MTPROTO, or Measurement & Traceability Protocol, is an open, vendor-neutral format for exchanging calibration certificates, measurement results and the traceability chains linking them. Maintained by the MTPROTO working group, it provides a compact, machine-readable record designed to be understood by laboratory information systems, test equipment and people. The format captures measurement values with units, uncertainty details and conditions, identifies reference standards and certificate records, and supports detached Ed25519 signatures for verification.

It is transport-agnostic and designed to preserve unknown fields for backward compatibility. The current stable release is version 1. 2, with JSON and CBOR identified as supported formats; a JSON Schema is also available.

The project provides a reference validator for checking records, canonical form and signatures, a core library for reading, writing and canonicalisation, and a preview tool for resolving traceability chains. The specification is licensed under CC BY 4. 0, while reference tooling is published under the MIT licence