Dropbox

Dropbox is a cloud storage and file synchronization service, one of the earliest to make a synced folder work reliably across machines.

Its sync engine remains its strongest technical asset: block-level updates mean editing a large file re-uploads only the changed portion, which matters for teams working on big assets.

Its free tier is small compared with competitors bundled into operating systems, so the case for paying is usually sync reliability and sharing controls rather than raw capacity.