gem nosj is an extremely fast, json-gem-compatible JSON parser and generator for Ruby: Rust and SIMD via the first-party nosj crate, precompiled platform gems with per-platform PGO, partial parsing (JSON Pointer, single and batch), lazy documents that parse a value only when you touch it, file APIs that parse, generate, and query files natively (memory-mapped, so unread pages never leave the disk), allocation-free validation, document statistics from one counting pass, parse errors that carry line, column, and a caret snippet, a one-line JSON module drop-in, and a Rails mode that plugs into ActiveSupport's encoder seam.