The Rematch beta has had several phases:
- The initial Rematch beta ran from April 18, 2025, 3 PM (UTC) to April 21, 2025, 8 AM (UTC).
- The final beta took place from May 28, 2025, at 12 PM GMT to May 31, 2025, at 12 PM GMT (or May 31, 5 AM PT / 8 AM ET / 12 PM UTC).
- The open beta officially ended on May 31, 2025.
After May 31, 2025, the beta phase concluded, and the full game release was set for June 19, 2025. So, to directly answer your question, the Rematch beta ended on May 31, 2025.
