I built a JSON toolkit that never sends your data anywhere
Most "paste your JSON here" tools online send that JSON to a server to process it. For internal API responses, config files, or anything with real data in it, that's not something I wanted to do — so I built JSONLinter , a JSON toolkit where literally everything happens client-side. What it does It started as a validator/formatter, then grew into 42 tools across six categories: Validate & Format…
Most online tools that process JSON paste it into a server for processing. The author wanted to avoid this and built JSONLinter, a client-side JSON toolkit. It began as a validator/formatter, then expanded to 42 tools across six categories. The tools validate and format JSON, view and query it, convert it to various data formats, generate code, validate JSON against schemas, and encode data. There's also an optional AI assistant on the validation page, but it doesn't see the user's JSON or key.
The toolkit is built with React 19, TypeScript, Vite, Tailwind v4, and CodeMirror 6. The author faced challenges with prerendering without server-side rendering (SSR) and creating a structural JSON diff. They solved these by using Playwright to generate fully-rendered HTML for crawlers and comparing actual JSON structure instead of key order.
The selection highlighting issue was resolved by making the active-line background translucent. JSONLinter is available at jsonlinter.io, requiring no account or installation. The author seeks feedback on missing features compared to existing tools.
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