Free Online Developer Tools

A set of fast, focused developer tools that run entirely in your browser — no sign-up, no ads, and nothing is ever uploaded. Safe for private data, tokens, and code.

🔒 Every tool here runs 100% locally in your browser. Paste sensitive JSON, JWTs, or code freely — it never leaves your device.

Format & validate

JSON Viewer
Open & explore large JSON in a fast collapsible tree with search — without freezing.
JSON Formatter / Minifier
Beautify or minify JSON with one click, with syntax highlighting.
JSON String Escape / Unescape
Escape text for a JSON value, or unescape it back to plain text.
Validate JSON
Check JSON validity and find the exact error.
Fix JSON Errors
Common "Unexpected token" causes and how to fix each.

Convert

JSON → CSV
Turn an array of objects into a clean CSV for Excel or Sheets.
CSV → JSON
Parse CSV (quoted fields and all) into JSON, with safe type handling.
JSON → YAML
Convert JSON to YAML for config files — types preserved.
JSON → XML
Convert JSON to XML — objects to elements, arrays repeat, escaped.
JSON Flatten
Flatten nested JSON to dot-notation keys (a.b.c, list[0]).
JSON Sort Keys
Alphabetize JSON keys recursively for clean diffs.
JSON → TypeScript
Generate TypeScript interfaces from a JSON sample.
NDJSON ⇄ JSON
Convert between newline-delimited JSON and a JSON array.

Inspect & compare

JSONPath Tester
Evaluate JSONPath expressions against your JSON.
JSON Diff
Compare two JSON documents by structure — keys and values.
Text Diff Checker
Compare two texts or code blocks line by line.

Encode & decode

Base64 Encode / Decode
UTF-8-safe Base64, with a URL-safe option.
URL Encode / Decode
Percent-encode for URLs — component vs full-URL, side by side.
HTML Entity Encode / Decode
Escape HTML (< > & " ') or decode entities back to text.
JWT Decoder
Decode a JSON Web Token's header, payload, and expiry — locally.
Unix Timestamp Converter
Convert epoch ⇄ date; auto-detects seconds vs milliseconds.
SHA Hash Generator
SHA-256/1/384/512 hashes via your browser's crypto.
UUID Generator
Random UUID v4 / GUID values — bulk, with copy.

Text

Case Converter
camelCase, snake_case, kebab-case, CONSTANT_CASE and more.
Regex Tester
Test regular expressions live with highlighted matches and groups.
Word Counter
Words, characters, sentences, paragraphs, and reading time — live.
Lorem Ipsum Generator
Placeholder text by paragraphs, sentences, or words.