Duper – The Format That's Super
An MIT-licensed human-friendly extension of JSON with quality-of-life improvements (comments, trailing commas, unquoted keys), extra types (tuples, bytes, raw strings), and semantic identifiers (think type annotations). Built in Rust, with bindings for Python and WebAssembly, as well as syntax highlighting in VSCode. I made it for those like me who hand-edit JSONs and want a breath of fresh air. It's at a good enough point that I felt like sharing it, but there's still plenty I wanna work on! Namely, I want to add (real) Node support, make a proper LSP with auto-formatting, and get it out…
In plain words
Duper is a human-friendly JSON extension that adds quality-of-life features like comments, trailing commas, and unquoted keys, plus extra types including tuples and bytes. Built in Rust with Python and WebAssembly bindings, it includes VSCode syntax highlighting. Designed for developers who hand-edit JSON files and want a more flexible format, Duper is available under an MIT license with planned improvements including Node support and an LSP with auto-formatting.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
An MIT-licensed human-friendly extension of JSON with quality-of-life improvements (comments, trailing commas, unquoted keys), extra types (tuples, bytes, raw strings), and semantic identifiers (think type annotations). Built in Rust, with bindings for Python and WebAssembly, as well as syntax highlighting in VSCode. I made it for those like me who hand-edit JSONs and want a breath of fresh air. It's at a good enough point that I felt like sharing it, but there's still plenty I wanna work on! Namely, I want to add (real) Node support, make a proper LSP with auto-formatting, and get it out there before I start thinking about stabilization.
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