Why is my computer running out of disk space when I have not saved anything?
Space disappears into places you do not see in your documents folder, and a handful of categories account for nearly all of it.
System snapshots and restore points are usually the largest. Both major desktop operating systems keep automatic copies to enable rollback, and these can occupy an enormous amount without appearing anywhere obvious. They are also self-managing, which means they expand to fill available space by design.
Caches are the next category. Browsers, development tools, package managers and media applications all cache aggressively. A machine used for software development can easily hold many gigabytes of downloaded dependencies and build artifacts that nothing will ever clean automatically.
Log files grow quietly, particularly if something is erroring repeatedly. A single misbehaving application writing errors continuously can consume a great deal over weeks.
Cloud synchronisation folders deserve special attention because they are frequently misunderstood. Depending on configuration, files may be stored locally in full rather than streamed on demand, meaning your entire cloud storage occupies local disk.
Finally, deleted files in the recycle bin or trash still occupy space until emptied, and downloaded installer files accumulate indefinitely.
The practical approach is to use a disk usage analyser rather than guessing. These tools visualise which directories consume what, and the answer is usually obvious within seconds of looking. Deleting based on intuition tends to remove small things while missing the large one.
Be cautious about aggressive cleanup utilities that promise to reclaim space automatically. The built-in tools in both operating systems handle caches and snapshots safely, and third-party cleaners occasionally remove things applications still need.