Sequence Shuttle keeps a local cache — a copy of recently used file data stored on disk — so that reopening a file you've already worked with reads from disk instead of downloading it from the cloud again. Shuttle actually keeps two caches at once: a small in-memory (RAM) cache for instant access to whatever you touched moments ago, and a larger on-disk cache that persists even after you quit Shuttle or restart your Mac. The disk cache does the heavy lifting — once part of a file has been downloaded into it, reopening that file, or scrubbing back through footage you've already played, reads from local disk instead of over the network.
This caching is most noticeable during playback. When you play or scrub a clip, Shuttle begins prefetching — downloading footage ahead of your playhead in the background, before you reach it — so playback keeps up without waiting on the network. The longer playback continues without interruption, the further ahead Shuttle downloads, so sustained playback of a clip stays smooth.
You control how much disk space the cache can use. Click the Shuttle icon in the menu bar, choose Settings, and look at the Cache section: Size sets the maximum the disk cache can grow to — anywhere from 1 GB up to 1 TB, 100 GB by default — and Cache Location shows where on disk it currently lives, with Change… and Reset available to move it. The RAM cache, by contrast, is fixed at 1 GB and isn't something you can adjust — the size you're actually managing is the disk cache. The Cache section also lets you check current usage at a glance and clear the cache outright when you want to start fresh.
Shuttle also watches how much of your configured cache limit is still free — comparing current cache usage against the Size you set, not the physical disk — and steps in automatically before the cache fills up. With 20% or more of that limit still free, nothing changes — uploads and caching continue as normal. Once the free headroom drops below 20%, Shuttle throttles uploads to conserve what's left. If it keeps falling below 10%, Shuttle goes further and starts actively freeing space itself, removing the least recently used cached file data in the background until the headroom recovers.
Note
Automatic cleanup only removes cached copies of files that have already finished uploading — the original is already safe in the cloud before the local copy is cleared. A file that's still mid-upload or mid-write is never touched, so nothing you're actively working on is at risk.
If you revisit a file after its cached copy has been cleaned up this way, Shuttle downloads it again — the same way it did the first time you opened it. So if a familiar file suddenly takes a moment to open, or an upload seems to slow down while disk space is tight, that's Shuttle quietly managing the cache and disk space in the background rather than a sign that something's wrong.