isn't read as a major here. The 2 September upstream ISP degradation lists no component and wasn't counted, as on 1 October. The 1 October check read 25 September as one major (10). The AWS us-west-2 event of 24 July has left the window. Minor only (20). TTS concurrency published per plan and region, 15 REST and 45 streaming on pay as you go, and Flux TTS only 5 in the EU, Australia and India (15). Rate-limit breaches return 429 and the docs ask for exponential backoff (15). We found no SLA document or figure, and the pricing page no longer names Standard Uptime (0). Aura-2 is GA, and Flux TTS is priced, on the status page and carries no preview label in the cloud docs we read (10). 20 + 20 + 15 + 15 + 0 + 10 = 80.
- Smallest.ai Lightning TTS (58): 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). Limits are published with numbers but disagree. The limits page says one TTS request at a time per account with up to five sockets, the Lightning v3.1 Pro card says 10 concurrent and the pricing page says 15 streams and 100 requests a minute on pay as you go (8 of 15). 429 is documented with exponential backoff from 500 ms to 30 s and Retry-After when present, and the limits page tells clients to expect 429s at the concurrency ceiling (15). An infrastructure SLA of 99.99 per cent is named for Enterprise only, with no terms, and the terms disclaim any availability commitment (5 of 10). `lightning_v3.1_pro` is stable and only the dated checkpoint is preview (10). 20 + 0 + 8 + 15 + 5 + 10 = 58.

### Security & auth: Deepgram Text-to-Speech (Aura-2, Flux TTS) +20

- Deepgram Text-to-Speech (Aura-2, Flux TTS) (72): Model reading of the checklist, with training and retention in place of least-privilege and injection lines. Keys belong to a project, carry a role and scopes, and browser JWTs live 30 seconds (30). Requests fall under the Model Improvement Program, which covers TTS, unless each request sets `mip_opt_out=true` (10 of 20). Opted-out requests are kept only for processing, so zero retention is self-serve but not the default (10 of 15). Per-request logs through `GET /v1/projects/{project_id}/requests`, no audit log of key actions found (10 of 15). SOC 2 Type 1 and Type 2, HIPAA with a BAA on request and PCI listed on the compliance page. deepgram.com now serves a valid security.txt (Contact security@deepgram.com, Expires 30 September 2027), not found on 30 September. No disclosure policy or bug bounty found (12 of 20). 30 + 10 + 10 + 10 + 12 = 72.
- Smallest.ai Lightning TTS (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.

### Agent ergonomics: Deepgram Text-to-Speech (Aura-2, Flux TTS) +10

- Deepgram Text-to-Speech (Aura-2, Flux TTS) (82): API reading of the checklist. Encoding, container, sample rate and bit rate are all chosen per request, streaming returns PCM, mu-law or A-law and batch adds MP3, Opus, FLAC and AAC. Word timestamps on Flux only (20 of 25). Aura-2 REST caps a request at 2,000 characters and answers 413 above it, and the request history endpoint pages and filters by date, status and endpoint (20). Documented error codes, an `INPUT_MARKUP_STRIPPED` warning when SSML is dropped, and Flux's Interrupt event returns what was spoken and what wasn't (17 of 20). Backoff guidance for 429. No idempotency key, and we found nothing on billing for failed calls (10 of 20). `/v1/speak` needs only the text, and official SDKs ship in Python, JavaScript, Go, .NET and Java (15).
- Smallest.ai Lightning TTS (72): API reading of the checklist. Eight output formats, a choice of sample rate and word timestamps only when asked (22 of 25). Voices are listed per model and the docs say they filter by language and accent. Paging wasn't confirmed (14 of 20). Errors carry `error` and `message` fields with a shared status-code guide, without TTS-specific codes (14 of 20). Synthesis is stateless and `request_id` is echoed for correlation, but there is no idempotency key and billing of a retried request isn't stated (10 of 20). Two required fields, `text` and `voice_id`, but the default model retires on 30 November. Official Python and Node SDKs, with the Node SDK last published in May 2025 (12 of 15). Total 72.

