Every step below is from an official source
Switch from 1Password to Google Password Manager
What to do at 1Password before you leave, what Google Password Manager 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 1Password, before you leave
Export from the 1Password desktop appBefore
On a Mac, open and unlock 1Password, select File > Export and choose the account. Pick 1PUX or CSV, then select Export Data.
How to export your data from the 1Password apps1Password Support. ReviewedExport passkeys from the iOS or Android appBefore
1Password says passkeys can only be exported in 1Password for iOS and Android at this time.
How to export your data from the 1Password apps1Password Support. ReviewedKnow what a CSV export leaves outBefore
A CSV export does not include security questions, linked items, linked apps or custom fields.
How to export your data from the 1Password apps1Password Support. ReviewedDelete the plaintext export file when doneAfter
Exported files are not encrypted and are stored in plaintext. Don't email them or store them online, and delete them when you are done.
How to export your data from the 1Password apps1Password Support. Reviewed
At Google Password Manager, when you join
Import a CSV file at passwords.google.comDuring
Go to passwords.google.com, select Settings, then Import, then Select File. Choose your file and select Import. Only .CSV files can be imported.
Import passwords to your Google Account - Google Account HelpGoogle. ReviewedImport up to 3,000 passwords at a timeBefore
You can import 3,000 passwords at a time. Your Google Account can store up to 10,000 passwords.
Import passwords to your Google Account - Google Account HelpGoogle. ReviewedDelete the CSV file after importingAfter
After the import, delete the .CSV password file. Otherwise anyone with access to the device can open it.
Import passwords to your Google Account - Google Account HelpGoogle. ReviewedSearch by site name for missing passwordsAfter
Not all app and site names move into the right field. If you can't find an imported password, search for the app or site name.
Then: everything else the switch affects
The steps above are what 1Password and Google Password Manager 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.