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TOML version

Tomlyn v1 targets TOML 1.1.0 only. It does not support TOML 1.0 or earlier drafts.

See the official TOML v1.1.0 specification for the full language reference.

Target frameworks

Framework	Notes
net10.0	Fully optimized, all features available.
net8.0	Fully optimized, all features available.
netstandard2.0	Broad runtime compatibility; some newer numeric types (Half, Int128) unavailable.

Reflection, trimming, and NativeAOT

Tomlyn supports two metadata paths for object mapping:

Path	Description	Trimming/AOT safe
Source generation	TomlSerializerContext / TomlTypeInfo<T>	✅ Yes
Reflection	Automatic at runtime (enabled by default)	⚠️ Requires annotations

Disabling reflection

Reflection-based object mapping can be disabled before first use:

AppContext.SetSwitch("Tomlyn.TomlSerializer.IsReflectionEnabledByDefault", false);

When reflection is disabled:

• POCO/object mapping requires metadata via TomlTypeInfo<T> or TomlSerializerOptions.TypeInfoResolver.
• Built-in scalar converters and untyped containers (TomlTable, TomlArray) remain supported without reflection.

See Source generation and NativeAOT for details.

System.Text.Json interop

Tomlyn reuses System.Text.Json types in two areas:

• Naming policies - TomlSerializerOptions.PropertyNamingPolicy accepts any JsonNamingPolicy.
• Attributes - most common System.Text.Json.Serialization attributes work out of the box.
• Source generation - [JsonSerializable] roots and JsonKnownNamingPolicy are used for context declaration.