Computer A is signed into your Mozilla account with the sync options checked. see screenshot When you sign into the browser on Computer B with the same account, your checked options should start showing in the browser on Computer B. Then from Computer B, you should be able to see and open the open tabs on Computer A on Computer B. see screenshots '''FYI... SYNC IS NOT A DATA BACKUP SERVICE''' Sync info... https://support.mozilla.org/en-US/kb/how-do-i-set-sync-my-computer https://support.mozilla.org/en-US/kb/how-do-i-choose-what-information-sync-firefox https://www.mozilla.org/en-US/firefox/features/sync/ https://hacks.mozilla.org/2018/11/firefox-sync-privacy/ '''Sync is not a backup tool but it is a good sync/transfer/move tool''' https://support.mozilla.org/en-US/forums/contributors/707681