Yes, your drive choice affects After Effects performance, and it matters most for cache and scratch files

After Effects will run on any drive with enough free space, but where you install it and where you point it to store working files creates a real difference in how fast your timeline scrubs, how quickly previews render, and whether your system crashes mid-project. The software itself can live on your main drive, but your scratch disk—the place After Effects writes temporary data while you work—should be on a separate, fast drive if you have one. If you're working with 4K footage or complex compositions, this choice goes from "nice to have" to "necessary."

The reason is straightforward: After Effects is constantly reading and writing. When you play back a timeline, it's pulling video frames from your source files, processing effects in real time, and writing preview data to the scratch disk simultaneously. If all of that traffic flows through one drive, you create a bottleneck. A second drive—especially a fast SSD—handles the scratch work while your main drive handles the source footage, and your system breathes.

Key Takeaways

  • After Effects can be installed on your main drive, but scratch disk (cache and preview files) should be on a separate, fast SSD if possible.
  • Using the same drive for source footage, the process, and scratch files creates read/write bottlenecks that slow playback and increase crash risk.
  • You set your scratch disk location in After Effects preferences, not during installation, so you can change it anytime without reinstalling.
  • A full scratch disk will cause After Effects to freeze or crash, so monitor free space and clear old cache files regularly.
  • NVMe SSDs are faster than SATA SSDs for scratch work, but any SSD beats a hard drive for After Effects performance.

What After Effects actually stores on your scratch disk

After Effects creates several types of temporary files, and all of them go to your scratch disk by default. The biggest is the disk cache—when you play back a timeline, After Effects renders each frame and stores it here so the next time you scrub to that same frame, it plays when ready instead of re-rendering. On a 4K project with effects, a few minutes of timeline can consume 10 to 50 GB of cache.

The software also writes preview files (lower-resolution versions of your composition used for faster playback), conformed audio (audio converted to a format After Effects can work with quickly), and temporary project data while you work. None of these files are permanent—After Effects deletes them when you close the project—but while you're working, they're constantly being written and read.

If your scratch disk is slow or full, After Effects has to wait for these writes to complete before it can show you the next frame. On a fast SSD, the wait is invisible. On a slow drive or one that's nearly full, you see stuttering playback, delayed scrubbing, and eventually crashes when the drive runs out of space.

Installation drive versus scratch disk: they're separate decisions

When you install After Effects, you choose where the process files go—the executable, the plugins, the libraries. This is your installation drive. But After Effects has a separate setting for where it stores working files, and you configure this in Preferences > Media & Disk Cache after installation. You don't have to reinstall the software to change your scratch disk; you just point it to a different location.

Most people install After Effects on their main drive (usually C: on Windows or Macintosh HD on Mac) because that's where the operating system expects applications to live. That's fine. What matters is that your scratch disk is somewhere else—ideally a dedicated SSD that's not your boot drive and not the drive holding your source footage.

If you only have one drive, you can still use After Effects, but performance will suffer with large projects. The software will be reading source files, writing cache, and running the operating system all from the same physical disk, and that creates contention. If you're working with HD footage and straightforward effects, you might not notice. With 4K or heavy color grading, you will.

Why a separate drive makes the biggest difference

A modern SSD can read and write at 400 to 7,000 MB per second depending on the type (SATA versus NVMe). A hard drive maxes out around 150 MB per second. When After Effects is pulling 4K video frames (which can be 100+ MB per frame) from your source drive and simultaneously writing preview data to your scratch disk, having two separate drives means both operations happen in parallel. If they're on the same drive, one has to wait for the other.

The speed difference is measurable. On a single hard drive, a 4K timeline with effects might preview at 5 frames per second. Move the scratch disk to an SSD on a different controller, and you might see 24 fps. That's not a small improvement—that's the difference between working and not working.

The type of SSD also matters. An NVMe drive (which connects directly to your motherboard) is faster than a SATA SSD (which uses an older connection standard). But even a SATA SSD is dramatically faster than a hard drive for After Effects work. If you're buying a second drive specifically for scratch, NVMe is the better choice, but SATA will still transform your workflow.

