Internal domain transfers often referred to as a “push” domain transfer are most commonly the quickest method. Please know, it’s often advised by the domain registrar itself that this method is instantaneous. In our experience, it can still take a few days to complete. This process can be elongated if proper confirmation is not done by either buyer or seller to complete/initiate the domain transfer.
The external domain transfer process (auth code method) can take a bit longer. Once the transfer actually starts it will take 5-7 days for it to complete. Just like with the push domain transfer process this can be delayed by multiple factors. The domain can be ineligible for transfer, the auth code that’s being used is inaccurate (or it’s expired and another will need to be generated), or the domain name was not unlocked by the losing registrant.
However, unlike with push transfers, there is a method to expedite an external transfer. Once the transfer has started the losing registrant can acknowledge the transfer out which can often bypass the 5-7 day transfer requirement. Not all registrars make this a user-friendly process for the losing registrant and it’s often best to wait the 5-7 days for the domain to transfer normally.