JSONSchex - an implementation of the JSON Schema draft 2020-12 and latest specification for Elixir

Hello everyone!

I’d like to share JSONSchex, a JSON Schema Draft 2020-12 library for Elixir focused on correctness, repeated-validation performance, and practical OpenAPI workflows.

The basic idea: compile once, validate many times.

# Compile once.
{:ok, schema} =
  JSONSchex.compile(%{
    "type" => "array",
    "items" => %{"type" => "integer"}
  })

# Validate repeatedly.
:ok = JSONSchex.validate(schema, [1, 2, 3])
{:error, errors} = JSONSchex.validate(schema, [1, "oops"])

# Format structured errors when you need readable messages.
Enum.map(errors, &JSONSchex.format_error/1)

A few highlights:

• Draft 2020-12 supported in full, with 100% coverage from the official JSON Schema Test Suite.
• Designed for performance and simplicity, compile a schema once into an executable Schema struct, then validate data repeatedly with no repeated parsing overhead.
• Compile-time schemas using JSONSchex.Schema.compile!/2 or the ~X sigil.
• Structured errors with paths, failed rules, and context – not just a pass/fail result.
• Reference handling with configurable remote loaders, plus APIs to compile or bundle schemas embedded in larger documents, such as OpenAPI 3.*.

Recent work has focused on reducing repeated compilation, regex matching, and intermediate allocations. The repository includes benchmarks for some cross-library comparisons and JSONSchex before/after comparisons—results are workload-dependent, so I’d especially welcome real-world schemas to test against.

I hope this is helpful to you.

Thanks!