Blender
Blender is a GPL-3.0-or-later 3D creation suite with a node compositor, a video sequencer, motion tracking, masking, keying and a full 3D pipeline. It runs on Windows, macOS and Linux. For an After Effects user, the relevant parts are the Compositor workspace, the Movie Clip Editor for tracking, and the ability to combine rendered 3D elements with live footage.
Its strength is range. Camera tracking, planar tracking, rotoscoping, keying, colour correction, lens distortion and 3D titles can all be done inside one application, and the result can be rendered through the same node graph. Geometry, particles and simulation add options that After Effects does not provide natively.
The break is the mental model and the ecosystem. Blender’s compositor is node-based, not a layer stack with a timeline, and its text and shape animation tools are less convenient for broadcast graphics. After Effects project files, templates and most third-party plug-ins do not transfer. Learning the compositor well enough to replace a familiar workflow takes time, and render performance depends heavily on the machine and the scene.