Is System.Text.Json faster than Newtonsoft.Json in .NET 9?

Yes, System.Text.Json is significantly faster than Newtonsoft.Json in .NET 9, typically 2-3x faster for serialization and 1.5-2x faster for deserialization. System.Text.Json was built from the ground up for performance using Span<T> and modern .NET APIs. It allocates less memory and produces less garbage collection pressure. The performance gap widens with larger payloads and high-throughput scenarios. .NET 9 improvements include enhanced source generators that eliminate reflection overhead entirely. Newtonsoft.Json prioritizes features and flexibility over raw speed. For CPU-bound web APIs and microservices, System.Text.Json delivers measurable throughput improvements. Benchmarks show System.Text.Json processes JSON 2-5x faster depending on data complexity. However, Newtonsoft.Json remains faster for specific scenarios like dynamic types. Test your JSON structures with our JSON Formatter at jsonconsole.com before implementing. For new .NET projects prioritizing performance, System.Text.Json is the clear choice. Profile your actual workload to quantify benefits.