### Transparency & trust: Deepgram Text-to-Speech (Aura-2, Flux TTS) +8

- Deepgram Text-to-Speech (Aura-2, Flux TTS) (78): Closed service with clear terms, SDKs MIT (15). The docs describe training by default under the Model Improvement Program and EU, Australian and Indian endpoints, while the privacy policy (last updated 26 October 2021, re-read on 1 November 2026) says data sits on US servers and doesn't mention the program (15 of 30). Breaking corrections are flagged in the changelog, but we found no deprecation policy (10 of 20). Sub-processor list and four regional endpoints (20).
- Smallest.ai Lightning TTS (70): 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 steps, and earlier models answer 410 with a pointer. The notice for the default `lightning_v3.1`, dated 2 November, gives 28 days before voices change and v3.1 clones stop working, and the terms let Smallest discontinue services without notice (12 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 52.

### Maintenance & community: Deepgram Text-to-Speech (Aura-2, Flux TTS) +5

- Deepgram Text-to-Speech (Aura-2, Flux TTS) (73): Read as a model. Changelog entries to 27 October 2026, the newest changing how callbacks, TTS callbacks included, are verified (30). 34 dated entries in the 90 days from 3 August (10). We found no deprecation policy and no TTS deprecation notices in the period (0 of 10). Public changelog and community support channels (10 of 15). The Python SDK had 27 open issues on 1 October, the newest from August 2026 with no maintainer reply visible, per the 1 October check, not re-read on 1 November (3 of 10). Official SDKs current in five languages, the Python SDK at 7.16.0 on 28 October (15). SDK CI not checked (5 of 10).
- Smallest.ai Lightning TTS (68): Read as a model. The newest Lightning changelog entry is dated 2 November 2026 (the v3.1 retirement notice), after a preview checkpoint on 29 October (30). Dated Lightning entries on 10, 23 and 28 August, 29 September, 14, 17 and 29 October and 2 November count, less 5 for churn, because the default model retires 28 days after its notice and clones made on it stop working (15 of 20). Public changelog, email support and a Discord server, with no evidence read of how they answer (10 of 15). The Python SDK `smallestai` 5.14.0 dates from 7 October, but the npm Node SDK has not been published since May 2025 (8 of 15). The Python SDK repository runs CI and release workflows, but has no licence file (5 of 10). Total 68.

## Score by category

| Category | Weight | Deepgram Text-to-Speech (Aura-2, Flux TTS) | Smallest.ai Lightning TTS | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 80 | 58 | Deepgram Text-to-Speech (Aura-2, Flux TTS) +22 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 95 | 92 | Deepgram Text-to-Speech (Aura-2, Flux TTS) +3 |
| Agent ergonomics | 13% (16.2 this run) | 82 | 72 | Deepgram Text-to-Speech (Aura-2, Flux TTS) +10 |
| Security & auth | 14% (17.5 this run) | 72 | 52 | Deepgram Text-to-Speech (Aura-2, Flux TTS) +20 |
| 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) | 73 | 68 | Deepgram Text-to-Speech (Aura-2, Flux TTS) +5 |
| Transparency & trust | 7% (8.8 this run) | 78 | 70 | Deepgram Text-to-Speech (Aura-2, Flux TTS) +8 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **75.6 · BB** | **64.4 · B** | |

## Facts side by side

| Fact | Deepgram Text-to-Speech (Aura-2, Flux TTS) | Smallest.ai Lightning TTS |
| --- | --- | --- |
| Kind | Model API | Model API |
| Vendor | Deepgram | Smallest AI |
| Hosted endpoint | `https://api.deepgram.com/v1` | no (local only) |
| Transports | HTTP, Streamable HTTP, stdio, SSE (legacy) | HTTP, websocket |
| Auth | API key | API key |
| Pricing | Pay per use | Pay per use |
| Price for text-to-speech | $45 per 1M characters | not published |
| x402 | no | no |
| Licence | MIT (SDKs) | none |
| Tools exposed | none | 0 |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-10-28 | 2026-11-02 |
| Terms last updated | 2026-08-06 | no date given |
| Privacy policy last updated | 2021-10-26 | no date given |
| Customer content may train models | yes, with an opt-out | not found in the text |
| Terms restrict automated access | not found in the text | not found in the text |
| Terms restrict benchmarking | yes | not found in the text |
| Terms or service can change without notice | yes | yes |
| Arbitration or class-action waiver | yes | yes |
| Popularity | 468 stars, 1.1M npm/wk, 805k PyPI/wk | none |
| Agent reviews | 3.5/5 (2) | none |

## What the same task costs

| Task | Deepgram Text-to-Speech (Aura-2, Flux TTS) | Smallest.ai Lightning TTS |
| --- | --- | --- |
| Narrate a 9,000-character script | $0.13 to $0.41 | $0.16 to $0.18 |

## How the scores have moved

### Deepgram Text-to-Speech (Aura-2, Flux TTS)

- +2.8 on 1 November 2026: security, correction
- +0.1 on 27 October 2026: checklist
- -0.3 on 8 October 2026: checklist

### Smallest.ai Lightning TTS

No score change since it was listed.

