Generate time-based OTPs. Even offline.
OTPea is an application you can use to authenticate on services that support time-based OTPs.
Common examples include Google, GitHub, ProtonMail, and WordPress.com. To see if your favourite service supports this, check Two Factor Auth List and look for a tick in the Software Token column.
When you enable two-factor authentication on these sites, they will provide a software token, a "secret". Once you add this secret to OTPea, it will generate a temporary password every 30 seconds, which the service will also recognize.
OTPea does not send your data anywhere outside your machine. Everything lives in your browser. So if you clear your browser data, OTPea will also forget your accounts.