I recommend using Pass or Keepass, because we can see the source code. But like all these password managers, you need to synchronize your password vault.
If you do not want to synchronize your vault among all your devices, but still want to have a unique password per site, try LessPass[1]. LessPass is a stateless open source password manager.
If you do not want to synchronize your vault among all your devices, but still want to have a unique password per site, try LessPass[1]. LessPass is a stateless open source password manager.
Disclaimer I am the creator of LessPass
[1] https://lesspass.com/