# Fish Audio TTS API vs HeyGen Voice

> HeyGen Voice scores 71.3 (BB) to Fish Audio TTS's 60.7 (C) for text-to-speech. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/fish-audio-tts-vs-heygen-voice
- Markdown: https://www.anchorterminal.com/compare/fish-audio-tts-vs-heygen-voice.md (~2,450 tokens)
- Slim: https://www.anchorterminal.com/compare/fish-audio-tts-vs-heygen-voice.min.md (~680 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/fish-audio-tts-vs-heygen-voice.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-10

HeyGen Voice scores 71.3 (BB) on agent readiness against Fish Audio TTS API's 60.7 (C), and leads in 4 of 7 scored categories. Both do text-to-speech.

- Fish Audio TTS API: grade C, 60.7/100, rank #505 of 961. Markdown https://www.anchorterminal.com/tools/fish-audio-tts.md · JSON https://www.anchorterminal.com/api/v1/tools/fish-audio-tts.json
- HeyGen Voice: grade BB, 71.3/100, rank #131 of 961. Markdown https://www.anchorterminal.com/tools/heygen-voice.md · JSON https://www.anchorterminal.com/api/v1/tools/heygen-voice.json
- Best text-to-speech APIs for AI agents: https://www.anchorterminal.com/best/text-to-speech/index.md
- All 66 tts comparisons: https://www.anchorterminal.com/compare/text-to-speech/index.md

## Which one, for what

### Fish Audio TTS API (C)

Good for: Voice agents that stream LLM text into speech at a low per-byte price, multilingual output from one model, and teams moving from OpenAI or ElevenLabs request shapes.

Watch for: The terms allow Usage Data and Content to train models, with no opt-out found

### HeyGen Voice (BB)

Good for: Speech in a voice cloned from one short recording, for agents that already make HeyGen videos or need a cloned narrator with streaming and timestamps.

Ahead on:
- Schema & documentation, 94 against 84
- Agent ergonomics, 83 against 67
- Security & auth, 69 against 35
- Transparency & trust, 69 against 60

Also in its favour:
- Agent-ready, a grade of BB or better

Watch for: Speaks only voices cloned in the caller's workspace. Stock and designed voices go through a separate endpoint and engines


## Score by category

| Category | Weight | Fish Audio TTS API | HeyGen Voice | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 75 | 75 | even |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 84 | 94 | HeyGen Voice +10 |
| Agent ergonomics | 13% (16.2 this run) | 67 | 83 | HeyGen Voice +16 |
| Security & auth | 14% (17.5 this run) | 35 | 69 | HeyGen Voice +34 |
| Payments & pricing | 10% (12.5 this run) | 30 | 30 | even |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 69 | 65 | Fish Audio TTS API +4 |
| Transparency & trust | 7% (8.8 this run) | 60 | 69 | HeyGen Voice +9 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **60.7 · C** | **71.3 · BB** | |

## Facts side by side

| Fact | Fish Audio TTS API | HeyGen Voice |
| --- | --- | --- |
| Kind | Model API | Model API |
| Vendor | Fish Audio | HeyGen |
| Hosted endpoint | `https://api.fish.audio` | `https://api.heygen.com` |
| Transports | HTTP, Streamable HTTP | HTTP |
| Auth | OAuth or key | API key |
| Pricing | Pay per use | Pay per use |
| x402 | no | no |
| Licence | Apache-2.0 (Python SDK), MIT (JavaScript SDK) | Closed service under HeyGen's Terms of Service (HeyGen Technology, Inc., last updated 23 July 2026). |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-09-23 | none |
| Terms last updated | 2024-08-18 |  |
| Privacy policy last updated | 2024-08-28 |  |
| Customer content may train models | yes |  |
| Terms restrict automated access | yes |  |
| Terms restrict benchmarking | yes |  |
| Terms or service can change without notice | not found in the text |  |
| Arbitration or class-action waiver | yes |  |
| Popularity | 5.2k npm/wk, 34k PyPI/wk | none |

## Verdicts

**Fish Audio TTS API.** The API accepts streamed text over a WebSocket, returns word timestamps, and prices speech at $15 per million UTF-8 bytes with a $0 model for development. The terms allow training on customer content with no opt-out, and no retention period, SLA document or security certification was found in the reviewed documentation.

**HeyGen Voice.** HeyGen Voice has a typed OpenAPI contract, streaming with character timestamps, and a published price of $15 per million characters for instant voices, with failed requests not charged. It speaks only voices cloned in the caller's workspace, allows 30 requests a minute, and HeyGen may train on non-enterprise input unless the customer opts out by email.

## Before you call either

### Fish Audio TTS API

1. Send the `model` header on every request and check its spelling. A missing or unknown value is served and billed as `s2.1-pro`.
2. Budget by UTF-8 bytes, not characters. Chinese, Japanese and Korean text costs about three bytes a character.
3. Retry 429 and 5xx with exponential backoff. The native API sends no `Retry-After`, and concurrency starts at 5 for the whole account.
4. Use `[bracket]` cues on the S2 family. `(parenthesis)` tags from `s1` are read aloud as text.
5. Pass the model explicitly in the JavaScript SDK, because npm release 0.1.0 defaults to `s1`.

### HeyGen Voice

1. Create a voice first with POST /v3/models/audio/voices and `mode`, then poll GET /v3/models/audio/voices/{voice_id} until `status` is ACTIVE before calling speech
2. Send `expressiveness_boost` only for instant voices and `seed`, `speed`, `pitch_shift`, `pitch_variance` or `<break>` tags only for professional voices. Mixing them returns 400 invalid_parameter
3. On the stream, decode and play each base64 WAV part in `part_index` order. Do not concatenate the bytes
4. Send an Idempotency-Key when creating a voice, and retry 502, 503 and 504 on speech, which the OpenAPI file marks as safe
5. Use POST /v3/voices/speech for stock or designed voices. It is a different engine and price

## Questions

### Which is better for AI agents, Fish Audio TTS API or HeyGen Voice?

HeyGen Voice scores 71.3 (BB) on agent readiness against Fish Audio TTS API's 60.7 (C), and leads in 4 of 7 scored categories.

### Do Fish Audio TTS API and HeyGen Voice need an API key?

Fish Audio TTS API takes an API key or an OAuth sign-in. HeyGen Voice needs an API key.

### Can an agent call Fish Audio TTS API and HeyGen Voice without installing anything?

Yes. Fish Audio TTS API has a hosted endpoint at https://api.fish.audio and HeyGen Voice at https://api.heygen.com.


## For agents

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

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