How to set your scratch disk in After Effects

Open After Effects and go to Edit > Preferences > Media & Disk Cache (Windows) or After Effects > Preferences > Media & Disk Cache (Mac). You'll see a section labeled "Disk Cache" with a folder path and a button to change it. Click the button and navigate to the drive and folder where you want After Effects to store cache files. You can create a new folder if you want—something like "AE_Cache" makes it straightforward to find later.

After Effects will ask if you want to move existing cache to the new location. Usually you'll say no, because old cache from previous projects isn't worth keeping. Just let it start fresh on the new drive.

You can also set a maximum size for the disk cache in the same window. After Effects will delete old cache files once it hits this limit, so it won't fill your drive. A reasonable starting point is 50 GB if you have the space, but adjust based on your project size and available drive capacity. Leave at least 10 to 20 percent of your drive free so the operating system has room to work.

Monitoring and clearing your scratch disk

After Effects doesn't always clean up after itself perfectly, especially if you force-quit the software or it crashes. Over time, orphaned cache files can accumulate and waste space. You can manually clear the cache by going to Edit > Purge > All Memory (which clears RAM cache) and Edit > Purge > Disk Cache (which deletes the files on your scratch disk). Do this between projects to keep things tidy.

Check your scratch disk's free space regularly, especially if you're working on long or complex projects. If free space drops below 10 percent, After Effects will start to slow down or freeze. If it hits zero, the software will crash. You can see how much cache After Effects is using by going to Preferences > Media & Disk Cache and looking at the "Current Size" readout.

If you're working on a tight important date and your scratch disk is getting full, the fastest fix is to close After Effects, manually delete the cache folder (it's safe to delete—After Effects will recreate it), and restart the software. This is faster than waiting for the purge function to run through thousands of files.

What to do if you only have one drive

If your computer has only one SSD and you can't add another, After Effects will still work, but you'll need to manage your workflow carefully. Set your scratch disk to a folder on that same drive, but make sure you have at least 100 GB free before starting a project. Work with smaller sequences or lower-resolution proxies (downsampled versions of your footage) to reduce cache size. Purge your disk cache between projects so old files don't accumulate.

You can also reduce the disk cache size limit in preferences to something like 20 or 30 GB, which forces After Effects to delete old cache more aggressively. This keeps the drive from filling up, but it means you'll re-render frames more often when you scrub backward in your timeline.

If you're regularly working with 4K footage or complex effects on a single-drive system, adding a second SSD is one of the highest-return upgrades you can make. It's cheaper than upgrading RAM or the CPU, and the performance gain is when ready and obvious.

Frequently Asked Questions

Can I use an external drive as my scratch disk?

Yes, but only if it's fast enough. A Thunderbolt 3 or USB 3.1 external SSD works well. USB 2.0 or older external hard drives are too slow and will make After Effects nearly unusable. If you're using an external drive, keep it plugged in and don't move it while After Effects is running, or you'll lose the cache and crash the software.

What happens if my scratch disk fills up while I'm working?

After Effects will freeze, then crash. You'll lose any unsaved work in your current session. The software can't write new cache frames if there's no space, so it stops responding. Always leave at least 10 to 20 percent of your scratch disk free, and check the available space before starting a long render or preview.

Should I put my source footage on the same drive as my scratch disk?

No. Ideally, you want three separate drives: one for the operating system and After Effects installation, one for source footage, and one for scratch disk. If you only have two drives, put After Effects and the OS on one, and use the second for both source footage and scratch disk. Having source and scratch on the same drive is better than having everything on one drive, but separate is still better.

Do I need to reinstall After Effects if I change my scratch disk location?

No. You can change your scratch disk location anytime in Preferences without reinstalling. After Effects will start using the new location when ready. You can even have multiple scratch disk locations if you want to spread the load across several drives.

Is an NVMe drive worth the extra cost for After Effects?

For most projects, a SATA SSD is fast enough and costs less. NVMe is noticeably faster with very large files or complex timelines, but the difference is smaller than the jump from a hard drive to any SSD. If you're buying new and the price difference is small, go NVMe. If you already have a SATA SSD, it will serve you well.