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JSON Serializers

JSON (JavaScript Object Notation) is the most interoperable serialization format, supported by virtually every programming language.

When to Use JSON

Choose JSON when: - Building public APIs requiring broad client compatibility - Configuration files humans need to edit - Debugging and logging (human readability valuable) - Web services where bandwidth is not the bottleneck - Cross-language data exchange required

Common Characteristics

Aspect Value
Human-readable Yes
Schema Optional (JSON Schema available)
Size 2-5× larger than binary
Circular references Not supported
Binary data Requires base64 encoding

C# JSON Serializers

Serializer Best For Speed Notes
SpanJson Maximum JSON speed ★★★★☆ UTF-8 focused, struct-based
Jil Fast, simple ★★★★☆ Sigil-based, limited maintenance
Utf8Json Fast, modern ★★★★☆ UTF-8 optimized
NetJSON Fast reflection ★★★★☆ No attributes needed
Json.NET Flexibility ★★★☆☆ Industry standard, feature-rich
MS DataContract Json WCF compatibility ★★★☆☆ Built-in
ServiceStack Json ServiceStack ecosystem ★★★☆☆ Integrated with framework
fastJson Speed claims ★★★☆☆ Verify with your data
SharpYaml YAML/JSON hybrid ★☆☆☆☆ YAML serializer with JSON support
YAXLib XML-focused ★☆☆☆☆ Primarily XML

Example: Json.NET

// Serialize
string json = JsonConvert.SerializeObject(person);

// Deserialize
Person person = JsonConvert.DeserializeObject<Person>(json);

Example: SpanJson

// Serialize to byte array (UTF-8)
byte[] json = JsonSerializer.Generic.Utf8.Serialize(person);

// Deserialize
Person person = JsonSerializer.Generic.Utf8.Deserialize<Person>(json);

Python JSON Serializers

Serializer Best For Speed Notes
orjson Maximum JSON speed ★★★★★ Rust-based, SIMD, fastest option
msgspec Speed + validation ★★★★☆ C-based, schema optional
rapidjson RFC compliance ★★★☆☆ C++ RapidJSON wrapper

Example: orjson

import orjson

# Serialize (returns bytes)
json_bytes = orjson.dumps(person)

# Deserialize
person = orjson.loads(json_bytes)

Example: msgspec

import msgspec

# Define schema (optional but recommended)
encoder = msgspec.json.Encoder()
decoder = msgspec.json.Decoder(Person)

# Serialize
json_bytes = encoder.encode(person)

# Deserialize with validation
person = decoder.decode(json_bytes)

Performance Comparison

Data Type C# Best (SpanJson) Python Best (orjson) Winner
Integer ~129K ops/sec ~488K ops/sec Python
SimpleObject ~34K ops/sec ~209K ops/sec Python
Person ~23K ops/sec ~60K ops/sec Python

Note: Python's orjson/msgspec significantly outperform C# JSON serializers due to highly optimized Rust/C implementations.

Type Handling

C# Type Support

Type Json.NET SpanJson Jil
POCOs ✓ ✓ ✓
Dictionaries ✓ ✓ ✓
DateTime ISO 8601 ISO 8601 ISO 8601
Enums As string/int As int As int
Nullable ✓ ✓ ✓
Polymorphism ✓ ✗ ✗

Python Type Support

Type orjson msgspec rapidjson
Dataclasses Via default Native Via default
Datetime Native Native Via hook
UUID Native ✗ ✗
Bytes Native ✗ Via hook
Numpy Native ✗ ✗

Security Considerations

  • JSON is safe — deserialization cannot execute arbitrary code
  • Validate input — schema validation prevents injection attacks
  • Size limits — protect against massive payloads causing OOM

Further Reading