Find your save
On Windows, Factorio keeps saves in %APPDATA%\Factorio\saves. Each save is a .zip named after it, and autosaves are named _autosave1.zip, _autosave2.zip and so on. Pick the newest.
Match the save
- Space Age: set Game mode in Settings to match. A Space Age save needs Space Age, and every player needs the expansion.
- Mods: upload the save's mods (each mod's .zip) to mods/ in Files & SFTP.
Upload it
- Upload the save. In Files & SFTP, choose world-imports/ and press Upload to world-imports, then pick the save's .zip. Up to 96 MB uploads in the browser; a bigger save goes to world-imports over SFTP (Generate SFTP credentials).
- Wait for the safety scan. Every upload is scanned before your server gets it. Press Refresh until the zip shows Passed safety scan.
- Stop and start the server. Press Stop, then Start. The save replaces the one the server runs, and the next backup keeps it.
Good to know
Upload the save's .zip just as Factorio made it: don't unzip it or zip it again. The server checks that it's a Factorio save, and keeps its current one if it isn't.