json/home/releases/v3.12.0.md

v3.12.0

Released on 2025-04-11.

Fixes bugs found in 3.11.3 and adds several features. No public API was removed or renamed.

• Adds diagnostic byte positions via JSON_DIAGNOSTIC_POSITIONS, exposed through the new start_pos and end_pos member functions.
• Makes the conversion macros templated (so they also work with ordered_json) and adds NLOHMANN_DEFINE_DERIVED_TYPE for derived classes.
• Adds std::optional support (C++17) and lets patch, diff, and flatten work with arbitrary string types.
• Extends the binary formats: BJData draft 3 and unsigned 64-bit integers for BSON.
• Adds multidimensional C-array conversion and UTF-8 encoded std::filesystem::path conversions, and raises the minimum CMake version to 3.5 and supports CMake 4.0.

Full release notes.

API changes