WhatsApp group chats used to have a maximum capacity of 256 users at once. For the most part it was more than enough, but for larger organizations or schools, it might not be sufficient, especially when you compare it to other messenger applications like Telegram which supports as many as 200,000 users at once.
The good news for those who might prefer WhatsApp is that in a recent update to the app, it looks like group chats will now be able to support as many as 512 users at once. We had previously heard that this feature was coming in a report last month, and now it looks like it is rolling out to users as we speak.
It seems to be a server-side update because not all users are seeing the option to have 512 members in a group chat at once, so if you don’t see it yet, give it some time and it should eventually make its way to you. This means that other than ensuring you have the latest version of the app, there’s nothing for you to do.
The change once it makes its way to your phone won’t require you to create new group chats to take advantage of it. Existing group chats should automatically support 512 users at once, so if you do have a group chat that is full, once the update arrives for your device, you can go ahead and start adding more members.
Source: Android Police