Free Online Developer Tools

Clean, fast, and privacy-friendly utilities for developers and webmasters. Every tool runs 100% in your browser — no sign-up, no uploads, no servers.

Data & Serialization

Work with JSON, CSV and encoded text — format, convert and validate without losing data to a third party.

JSON Formatter & Validator

Pretty-print, minify and validate JSON with clear error messages. Paste messy JSON and get clean, readable output in one click.

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JSON to CSV Converter

Convert a JSON array of objects into properly-escaped CSV — and convert CSV back to JSON. Handles nested fields and delimiters.

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Base64 Encode & Decode

Encode or decode text to and from Base64 instantly. Full UTF-8 support for Chinese, Japanese, emoji and other non-ASCII text.

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Text & Code

Inspect, compare and refine text and code with real-time feedback in your browser.

Regex Tester

Test JavaScript regular expressions in real time with live match highlighting, capture-group output and a quick syntax reference.

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Text Diff

Compare two blocks of text and see exactly what changed. Line-by-line diff with additions and removals highlighted, plus change stats.

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Web Dev & Security

Small utilities for everyday web development, debugging and hardening.

JWT Decoder

Decode a JSON Web Token's header and payload without sending it anywhere. Perfect for debugging auth tokens while developing.

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Epoch & Unix Timestamp Converter

Convert Unix timestamps to human-readable dates and back, in local and UTC time. Auto-detects seconds vs milliseconds.

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Password Generator

Generate strong, cryptographically-secure random passwords with full control over length, character sets and readability.

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Why use DevToolBox?

There are plenty of developer utilities scattered around the web, but most of them upload your data to a server, clutter the page with sign-up walls, or disappear overnight. DevToolBox is different:

  • Truly private. Every tool is plain JavaScript that runs on this page. Your JSON, tokens, passwords and code never leave your device.
  • Fast and dependency-free. No login, no accounts, no waiting. Open a tool and it works.
  • Made for real workflows. Each tool is focused, well documented and tested against the edge cases developers actually hit.
  • Free. Built to stay free. Advertising (if ever shown) only helps keep the servers that serve these pages running.

Bookmark the tools you use most, and check back — new utilities are added regularly.