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Avatar V

Highest fidelity. Opt-in per look.

Avatar IV

Default engine. Broadest coverage.

Avatar III

Photo-to-video pipeline. 4K.

HeyGen Voice

Voice clones and speech.
The v3 API exposes two kinds of models. Avatar rendering engines turn a look and a script into video, selected per request through the engine field on POST /v3/videos. The HeyGen Voice model clones a speaker and synthesizes speech, on its own or as the narration of an avatar video.

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Avatar rendering engines

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.
Before requesting an engine, confirm the look supports it: supported_api_engines on GET /v3/avatars/looks/{look_id} lists which of avatar_iii, avatar_iv, and avatar_v the look accepts. Requesting an engine that isn’t listed returns 400.
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. See Avatar III for the distinction.

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HeyGen Voice

HeyGen Voice is HeyGen’s in-house voice model. Clone a speaker at one of two tiers; the tier decides which endpoints you use afterward. Stock and designed voices from the voice catalog synthesize through the same Starfish path as instant clones.