You hit render, the progress bar crawls to 4%, and After Effects throws "Unable to allocate 0.000 MB of memory" at you like it's doing you a favor. Annoying.
Here's the deal: that 0.000 MB number is a lie. It doesn't mean AE needed zero memory. It means AE tried to allocate a block, the allocator returned nothing, and the error handler printed the requested size instead of the failing size. The real culprit is almost always the disk cache, not your RAM.
The fix (do these in order)
- Purge the disk cache first. Close After Effects. Then delete the cache folder manually — don't rely on the Edit menu purge, it leaves files behind when things are this broken.
On Windows, the default path is:
C:\Users\<YourName>\AppData\Roaming\Adobe\Common\Media Cache Files
C:\Users\<YourName>\AppData\Roaming\Adobe\Common\Media CacheOn macOS:
/Users/<YourName>/Library/Application Support/Adobe/Common/Media Cache Files
/Users/<YourName>/Library/Application Support/Adobe/Common/Media CacheNuke both folders. Yes, all of it. AE will rebuild what it needs.
- Check the scratch disk in Preferences. Open After Effects, go to Edit > Preferences > Media & Disk Cache (Windows) or After Effects > Settings > Media & Disk Cache (macOS). Look at the "Disk cache location" field. If it points to your C: drive and C: has under 50 GB free, that's your problem. Change it to a drive with actual room. An SSD is best. A spinning USB drive is not.
- Set the cache size sanely. The default in recent versions is around 50 GB. On a cramped drive, drop it to 20–30 GB. On a big scratch SSD, crank it to 100+ GB. Just make sure the drive has at least 2x the cache size in free space.
- Clear any per-project memory overrides. Weird one, but it bites people: some templates ship with hidden memory settings baked in. Open Edit > Purge > All Memory & Disk Cache, then save the project under a new name and reopen.
- Disable multiprocessing on old machines. If you're on a quad-core with 16 GB RAM and the error pops during preview, go to Preferences > Memory & Performance and uncheck "Render multiple frames simultaneously." This feature has been the source of more false memory errors than any single bug.
Why this works
After Effects uses a tiered memory model. RAM for live preview, then a disk cache for anything that doesn't fit, then a scratch disk spillover for renders. When the disk cache drive fills up or the cache files get corrupted, AE's allocator tries to grab a block, gets refused by the OS, and reports it as a memory allocation failure. The "0.000 MB" is just the size of the block it was asking for at the moment of failure — often a rounding artifact from a 0-byte placeholder allocation.
Clearing the cache forces AE to rebuild its index files. Pointing the cache to a drive with real free space gives the allocator somewhere to write. That combination fixes this in probably 85% of cases I've seen.
Less common causes
Corrupt project file
If the error happens on one specific comp and not others, the project itself is bad. Import your comps into a fresh project via File > Import > After Effects Project. Don't just Save As — actually import. This rebuilds internal references.
Third-party plugins hogging memory
Trapcode, Element 3D, and some BorisFX plugins can leak memory on specific versions. Test by disabling half your plugins via the Manage Plug-ins menu, then toggling back in batches until the error returns. Real-world trigger I've seen: Element 3D v2.2 on AE 2021 leaking ~2 GB per frame render on scenes with more than 40 3D objects.
Windows page file set to 0
Somebody followed a "gaming optimization" guide and disabled the page file. After Effects needs it even with 64 GB RAM because it demands contiguous virtual memory blocks that Windows won't commit without a swap file.
System Properties > Advanced > Performance Settings > Advanced > Virtual Memory > Change
Set to System managed size on your fastest SSD.Font cache corruption
Rare but real. Delete FNTCACHE.DAT from C:\Windows\System32 after booting into Safe Mode. AE builds font caches on launch and a corrupt one cascades into allocator failures.
Antivirus scanning the cache folder
Bitdefender and Avast are the usual offenders. They lock cache files mid-write and AE sees the lock as a failed allocation. Add the Adobe Common Media Cache folder as an exclusion.
Prevention
- Dedicate a separate SSD to scratch and cache. 500 GB minimum. This one change eliminates the majority of memory errors I've dealt with.
- Keep at least 20% of every drive free. Windows and macOS both get weird when drives are packed.
- Purge disk cache weekly if you're doing heavy work. Takes 30 seconds, saves an afternoon.
- Match your AE version to your plugin versions. Chasing latest-and-greatest on both sides is how you get allocator bugs that nobody's documented yet.
- Update your GPU driver. Sounds basic, but AE 2023 + Studio Driver 531 vs 537 had wildly different memory behavior on the same hardware.
If you've done all of the above and it still fails, run AE with verbose logging: launch from a command line with AfterFX.exe -m on Windows, or check the log at ~/Library/Preferences/Adobe/After Effects/<version>/AfterFX.log on macOS. The trace will tell you which allocation failed and roughly where. That's the point where you file a bug with Adobe and, honestly, roll back a version.