Performance Test – JSON serializers

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NOTE: For an updated set of benchmarks, see the Benchmarks page.

For those of you who have worked with JSON data in .Net you should be familiar with the DataContractJsonSerializer class and the JavaScriptSerializer class already. Both allow you to serialize/deserialize an object to and from a piece of string in JSON format, though there are some notable differences.

Besides these two BCL (base class library) JSON serializers, there are popular third-party offering such as Json.Net and a relatively newer ServiceStack.Text which also offers its own serialization format called JSV (JSON + CSV).

It is claimed that ServiceStack.Text‘s JSON serializer is 3x faster than Json.Net and 3.6x faster than the BCL JSON serializers! So, naturally, I had to test it out for myself and here’s what I found.

Assumptions/Conditions of tests

  1. code is compiled in release mode, with optimization options turned on
  2. 5 runs of the same test is performed, with the top and bottom results excluded, the remaining three results is then averaged
  3. 100,000 instances of type SimpleObject (see below) is created, each with a different ID and Name, and then given to the serializers to serialize and deserialize
  4. serialization/deserialization of the objects happen sequentially in a loop (no concurrency)
 1: [DataContract]
 2: public class SimpleObject
 3: {
 4:     [DataMember]
 5:     public int Id { get; set; }
 7:     [DataMember]
 8:     public string Name { get; set; }
 9: }


With these assumptions in mind, here are the average times (in milliseconds) I recorded for serialization and deserialization using each of five JSON serializers I tested:



Looking at these data, it would seem the ServiceStack.Text.JsonSerializer class offers the best speed in both serialization and deserialization cases, however the gains are much more modest than those advertised in the case of serialization. However, it really comes into its own when it comes to deserialization and the speed gains are quite impressive indeed!

Update 2011/09/12:

Turns out I had a typo in my performance test code and I was using Json.Net for the serialization test for SimpleJson, my bad, sorry folks… So I fixed the typo and ran the tests again and updated the data and graph above with the correct data. As Prabir Shrestha pointed out, by enabled Reflection.Emit you’re able to get much better performance out of SimpleJson and the new test results reflect this as the SimpleJson test was run whilst Reflection.Emit was enabled.

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