This is the 11908th most frequent Russian word.
зарегистрировался
"Registered" or "signed up."
This sentence uses 'зарегистрировался' to indicate that someone has completed the process of signing up for a forum, emphasizing the action of registration.
Я зарегистрировался на новом форуме.
I registered on a new forum.
The word 'зарегистрировался' here highlights the act of checking in or officially enrolling for participation in an event or location.
Он зарегистрировался перед началом конференции.
He registered before the start of the conference.
In this context, 'зарегистрировались' means checking in at a location, such as a hotel, where details are officially recorded.