Render Frame at Markers is an After Effects script that automates single-frame output. It scans a composition for frames tagged by layer markers that fall within the comp work area and sends each one to the render queue. The result matches what you would get by moving to a point in time and choosing Save Frame As, File, done frame by frame across every marker.
Version 1.93 added the ability to use comp markers alongside layer markers, extending which frames the script can pick up. An earlier update, 1.92, added error suppression to address a CC2014 bug.
The script runs across a wide span of After Effects releases, from CS6 through CC and the 2020 to 2026 versions. It is listed here as free; check the developer's page for current licensing details.