PlayFab (by Microsoft)
Great for multiplayer, leaderboards, user accounts, cloud scripting, and real-time analytics. Unity SDK available.
Firebase (by Google)
Ideal for authentication, real-time database, cloud functions, and push notifications. Lightweight, scalable, and free tier available.
GameSparks (Now part of AWS)
Advanced backend with matchmaking, leaderboards, and cloud code. Better for mid to large-scale games.
Photon Engine
Perfect for real-time multiplayer games (turn-based or action). Unity-ready with fast integration.
Backendless / Nakama / Supabase (Open-source options)
Good if you want more control and flexibility. Great for custom game logic, matchmaking, and chat.