You have to log-in to SSA Business Services Online to e-file. There is a tab where you can see 'status'. I e-filed some 12/31/2025 and as of yesterday they still said received. I was waiting for processed.(When you upload them you should get a confirmation screen that says RECEIVED with a WFID (Wage File Identifier)).

W-3s do not get submitted.

I clicked on the .txt file and it opened. It's a bunch of gibberish but you can read employee names.