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/json-formatter before implementing. For new .NET projects prioritizing performance, System.Text.Json is the clear choice. Profile your actual workload to quantify benefits.