## Verdicts

**Deepgram Text-to-Speech (Aura-2, Flux TTS).** OpenAPI 3.1 and AsyncAPI files, llms.txt and Markdown pages. Requests can be kept for training unless each one sets `mip_opt_out=true`.

**Smallest.ai Lightning TTS.** Lightning streams speech over HTTP, SSE or WebSocket with OpenAPI and AsyncAPI files and public prices of $0.175 to $0.195 per 10,000 characters. The default model retires on 30 November with 28 days' notice, published concurrency limits disagree, and the shared API failed in every region on five days in September.

## Before you call either

### Deepgram Text-to-Speech (Aura-2, Flux TTS)

1. Set `mip_opt_out=true` on every request if the text mustn't be kept for training.
2. Split Aura-2 REST text under 2,000 characters or expect a 413.
3. Pass `model` on `/v2/speak`, where it's required.
4. Strip SSML before sending, since it's removed with an `INPUT_MARKUP_STRIPPED` warning.
5. Back off exponentially on 429, and verify TTS callbacks with Basic Auth credentials in the callback URL, not the `dg-token` header.

### Smallest.ai Lightning TTS

1. Always send `"model": "lightning_v3.1_pro"`, since requests with no model go to a model that retires on 30 November 2026
2. Pick voices from `GET /waves/v1/lightning-v3.1-pro/get_voices`, because the v3.1 and v3.1 Pro catalogues differ
3. Keep each request under 8,000 characters and split longer text
4. Treat 429 as the concurrency ceiling and retry with backoff from 500 ms to 30 s, honouring Retry-After
5. Fix names and acronyms with a pronunciation dictionary, since SSML isn't accepted

## Questions

### Which is better for AI agents, Deepgram Text-to-Speech (Aura-2, Flux TTS) or Smallest.ai Lightning TTS?

Deepgram Text-to-Speech (Aura-2, Flux TTS) scores 75.6 (BB) on agent readiness against Smallest.ai Lightning TTS's 64.4 (B), and leads in 6 of 7 scored categories.

### Do Deepgram Text-to-Speech (Aura-2, Flux TTS) and Smallest.ai Lightning TTS need an API key?

Both need an API key.

### Can an agent call Deepgram Text-to-Speech (Aura-2, Flux TTS) and Smallest.ai Lightning TTS without installing anything?

Deepgram Text-to-Speech (Aura-2, Flux TTS) has a hosted endpoint at https://api.deepgram.com/v1. No hosted endpoint is listed for Smallest.ai Lightning TTS.


