What’s the safest way to free up space on a nearly full Windows C: drive?

First find out what is actually using the space instead of deleting folders at random. WinDirStat, TreeSize Free, and SpaceSniffer can show the largest folders and files. Run the tool as administrator if needed, but treat system directories as read-only unless you know exactly what a file is. Pay particular attention to large downloads, videos, old installers, application data, and system restore data.

Use Windows Settings > Apps to uninstall programs you no longer need, then review your Downloads, Desktop, Documents, Pictures, and Videos folders. Move personal files to another drive or external backup before deleting them, and empty the Recycle Bin afterward. You can also run Disk Cleanup as administrator and remove temporary files, update cleanup files, and other categories that Windows explicitly identifies as safe.

With only 1 GB free, a larger drive may be the best long-term fix. A 1 TB SSD can usually be cloned from the existing system drive if the hardware supports it, but make a verified backup first. Windows needs working space for updates and temporary operations, so try to keep substantially more free space than you have now.

Temporary files are worth checking, including the folder opened by typing %temp% in the Run dialog. Delete what Windows allows and skip anything that is currently in use. Avoid manually deleting files inside C:Windows, C:WindowsInstaller, or component-store folders; those can be needed for updates, repairs, and uninstalling software. Also avoid wiping tools such as DBAN, since they erase entire drives rather than selectively freeing space.