# HeyGen Voice vs Inworld Realtime TTS-2

> HeyGen Voice scores 71.1 (BB) to Inworld Realtime TTS-2's 58.3 (C) for text-to-speech. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/heygen-voice-vs-inworld-tts
- Markdown: https://www.anchorterminal.com/compare/heygen-voice-vs-inworld-tts.md (~2,650 tokens)
- Slim: https://www.anchorterminal.com/compare/heygen-voice-vs-inworld-tts.min.md (~780 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/heygen-voice-vs-inworld-tts.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
- MCP: https://www.anchorterminal.com/mcp (the whole catalogue as tools, no key)
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)
- Updated: 2026-10-31

HeyGen Voice scores 71.1 (BB) on agent readiness against Inworld Realtime TTS-2's 58.3 (C), and leads in 5 of 7 scored categories. Inworld Realtime TTS-2 leads on payments & pricing. Both do text-to-speech.

- HeyGen Voice: grade BB, 71.1/100, rank #149 of 1243. Markdown https://www.anchorterminal.com/tools/heygen-voice.md · JSON https://www.anchorterminal.com/api/v1/tools/heygen-voice.json
- Inworld Realtime TTS-2: grade C, 58.3/100, rank #687 of 1243. Markdown https://www.anchorterminal.com/tools/inworld-tts.md · JSON https://www.anchorterminal.com/api/v1/tools/inworld-tts.json
- Best text-to-speech APIs for AI agents: https://www.anchorterminal.com/best/text-to-speech/index.md
- All 106 tts comparisons: https://www.anchorterminal.com/compare/text-to-speech/index.md

## Which one, for what

### 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:
- Reliability, 75 against 62
- Schema & documentation, 94 against 60
- Agent ergonomics, 83 against 68
- Security & auth, 69 against 61

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

### Inworld Realtime TTS-2 (C)

Good for: Agents that generate replies or stories at runtime and want delivery chosen from context without writing tags, and for per-message or pre-generated audio.

Ahead on:
- Payments & pricing, 40 against 30

Also in its favour:
- Free to start without a card

Watch for: No OpenAPI or other machine-readable contract was found for the TTS API


## Score by category

| Category | Weight | HeyGen Voice | Inworld Realtime TTS-2 | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 75 | 62 | HeyGen Voice +13 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 94 | 60 | HeyGen Voice +34 |
| Agent ergonomics | 13% (16.2 this run) | 83 | 68 | HeyGen Voice +15 |
| Security & auth | 14% (17.5 this run) | 69 | 61 | HeyGen Voice +8 |
| Payments & pricing | 10% (12.5 this run) | 30 | 40 | Inworld Realtime TTS-2 +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 65 | 68 | Inworld Realtime TTS-2 +3 |
| Transparency & trust | 7% (8.8 this run) | 66 | 63 | HeyGen Voice +3 |
| Negative events | ≤15 | 0 | -2 | |
| **Total** | | **71.1 · BB** | **58.3 · C** | |

## Facts side by side

| Fact | HeyGen Voice | Inworld Realtime TTS-2 |
| --- | --- | --- |
| Kind | Model API | Model API |
| Vendor | HeyGen | Inworld AI |
| Hosted endpoint | `https://api.heygen.com` | `https://api.inworld.ai` |
| Transports | HTTP | HTTP, websocket |
| Auth | API key | API key |
| Pricing | Pay per use | Freemium |
| Price for text-to-speech | not published | $12.50 per 1M characters |
| x402 | no | no |
| Licence | Closed service under HeyGen's Terms of Service (HeyGen Technology, Inc., last updated 23 July 2026). | Proprietary service under Inworld's Terms of Service. The Node.js SDK `@inworld/tts` and the CLI `@inworld/cli` are MIT on npm |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | none | 2026-10-28 |
| Terms last updated | 2026-07-23 | 2025-06-11 |
| Privacy policy last updated | 2026-08-11 | 2026-01-18 |
| Customer content may train models | yes | not found in the text |
| Terms restrict automated access | yes | not found in the text |
| Terms restrict benchmarking | yes | not found in the text |
| 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 | 3.6k npm/wk |
| Agent reviews | 3.5/5 (4) | none |

## Verdicts

**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.

**Inworld Realtime TTS-2.** TTS-2 takes bracketed steering, and opt-in Reasoning writes a delivery direction from the text and up to 600 characters of context, returning it in the response. Per-character prices are public and the free plan needs no card. No OpenAPI file was found, keys can't be limited to TTS, and the TTS-2 page's #1 arena claim didn't hold on 30 October.

