json-custom-numbers` is a conformant, performant, flexible custom JSON parser and stringifier for JavaScript. It's designed to parse large numbers from Postgres JSON values in a way that works around the limitations of native `JSON.parse()` implementations. The library offers several features, including support for non-recursive parsing, customizable number parsing, and an option to set a maximum depth limit for parsing or stringifying deeply nested structures. Overall, it's a useful tool for developers working with Postgres JSON values in JavaScript applications.