Free Online Developer Tools
Format, validate, encode, hash and test code snippets — processed locally, so API keys and private data never leave your machine.
JSON Formatter
Beautify JSON with indentation and syntax error locations.
JSON Validator
Validate JSON and pinpoint the line and column of errors.
JSON Minifier
Minify JSON by removing whitespace.
HTML Formatter
Indent and beautify HTML markup.
HTML Minifier
Minify HTML by removing comments and extra whitespace.
CSS Minifier
Minify CSS to reduce stylesheet size.
CSS Formatter
Beautify minified CSS into readable rules.
JavaScript Minifier
Remove comments and whitespace from JavaScript safely.
JavaScript Beautifier
Re-indent minified or messy JavaScript.
URL Encoder
Percent-encode text for safe use in URLs and query strings.
URL Decoder
Decode percent-encoded URLs and inspect query parameters.
Base64 Encoder
Encode text or files to Base64 with full UTF-8 support.
Base64 Decoder
Decode Base64 to text, or download decoded bytes as a file.
UUID Generator
Generate random version-4 UUIDs in bulk.
Hash Generator
Generate MD5, SHA-1, SHA-256, SHA-384 and SHA-512 hashes.
Regex Tester
Test regular expressions with live match highlighting and groups.
Color Converter
Convert colours between HEX, RGB, HSL, HSV and CMYK.
HEX to RGB Converter
Convert HEX colour codes to RGB and RGBA values.
RGB to HEX Converter
Convert RGB values to HEX colour codes.
Unix Timestamp Converter
Convert Unix timestamps to dates and dates to timestamps.
HTML Entity Encoder
Escape special characters as HTML entities.
HTML Entity Decoder
Decode HTML entities back into readable characters.
SQL Formatter
Format SQL queries with keyword casing and indentation.
Markdown Previewer
Write Markdown and see a live, sanitised HTML preview.
Cron Expression Helper
Explain cron expressions in plain English and list next run times.
Why local processing matters for developers
Developers routinely paste JWTs, API responses, configuration files and customer data into online formatters. Many of those sites send the input to a server. These tools run entirely in your browser: JSON is parsed with the native JSON.parse, hashes use the Web Crypto API, and nothing is executed or uploaded.
Honest limitations
- The JavaScript minifier removes comments and whitespace safely but does not rename variables. For production builds, use a bundler such as esbuild or Terser.
- Formatters for HTML, CSS and SQL are pragmatic pretty-printers, not full parsers; unusual syntax may need manual tidying.
- Your code is treated as text — it is never run.
Guides for developer tools
All guidesHow to Format JSON Online (and Fix Common Errors)
How to pretty-print, validate and minify JSON, what the most common JSON syntax errors mean, and how to fix them quickly — with safe, local tools.
Read guideHow to Use Base64 Encoding (and When Not To)
What Base64 is, how it works, real uses like data URIs, email and API auth, why it is not encryption, and how to encode and decode text and files safely.
Read guideWhat Is JSON and Why Is It Used?
A beginner-friendly explanation of JSON: its syntax, data types, examples, how it compares with XML and CSV, and why APIs and apps use it everywhere.
Read guideDeveloper Tools FAQ
Is it safe to paste API keys or tokens?
The tools do not transmit input, but treat secrets carefully anyway: avoid pasting live production keys on shared computers, and rotate any key you suspect was exposed.
Does the regex tester use JavaScript regex syntax?
Yes. It uses your browser’s JavaScript RegExp engine, which differs slightly from PCRE (PHP) or Python in features like lookbehind support and flags.
Can I hash files?
Yes. The Hash Generator can compute MD5, SHA-1, SHA-256, SHA-384 and SHA-512 checksums of files up to 200 MB locally.
Other categories
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Finance, date, health and everyday calculators with clear formulas.
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Convert units, number systems, data sizes and time zones.
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Format captions, count characters, build UTM links and preview posts.
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Generate strong passwords and random strings with secure randomness.
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QR codes, barcodes, timers, clocks and browser information.
13 tools →