msgspec is a fast serialization and validation library, with builtin support for JSON, MessagePack, YAML, and TOML. It features:

• 🚀 High performance encoders/decoders for common protocols. The JSON and MessagePack implementations regularly benchmark as the fastest options for Python.

• 🎉 Support for a wide variety of Python types. Additional types may be supported through extensions.

• 🔍 Zero-cost schema validation using familiar Python type annotations. In benchmarks msgspec decodes and validates JSON faster than orjson can decode it alone.

• ✨ A speedy Struct type for representing structured data. If you already use dataclasses or attrs, structs should feel familiar. However, they're 5-60x faster for common operations.

All of this is included in a lightweight library with no required dependencies.

msgspec may be used for serialization alone, as a faster JSON or MessagePack library. For the greatest benefit though, we recommend using msgspec to handle the full serialization & validation workflow:

Define your message schemas using standard Python type annotations.

>>> import msgspec >>> class User(msgspec.Struct): ... """A new type describing a User""" ... name: str ... groups: set[str] = set() ... email: str | None = None

Encode messages as JSON, or one of the many other supported protocols.

>>> alice = User("alice", groups={"admin", "engineering"}) >>> alice User(name='alice', groups={"admin", "engineering"}, email=None) >>> msg = msgspec.json.encode(alice) >>> msg b'{"name":"alice","groups":["admin","engineering"],"email":null}'

Decode messages back into Python objects, with optional schema validation.

>>> msgspec.json.decode(msg, type=User) User(name='alice', groups={"admin", "engineering"}, email=None) >>> msgspec.json.decode(b'{"name":"bob","groups":[123]}', type=User) Traceback (most recent call last): File "<stdin>", line 1, in <module> msgspec.ValidationError: Expected `str`, got `int` - at `$.groups[0]`

msgspec is designed to be as performant as possible, while retaining some of the nicities of validation libraries like pydantic. For supported types, encoding/decoding a message with msgspec can be ~10-80x faster than alternative libraries.

See the documentation for more information.

New BSD. See the License File.