The Free Fire OB53 Advance Server, which concluded in early April 2026, provided early access to "Undersea Mystery" content and rewards for reporting bugs

As of this article’s publication, here is the typical schedule:

The Advance Server is currently closed . You can still visit the official site to check for the next registration period, which usually begins roughly 2–3 weeks before a major update. How the Program Works

The Free Fire Advance Server is a temporary, Android-only testing environment for the upcoming OB53 update, allowing players to experience new features before global release

https://reward.ff.garena.com/en/advancedserver