Free Online Developer Tools

All tools run 100% in your browser — no data is ever sent to a server. Fast, private, free.

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JSON to CSV Converter
Convert JSON arrays to clean CSV files instantly. Handles nested objects.
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JSON Formatter & Validator
Format, validate, and minify JSON. Instant syntax error detection.
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SQL Formatter
Format messy SQL queries. Supports SELECT, INSERT, UPDATE, CREATE and more.
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Cron Expression Generator
Build and explain cron schedules visually. See next 10 run times.
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JWT Decoder
Decode and inspect JWT tokens. View header, payload, expiry status.
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Epoch Timestamp Converter
Convert Unix timestamps to human-readable dates and back. Supports ms.
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Base64 Encoder / Decoder
Encode or decode Base64 strings. Supports URL-safe Base64 too.
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Regex Tester
Test regular expressions live. View matches, groups, and named captures.
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URL Encoder / Decoder
Encode or decode URL components. Handles percent-encoding.
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HTML Entity Encoder
Encode special characters to HTML entities and decode them back.
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Color Converter
Convert HEX, RGB, HSL, and HSV color formats instantly with a live preview.
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Hash Generator
Generate MD5, SHA-1, SHA-256, SHA-512 hashes from any text string.
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Text Diff Checker
Compare two text blocks side-by-side. Highlights added and removed lines.
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Markdown Preview
Write Markdown on the left, see the rendered HTML on the right in real time.
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UUID Generator
Generate UUID v1, v4 and ULID identifiers. Bulk generate up to 100.
100% Private. Every tool on this site runs entirely in your browser using JavaScript. No data is transmitted to any server. You can even save this page and use it offline.