An AEP file is the standard After Effects project format that outlines how your video is built rather than producing a playable export, capturing compositions, Layer elements of all types, animation data such as motion parameters, effect setups, masks, mattes, plus cameras and lights in 3D space, and since it usually references media instead of embedding it, the AEP stays compact even when the project draws on large external assets.

After Effects shows “footage offline” when an AEP’s linked assets are moved or excluded during transfer, which is why proper relocation usually involves Collect Files or manually assembling the AEP and every referenced element into one package, and if an AEP doesn’t behave like an AE file, clues like its download source, neighboring files, Windows associations, or a read-only glance in a text editor can confirm whether it’s a real After Effects project or a different type entirely.

For more information on AEP file structure check out our own site. When an AEP seems to go “broken” on a different PC, the cause is almost always that it functions as a reference-based blueprint instead of a self-contained package, with After Effects saving absolute file paths to video, images, audio, and proxy files, and when the project lands on a machine where those paths don’t match due to new drive letters, folder differences, or absent assets, AE loads the project but reports Missing/Offline Media until you reconnect the files.

A project may look “broken” even with footage intact when the new machine lacks specific fonts—forcing text to substitute—or missing plugins that leave effects unreadable, or when using an older After Effects version that can’t interpret newer features, and the dependable solution is to use Collect Files or replicate the folder layout exactly and then relink, at which point matching fonts, plugins, and paths generally restore the project immediately.

An AEP file works as a lean project database that can represent a full motion-graphics project without the storage weight of footage, containing comp attributes like resolution, frame rate, length, nesting, and background, all timeline layers and their transforms such as placement values, scale, rotation, opacity, blending, track mattes, parenting, timing, plus animation instructions including keyframes, easing curves, motion blur, markers, expressions, effect parameters, and mask/roto data like contour shapes, feather, expansion, and animated points.

With 3D enabled, the AEP records camera rigs, lighting setups, 3D layer options, and render configurations, plus project-organization elements such as bins, label colors, interpretation settings, and occasional proxy assignments, but not the actual footage files—your videos, images, and audio stay external—meaning the AEP is mostly the construction plan and the paths to media, so if you relocate assets, After Effects reports missing items until you relink.