About MessagePack ↔ JSON

Convert between MessagePack binary format and JSON. Part of the DevTools Surf developer suite. Browse more tools in the Data / SQL collection.

Use Cases

• Convert a JSON payload to MessagePack to estimate bandwidth savings for a high-frequency API.
• Inspect the decoded content of a MessagePack binary blob received from a service.
• Compare JSON and MessagePack sizes for a specific payload to justify a serialization format choice.
• Generate test MessagePack fixtures for integration tests against a service that uses it.

Tips

• Use MessagePack for internal service-to-service communication where both sides are under your control — it's not human-readable, so it's unsuitable as an external API format.
• Check the size comparison output — MessagePack is typically 20-50% smaller than JSON for the same data, with larger savings on numeric-heavy payloads.
• Verify that your target MessagePack library handles the ext type for custom types like dates — different libraries implement ext types incompatibly.

Fun Facts

• MessagePack was created by Sadayuki Furuhashi in 2010 specifically to solve JSON's verbose encoding problem while maintaining JSON's structural simplicity (maps, arrays, scalars).
• MessagePack integers use varint encoding — a 0 value takes 1 byte in MessagePack vs. 1 byte in JSON; but a 64-bit integer is 9 bytes in MessagePack vs. up to 20 bytes in JSON (ASCII decimal string).
• Fluentd, the CNCF-graduated log collector used in millions of Kubernetes deployments, uses MessagePack as its internal event format because it's 40% smaller and 3x faster to serialize than JSON.

FAQ

Is MessagePack compatible with JSON data types?

Yes — MessagePack supports the same data types as JSON (null, bool, int, float, string, array, map) plus binary data (bytes) which JSON cannot represent natively.

What's the size difference vs. JSON?

Typical savings are 20-50%. Integer-heavy data (event timestamps, sensor readings) saves the most. String-heavy data saves less because string encoding is similar in both formats.

Does it support the MessagePack ext type?

Ext types are decoded and shown as type code + raw bytes. Common ext interpretations (timestamps with type code -1, defined in the MessagePack spec) are decoded automatically.