Methods, systems, and apparatus, including computer programs encoded on computer storage media, for account authentication. A method includes receiving a user request to include financial data describing a financial account in an interface, the financial account being associated with a financial institution. The method further includes redirecting the user to a first webpage associated with the financial institution, where the user inputs into the first webpage login credentials for accessing the financial account. The method further includes, in response to the user inputting into the first webpage login credentials for accessing the financial account, receiving, from the financial institution, an access token other than the login credentials for accessing the financial account. The method further includes storing the access token for use in accessing and aggregating financial data describing the financial account.