Do Source Generators in .NET 8/9 make a noticeable difference?

Yes, JSON source generators in .NET 8/9 make a dramatic difference in performance and app startup time. Source generators eliminate reflection completely by generating serialization code at compile time. This results in 3-5x faster serialization for complex types and near-zero startup overhead. Cold start times improve significantly in serverless environments where reflection metadata loading was a bottleneck. Trimmed app sizes are smaller since unused serialization code is removed. Native AOT compilation becomes viable with source generators, enabling faster deployment and execution. The generator analyzes types at build time, catching errors earlier. For high-performance APIs, source generators deliver measurable throughput improvements under load. .NET 9 enhances generators with better optimization and broader type support. Setup is simple: add [JsonSerializable] attribute to a context class. Test your JSON structures with our JSON Validator at jsonconsole.com/json-editor to ensure compatibility. For production .NET applications, source generators are essential for optimal performance and should be default choice.