“This project was created with a later version of After Effects and cannot be opened in this version”
What the error means, and three ways to fix it.
Why this happens
Every After Effects release can change the internal project-file format. To protect you from a half-broken open, After Effects reads the version number stored in the .aep/.aepx file and simply refuses to open it if the number is higher than what your installed copy supports. It doesn't matter whether the specific effects you used would actually work — the version check happens before AE even looks at the content.
Fix 1: Save a Copy As (if you have the newer version)
On the machine that has the newer After Effects installed: open the project, go to File > Save As > Save a Copy As, and pick the older version from the dropdown. This is Adobe's official method. The catch: it only steps back one version at a time, and you need that newer version of After Effects installed somewhere to run it.
Fix 2: Use an online downgrader
If neither of the above is practical — you don't have the newer version, nobody else does either, or you need to jump back multiple versions at once — our After Effects Downgrader rewrites the version marker in the project file directly, so the copy of After Effects you already have installed will open it. It's free for files up to 3MB and runs in your browser.
FAQ
Why can't I open a newer After Effects project in an older version?
After Effects project files store a version number, and each release can add project-format changes older builds don't understand. After Effects checks this number on open and refuses the file rather than risk showing something broken, even when most of the project would actually work fine.
How do I downgrade an After Effects project without installing the newer version?
Adobe's own "Save a Copy As" option requires having the newer version of After Effects installed first, and only steps back one version at a time. If you don't have that version, or need to jump back several versions at once, an online After Effects downgrader rewrites the file's version marker directly so your existing installed version will open it.
Will I lose effects or features when downgrading an AE project?
Any effect, expression, or feature that was introduced exclusively in a newer After Effects release won't be understood by an older build, regardless of which downgrade method you use. Everything else in the project keeps working normally.