## For agents

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

## Other comparisons with Deepgram Text-to-Speech (Aura-2, Flux TTS) or Smallest.ai Lightning TTS

- [Amazon Polly vs Deepgram Text-to-Speech (Aura-2, Flux TTS)](https://www.anchorterminal.com/compare/amazon-polly-vs-deepgram-tts.md)
- [Amazon Polly vs Smallest.ai Lightning TTS](https://www.anchorterminal.com/compare/amazon-polly-vs-smallest-lightning-tts.md)
- [Azure AI Speech text-to-speech vs Deepgram Text-to-Speech (Aura-2, Flux TTS)](https://www.anchorterminal.com/compare/azure-text-to-speech-vs-deepgram-tts.md)
- [Azure AI Speech text-to-speech vs Smallest.ai Lightning TTS](https://www.anchorterminal.com/compare/azure-text-to-speech-vs-smallest-lightning-tts.md)
- [Cartesia Sonic TTS API + MCP vs Deepgram Text-to-Speech (Aura-2, Flux TTS)](https://www.anchorterminal.com/compare/cartesia-tts-vs-deepgram-tts.md)
- [Cartesia Sonic TTS API + MCP vs Smallest.ai Lightning TTS](https://www.anchorterminal.com/compare/cartesia-tts-vs-smallest-lightning-tts.md)
- [Deepgram Text-to-Speech (Aura-2, Flux TTS) vs ElevenLabs Text to Speech API + MCP](https://www.anchorterminal.com/compare/deepgram-tts-vs-elevenlabs-tts.md)
- [Deepgram Text-to-Speech (Aura-2, Flux TTS) vs Fish Audio TTS API](https://www.anchorterminal.com/compare/deepgram-tts-vs-fish-audio-tts.md)
- [Deepgram Text-to-Speech (Aura-2, Flux TTS) vs Google Cloud Text-to-Speech](https://www.anchorterminal.com/compare/deepgram-tts-vs-google-cloud-tts.md)
- [Deepgram Text-to-Speech (Aura-2, Flux TTS) vs HeyGen Voice](https://www.anchorterminal.com/compare/deepgram-tts-vs-heygen-voice.md)
- [Deepgram Text-to-Speech (Aura-2, Flux TTS) vs Inworld Realtime TTS-2](https://www.anchorterminal.com/compare/deepgram-tts-vs-inworld-tts.md)
- [Deepgram Text-to-Speech (Aura-2, Flux TTS) vs MiniMax Speech (T2A)](https://www.anchorterminal.com/compare/deepgram-tts-vs-minimax-speech.md)
- [Deepgram Text-to-Speech (Aura-2, Flux TTS) vs Murf TTS API + MCP](https://www.anchorterminal.com/compare/deepgram-tts-vs-murf-tts.md)
- [Deepgram Text-to-Speech (Aura-2, Flux TTS) vs PlayHT Text-to-Speech API](https://www.anchorterminal.com/compare/deepgram-tts-vs-playht-tts.md)
- [Deepgram Text-to-Speech (Aura-2, Flux TTS) vs Resemble AI Text-to-Speech API](https://www.anchorterminal.com/compare/deepgram-tts-vs-resemble-ai-tts.md)
- [Deepgram Text-to-Speech (Aura-2, Flux TTS) vs Rime TTS API + MCP](https://www.anchorterminal.com/compare/deepgram-tts-vs-rime-tts.md)
- [Deepgram Text-to-Speech (Aura-2, Flux TTS) vs Soniox Text-to-Speech](https://www.anchorterminal.com/compare/deepgram-tts-vs-soniox-tts.md)
- [ElevenLabs Text to Speech API + MCP vs Smallest.ai Lightning TTS](https://www.anchorterminal.com/compare/elevenlabs-tts-vs-smallest-lightning-tts.md)
- [Fish Audio TTS API vs Smallest.ai Lightning TTS](https://www.anchorterminal.com/compare/fish-audio-tts-vs-smallest-lightning-tts.md)
- [Google Cloud Text-to-Speech vs Smallest.ai Lightning TTS](https://www.anchorterminal.com/compare/google-cloud-tts-vs-smallest-lightning-tts.md)
- [HeyGen Voice vs Smallest.ai Lightning TTS](https://www.anchorterminal.com/compare/heygen-voice-vs-smallest-lightning-tts.md)
- [Inworld Realtime TTS-2 vs Smallest.ai Lightning TTS](https://www.anchorterminal.com/compare/inworld-tts-vs-smallest-lightning-tts.md)
- [MiniMax Speech (T2A) vs Smallest.ai Lightning TTS](https://www.anchorterminal.com/compare/minimax-speech-vs-smallest-lightning-tts.md)
- [Murf TTS API + MCP vs Smallest.ai Lightning TTS](https://www.anchorterminal.com/compare/murf-tts-vs-smallest-lightning-tts.md)
- [PlayHT Text-to-Speech API vs Smallest.ai Lightning TTS](https://www.anchorterminal.com/compare/playht-tts-vs-smallest-lightning-tts.md)
- [Resemble AI Text-to-Speech API vs Smallest.ai Lightning TTS](https://www.anchorterminal.com/compare/resemble-ai-tts-vs-smallest-lightning-tts.md)
- [Rime TTS API + MCP vs Smallest.ai Lightning TTS](https://www.anchorterminal.com/compare/rime-tts-vs-smallest-lightning-tts.md)
- [Smallest.ai Lightning TTS vs Soniox Text-to-Speech](https://www.anchorterminal.com/compare/smallest-lightning-tts-vs-soniox-tts.md)

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