Every step below is from an official source
Switch from Proton Pass to Bitwarden
What to do at Proton Pass before you leave, what Bitwarden needs when you join, and everything else the switch touches. Your full plan is built in your browser and stays there.
Official sources reviewed . How we review sources
At Proton Pass, before you leave
Export from Proton Pass settingsBefore
In the browser extension, web app or Windows app, open settings with the gear icon, then click the Export tab.
How to export from Proton PassProton Support. ReviewedUse a computer, not the mobile appBefore
You can't export data from the Proton Pass mobile apps.
How to export from Proton PassProton Support. ReviewedEncrypt the export if you store or send itDuring
You can export a ZIP with a PGP-encrypted JSON file, an unencrypted ZIP, or a CSV file. Proton recommends encrypting the file if you will keep it as a backup or transfer it.
How to export from Proton PassProton Support. Reviewed
At Bitwarden, when you join
Import from LastPass, 1Password, Chrome and moreDuring
Bitwarden supports imports from common password managers, including LastPass, 1Password, Firefox, Chrome, Edge, Chromium, Password Safe and other Bitwarden vaults.
Import to your vault or collectionsBitwarden Help Center. ReviewedImport LastPass directly, then add attachments by handDuring
Bitwarden's browser extensions and desktop apps can import your individual LastPass vault directly, with no file upload. File attachments and trash must be uploaded to your vault by hand.
Import from LastPassBitwarden. ReviewedSplit files with more than 40,000 itemsBefore
An imported file can contain up to 40,000 items. If your file is too large, split it into smaller files and import each one.
Import to your vault or collectionsBitwarden Help Center. ReviewedDelete the export file after importingAfter
Once your data is in Bitwarden, delete the exported data file from your computer.
Import to your vault or collectionsBitwarden Help Center. Reviewed
Then: everything else the switch affects
The steps above are what Proton Pass and Bitwarden say. Your full checklist adds the accounts, codes, payments and devices that depend on your password manager, in a safe order. It's built from your answers, in your browser.