HeyGen Avatar Rendering Engines

HeyGen has three avatar rendering engines, all available on the v3 API and selected per request through the engine field on POST /v3/videos. New integrations should default to Avatar IV for broad coverage, opt into Avatar V for the highest-fidelity motion and lip-sync, and use Avatar III for its dedicated photo-to-video pipeline.

{
  "type": "avatar",
  "avatar_id": "YOUR_LOOK_ID",
  "script": "Hello from HeyGen.",
  "voice_id": "YOUR_VOICE_ID",
  "engine": { "type": "avatar_iv" }
}

Before requesting an engine, confirm the avatar look supports it by checking supported_api_engines on the look (GET /v3/avatars/looks/{look_id}) — the array lists which of avatar_iii, avatar_iv, and avatar_v the look accepts, and requesting an engine that isn’t listed returns a 400 error.

Choosing an engine

	Avatar V	Avatar IV	Avatar III
`engine.type`	`avatar_v`	`avatar_iv`	`avatar_iii`
API version	v3	v3	v3
Default engine	✗ (explicit opt-in)	✓	✗ (explicit opt-in)
Available to new users	✓	✓	✓
Digital Twin	✓	✓	✓
Photo Avatar	✗	✓	✓ (dedicated pipeline)
Studio Avatar	✗	✓	✓ (renders as Digital Twin)
Arbitrary image input	✗	✓	✗
`motion_prompt`	✓	✓	✗
`expressiveness`	✗	✓	✗
Cross-reference animation	✓	✗	✗
4K output	✗	✗	✓ (except Photo Avatar)
Eligibility check required	✓	✗	✗

A separate, older Avatar III engine remains available to existing customers through the legacy v1/v2 endpoints. It uses a different pipeline and is not the same as the Avatar III (avatar_iii) engine documented here. It is not offered on the new developer platform. See Avatar III for the distinction.

⌘I