Xamarin.Forms
Xamarin.Forms was Microsoft's open-source (MIT-licensed) cross-platform XAML UI framework for building iOS, Android, and Windows apps from one shared C# codebase. Its final release, 5.0.0.2662, shipped March 25, 2024; Microsoft support ended May 1, 2024 for all Xamarin SDKs, and the GitHub repo was archived read-only that same day. The NuGet package logged 85.3M cumulative downloads before EOL. Microsoft's designated successor is .NET MAUI (v10.0.80 as of June 24, 2026, with MAUI 11 in preview), which replaces Xamarin.Forms' Renderer pattern with a Handler architecture -- the single biggest source of migration rework -- and collapses multi-project solutions into one SDK-style project. A CLI .NET Upgrade Assistant automates part of the port, but Microsoft's own docs warn most apps still need manual follow-up. Current version/status: 5.0.0.2662 (final release, Mar 25 2024) — EOL/unsupported since May 1, 2024. License: MIT. Maintained by Microsoft (discontinued; no longer maintained, GitHub repo archived read-only May 1, 2024).
Pick Xamarin.Forms only if you're stuck maintaining a legacy app you can't touch yet -- otherwise don't. It's dead: no security patches since May 2024, and every iOS/Android SDK bump since then is a compatibility roll of the dice. If you're starting fresh or actively modernizing, migrate to .NET MAUI (same C#/XAML skills, Microsoft's own upgrade path) unless you need pixel-identical custom UI across platforms, in which case Flutter's Skia/Impeller renderer beats MAUI's native-control approach. Microsoft's own migration docs admit the Renderer-to-Handler rewrite is "the most significant breaking change" -- there is no clean, automated 1:1 port, only a CLI assistant that gets you partway. Known weakness: Microsoft officially ended support on May 1, 2024, so the framework receives no security patches and breaks further with every new iOS/Android SDK release; Microsoft's own docs call the required Renderer-to-Handler rewrite for .NET MAUI migration "the most significant breaking change."