Duper
The Format That's Super
Get picks like this daily. Today's launch numbers, the top launches, AI and tech news, and a daily opportunity pick, straight to your inbox.
Want to reach these readers? Sponsor an issue.
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.
HN · launched Nov 1, 2025 · 31 upvotes (top 24%) · 0 views
Niche: json tools and utilities · 64 launches, 3 in the last 7 days ▼ -40% · Explore this niche →
Category and tags
- Horizontal
Visit website ↗ Source listing ↗
More like this: all 64 launches in json tools and utilities →
Could you build this?
No Designing a reliable, zero-allocation/high-performance serialization format parser and serializer in Rust with Wasm and Python bindings requires formal grammar design and compiler engineering.
What it would actually take: Building a custom serialization spec and runtime requires writing a formal grammar (PEG or EBNF), designing an AST, and crafting a zero-copy, highly optimized recursive-descent or table-driven parser in Rust (e.g., using `nom` or `winnow`). It also requires extensive fuzz testing against malformed inputs, edge-case validation against IEEE 754 float quirks and unicode standards, plus FFI bindings via PyO3 and wasm-bindgen. This requires specialized programming language design and systems parsing expertise.
Discussion
15 comments analyzed.
Competitors mentioned: JSON5, YAML, TOML, XML, BAML
Concerns raised: Bundle size too large (488 kB uncompressed, 159 kB gzip) compared to native JSON, Performance cannot match runtime's native JSON.parse/stringify, Binary encoding less efficient than base64, Lacks formal grammar specification (BNF), DateTime support incomplete and ambiguous
Feature requests: Add comprehensive DateTime/ZonedDateTime support distinguishing Instant from ZonedDateTime, Provide formal BNF grammar specification, VS Code plugin/Prettier integration for authoring with auto-downlevel to JSON, Benchmarks comparing performance to native JSON, Optimize binary data encoding efficiency
Competitors
Other products that read as similar to this one : 426 launches clear the similarity bar, closest 8 shown.
Attention rank: #118 of 427 (itself plus its competitors, highest first, normalized so YC and Product Hunt are compared fairly).
Looks like the first mover among its competitors.
- ErisLint · github · 2026-09-18 · 18 upvotes · similarity 0.54
- json-const-content-mapper · github · 2026-10-21 · 12 upvotes · similarity 0.49
- JSON Formatter & Validator · ph · 2026-09-18 · 1 upvotes · similarity 0.48
- jsonfix · github · 2026-10-20 · 46 upvotes · similarity 0.47
- JSON Selection Formatter · ph · 2026-10-03 · 1 upvotes · similarity 0.47
- genpark-dynamic-json-schema-tool-synthesizer-skill · github · 2026-09-29 · 7 upvotes · similarity 0.45
- Ducklang: Achieving 100x more requests per second than NextJS · hn · 2026-01-01 · 9 upvotes · similarity 0.45
- JSON Formatter - Browser Tools · ph · 2026-09-25 · 2 upvotes · similarity 0.45
The niche, labels, vibe code rating and competitor comparison on this page are analysis by Nicheloom. If you use them, please credit nicheloom.com. How you may use our data.