In some cases WinSCP needs to download remote files to some temporary location on your computer. This includes:

• Editing, opening or creating remote file locally.
• Downloading file using drag&drop without the shell extension.
• Using local custom command on remote file.

Normally WinSCP removes the temporary files on its exit at the latest. When WinSCP is not closed correctly for whatever reason or it just cannot remove the files because they are still opened in an external aplication (text editor), the temporary files remain on your computer.

For the reason WinSCP does additional check on its startup for presence of obsolete temporary folders. By default it will ask you before removing them. But you can configure it to remove them automatically.

You can remove the obsolete temporary folders also manually from Cleanup dialog.

By default WinSCP stores temporary files in system temporary folder (usually defined by TMP or TEMP environment variables). You can change the location in preferences.