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Dev UtilitiesDeveloper tools · 2026

Developer tools that never send your data anywhere

JSON, colour, hashes and Base64 in one browser app. No server, in Russian and English, light and dark.

Open the app
Dev Utilities: a JSON document in the editor and its tree

The value you need is one query away

JSONPath under RFC 9535 shows the path, type and exact value of every match.

A JSONPath query and two matchesThe query $.endpoints[?@.p95Ms > 200].path and the paths it found

Types come straight from JSON

TypeScript, JSON Schema, YAML and CSV are built from the same document.

Converting JSON to TypeScriptTypeScript interfaces inferred from the document

The difference between versions becomes a patch

The comparison finds every change and saves it as a JSON Patch.

Comparing two versions: six changesA JSON Patch built from the changes

A palette is checked for readability at once

WCAG contrast is calculated for every colour pair, and scales are built in OKLCH.

Palette, tonal scale and contrast checkContrast of 5.35:1 with AA and AAA marks for text

A downloaded file is checked against its published sum

A whole sha256sum list is verified at once, and a mismatch stands out.

Three files, their SHA-256 sums and the list checkTwo sums match, one does not

How it is built

React 19 and TypeScript, no server.

Threads
Parsing, hashing and encoding run in Web Workers, so the interface never freezes.
Precision
Large numbers and decimals are never rounded.
Limits
JSON up to 5 MB, files for hashing up to 1 GB.
Base64
Files, Data URIs, hex view and JWT decoding.

Try it on your own data

Open the appAll work