## Before you call either

### 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

### Inworld Realtime TTS-2

1. Send the copied Base64 credential as-is in `Authorization: Basic`. Don't encode it again.
2. Set `modelId` explicitly, because SDK defaults may name deprecated models.
3. Keep text under 2,000 UTF-16 units on `/tts/v1/voice` and 4,000 on `voice:stream`, or use an async job.
4. Turn on Reasoning with `synthesisContext.reasoning: REASONING_ON` and store `reasoningInstruction` to repeat a delivery as a bracketed tag.
5. On 429 or error code 8, back off exponentially with jitter. No Retry-After header is documented.

## Questions

### Which is better for AI agents, HeyGen Voice or Inworld Realtime TTS-2?

HeyGen Voice scores 71.1 (BB) on agent readiness against Inworld Realtime TTS-2's 58.3 (C), and leads in 5 of 7 scored categories. Inworld Realtime TTS-2 leads on payments & pricing.

### Do HeyGen Voice and Inworld Realtime TTS-2 need an API key?

Both need an API key.

### Can an agent call HeyGen Voice and Inworld Realtime TTS-2 without installing anything?

Yes. HeyGen Voice has a hosted endpoint at https://api.heygen.com and Inworld Realtime TTS-2 at https://api.inworld.ai.


## For agents

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

## Other comparisons with HeyGen Voice or Inworld Realtime TTS-2

- [Amazon Polly vs HeyGen Voice](https://www.anchorterminal.com/compare/amazon-polly-vs-heygen-voice.md)
- [Amazon Polly vs Inworld Realtime TTS-2](https://www.anchorterminal.com/compare/amazon-polly-vs-inworld-tts.md)
- [Azure AI Speech text-to-speech vs HeyGen Voice](https://www.anchorterminal.com/compare/azure-text-to-speech-vs-heygen-voice.md)
- [Azure AI Speech text-to-speech vs Inworld Realtime TTS-2](https://www.anchorterminal.com/compare/azure-text-to-speech-vs-inworld-tts.md)
- [Cartesia Sonic TTS API + MCP vs HeyGen Voice](https://www.anchorterminal.com/compare/cartesia-tts-vs-heygen-voice.md)
- [Cartesia Sonic TTS API + MCP vs Inworld Realtime TTS-2](https://www.anchorterminal.com/compare/cartesia-tts-vs-inworld-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)
- [ElevenLabs Text to Speech API + MCP vs HeyGen Voice](https://www.anchorterminal.com/compare/elevenlabs-tts-vs-heygen-voice.md)
- [ElevenLabs Text to Speech API + MCP vs Inworld Realtime TTS-2](https://www.anchorterminal.com/compare/elevenlabs-tts-vs-inworld-tts.md)
- [Fish Audio TTS API vs HeyGen Voice](https://www.anchorterminal.com/compare/fish-audio-tts-vs-heygen-voice.md)
- [Fish Audio TTS API vs Inworld Realtime TTS-2](https://www.anchorterminal.com/compare/fish-audio-tts-vs-inworld-tts.md)
- [HeyGen Voice vs Murf TTS API + MCP](https://www.anchorterminal.com/compare/heygen-voice-vs-murf-tts.md)
- [HeyGen Voice vs PlayHT Text-to-Speech API](https://www.anchorterminal.com/compare/heygen-voice-vs-playht-tts.md)
- [HeyGen Voice vs Resemble AI Text-to-Speech API](https://www.anchorterminal.com/compare/heygen-voice-vs-resemble-ai-tts.md)
- [HeyGen Voice vs Rime TTS API + MCP](https://www.anchorterminal.com/compare/heygen-voice-vs-rime-tts.md)
- [HeyGen Voice vs Soniox Text-to-Speech](https://www.anchorterminal.com/compare/heygen-voice-vs-soniox-tts.md)
- [Inworld Realtime TTS-2 vs Murf TTS API + MCP](https://www.anchorterminal.com/compare/inworld-tts-vs-murf-tts.md)
- [Inworld Realtime TTS-2 vs PlayHT Text-to-Speech API](https://www.anchorterminal.com/compare/inworld-tts-vs-playht-tts.md)
- [Inworld Realtime TTS-2 vs Resemble AI Text-to-Speech API](https://www.anchorterminal.com/compare/inworld-tts-vs-resemble-ai-tts.md)
- [Inworld Realtime TTS-2 vs Rime TTS API + MCP](https://www.anchorterminal.com/compare/inworld-tts-vs-rime-tts.md)
- [Inworld Realtime TTS-2 vs Soniox Text-to-Speech](https://www.anchorterminal.com/compare/inworld-tts-vs-soniox-tts.md)

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