Should we transition to making our conference online or postpone? Last year we started organizing a conference in one of the European countries in September 2020. Everything was fixed and we had a number of registered people. As you all may know, due to the pandemic outbreak, many conferences in Europe were canceled. Since our conference was scheduled for September, we didn't declare it canceled and decided to wait a bit to see how the situation will be as we get close to the summer. 

Now, recently we thought about having an online conference instead of a real one. But we don't want it to be a failure as we have no experience with it and we are not aware of the public opinion about an online conference. 

Is it a good idea to change the conference to an online one or it is better to postpone the real conference until the end of this pandemic crisis?
Great question; however, I don't think there is any consensus opinion as to how good online conferences are. 

You might, however, read this blog post by Daniel Litt. He was an organizer of the Western Algebraic Geometry Online conference, held via Zoom this April. It was quite large, with around a thousand participants, and in my opinion very successful. 

In his blog post he discusses what went well, what went less well, and what the organizers tried to achieve. In summary, the organizers weren't able to replicate everything good about an in-person conference, but overall they succeeded in creating a very valuable experience for the participants.