Dev Doctor — Free Online Developer Tools

Dev Doctor is a free suite of 40+ browser-based developer utilities for formatting, encoding, inspecting and converting data. Everything runs locally in your browser — no sign-up, no installation, and your input never leaves your device. The full list of tools available on the web:

Text & Data

JSON Formatter — Format and validate JSON.
JSON Editor — Visually edit JSON tree nodes.
Regex Tester — Test patterns with live match highlighting.
Hash Generator — Generate MD5, SHA-1, SHA-256 and more.
Diff Viewer — Compare two text blocks side by side.
Base64 / URL Encoder — Encode and decode Base64 and URLs.
Markdown Viewer — Render and preview Markdown.
JWT Tool — Decode tokens and sign new JWTs.
Number Base Converter — Convert between DEC, HEX, BIN and OCT.
URL Parser / Builder — Inspect and construct URLs.
String Case Converter — Convert between camelCase, snake_case and more.
HTML Entity Encoder — Encode and decode HTML entities.
Cron Parser — Parse cron expressions and preview upcoming runs.
Date Format Playground — Try date format patterns interactively.
XML Formatter — Format and pretty-print XML documents.
JSON to Kotlin — Generate Kotlin data classes from JSON.
Text Inspector — Character, word and line stats plus byte sizes.

Network

HTTP Request Tester — Send HTTP requests and inspect responses.
Certificate Viewer — Inspect X.509 PEM certificates.
WebSocket Tester — Connect and exchange WebSocket messages.

Design & Miscellaneous

Timestamp Converter — Convert Unix timestamps to readable dates.
Color Picker — Pick, convert and save colour swatches.
UUID Generator — Generate UUIDs and view history.
Color Contrast — Check WCAG AA/AAA contrast ratios.
Image to Base64 — Convert images to Base64 data URIs.
Font Scale Simulator — Preview text at system font scales 0.85x to 1.5x.
.env File Viewer — Parse .env files and mask sensitive values.
Asset DPI Preview — Preview asset rendering across Android densities.
Spacing Grid Overlay — Overlay an 8dp Material grid on any screenshot.

Android Developer Tools

These tools rely on Android platform features and run in the Dev Doctor Android app: dp / px Calculator, Permission Inspector, Deep Link Launcher, Device Info, ADB Wi-Fi Helper, Traffic Monitor, Logcat Filter, App Inspector, Crash Log Formatter, Intent Fuzzer and Mock Server.