Comparison

How oneyaml-csharp compares with the .NET YAML libraries it is most often weighed against: YamlDotNet, SharpYaml and VYaml.

Bias. This page is written by the authors of oneyaml-csharp. We chose the criteria, and they are the ones this library was built for: YAML 1.2 behaviour, editing a file without disturbing it, and bounded handling of untrusted input. A project with other priorities would draw a different table. We tried to state each library's strengths as its own users would.

Versions. This page describes YamlDotNet 18.1.0, SharpYaml 3.14.0 and VYaml 1.4.0. Library facts come from the libraries' own documentation and from a survey we ran against those versions on 2026-09-30. On 2026-10-16 the current releases were YamlDotNet 18.1.0, SharpYaml 3.16.0 and VYaml 1.4.1; we read the release notes and READMEs of the newer two and found nothing that changes a line here, but we did not repeat the behaviour tests (depth limits, aliases) against them. Libraries change, so check the current release before you rely on a line here.

This page compares features and behaviour and has no figures. Speed and memory are in Performance, generated from the kit's release run, whose method line names the library versions it measured; these can be newer than the ones above. Conformance counts are in Conformance.

What each library is

Like with like

Compare libraries on the job they share.

• Typed load and dump. All four. oneyaml-csharp and SharpYaml share the System.Text.Json shape (options object, naming policies, System.Text.Json attributes, a source-generated context); YamlDotNet uses builders and its own attributes; VYaml generates code for [YamlObject] types. All four have a source generator for native AOT; YamlDotNet's is a separate package.
• Editing a file and keeping it as it was. oneyaml-csharp's YamlDocument writes a new value in the old one's style and keeps every other byte. SharpYaml's YamlSyntaxTree.WithTextChange also keeps every byte outside the range you replace, but you write the YAML text of the new value yourself. YamlDotNet's YamlStream and SharpYaml's model keep a scalar's style but lose comments and blank lines when they save. VYaml has no document model.
• Patching. oneyaml-csharp applies RFC 6902 and RFC 7396 to the YAML text, atomically. None of the others has a patch API; the usual route is to convert to a JSON tree (for example with Yaml2JsonNode and JsonPatch.Net), which loses formatting and comments.
• Limits on input. oneyaml-csharp bounds depth, alias expansion and integer size by default and has a YamlLimits.Untrusted preset (Limits). SharpYaml limits depth (64 by default) and refuses aliases into untyped targets unless you opt in. YamlDotNet's deserializer limits recursion; in our survey its YamlStream 18.1.0 had no depth limit, and VYaml had none either: deep input ended the process with a stack overflow.

Where oneyaml-csharp is the better fit

• You change YAML files that people also edit by hand, and the diff must hold only your change.
• You want to apply a JSON Patch or a merge patch to a YAML file and keep its comments.
• You want YAML 1.2 as the specification says, measured against the yaml-test-suite with every known deviation listed (Conformance).
• You read YAML from outside your program and want bounds on by default, with a stricter preset to opt into.
• You already know System.Text.Json and want the same options, attributes and source generation for YAML.

Where the others are the better fit

• You target .NET Framework, .NET Standard or Unity. oneyaml-csharp runs on .NET 8 and .NET 10 only. YamlDotNet and SharpYaml target netstandard2.0; VYaml is built for Unity.
• You need YamlDotNet's extension points. Type inspectors, node deserializers, event emitters and object-graph visitors let you change how YamlDotNet binds at a level the oneyaml-csharp serializer does not open. The YamlDotNet adapter does not provide them either, and the SharpYaml adapter has no custom converters; each migration guide lists what its adapter is missing.
• You want maturity and an ecosystem. YamlDotNet has years of production use, a large number of dependent packages and integrations (configuration providers, for example). oneyaml-csharp is new, and 1.0.0 is its first release.
• You read or write YAML 1.1 files as YAML 1.1. YamlDotNet reads yes as true and 017 as octal in typed binding by default. In oneyaml-csharp that takes the YamlDotNet adapter.
• You need comments as data. No library here gives a full comment API, but YamlDotNet's parser can report comment events and its emitter can write them. oneyaml-csharp keeps comments through edits but cannot read or add them.
• You need a streaming event parser. YamlDotNet's Parser, SharpYaml's parser and VYaml's YamlParser are public pull parsers. oneyaml-csharp exposes its reader only inside a converter.
• You need SharpYaml's schemas. SharpYaml can select the Failsafe, JSON, Core or an extended schema. oneyaml-csharp reads with the Core schema only.
• Speed on a given workload. See Performance for where oneyaml-csharp is slower; a library that wins on your workload may be the better choice.

Choosing

• New code on .NET 8 or later that reads configuration, or edits files people maintain: oneyaml-csharp.
• Existing YamlDotNet or SharpYaml code: keep it, or swap to the adapter and move to the OneYaml API file by file (from YamlDotNet, from SharpYaml).
• .NET Framework or Unity: YamlDotNet, SharpYaml or VYaml.