Breaking

HeyGen Adds Transparent WebM Output to Its Video API, CLI, and MCP for Alpha-Channel Avatars

July 11, 2026 at 17:10 EDT

Media Generation
AI Agents

HeyGen has enabled transparent WebM video output across its API, command-line interface, and Model Context Protocol integration, allowing AI-generated avatars to be delivered with a real alpha channel and no green screen. The feature lets developers set output_format: "webm" on the POST /v3/videos endpoint to receive an avatar clip with a genuine transparent background ready for compositing.

New Capability · HeyGen API

Transparent Avatars, No Green Screen

Setting output_format: "webm" now delivers AI avatars with a genuine alpha channel — ready to composite straight into any scene, across the API, CLI, and MCP.

WebM

Container with native per-pixel transparency

Surfaces exposed: API · CLI · MCP

Engines supported: Avatar III, IV, V

Old MP4 vs New WebM

MP4 · solid background

No alpha channel — manual cleanup needed

→

WebM · true transparency

Real alpha channel — composite anywhere

SUPPORTED

Recent Digital Twin & Studio Avatars
Avatar III, Avatar IV (default), Avatar V
Background removal applied automatically

CAVEATS

Requires an avatar trained with matting
Older avatars return an error
Cinematic Avatars not supported
May need transcoding downstream

Agent-Ready Pipeline

AI Agent

via MCP server

→

Request WebM

transparent avatar

→

Composite

into any scene

The same capability reaches agents operating over HeyGen's remote MCP server — enabling fully automated, layered-video pipelines built around assistants like Claude Code.

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