Free online developer tools
Our free developer utilities run entirely in your browser. Format JSON, generate UUIDs, test regex patterns, encode Base64, and more — with no setup or login.
17 curated tools in this hub — open any card below, always free in your browser.
JSON Formatter
Format, validate, minify, and sort JSON instantly. Syntax highlighting, tree view, and error detection with line numbers.
UUID Generator
Generate v1 and v4 UUIDs instantly. Bulk generate up to 100 UUIDs, validate existing UUIDs, and download results as a text file.
Hash Generator
Generate MD5, SHA-1, SHA-256, SHA-384, and SHA-512 hashes from text or files. Verify file integrity with hash comparison.
Regex Tester
Test regular expressions online with real-time match highlighting, capture groups, replace mode, and a built-in regex cheat sheet.
Markdown Editor
Write and preview Markdown side by side. Export to HTML or .md file. Auto-saves your work. Full formatting toolbar included.
Markdown to HTML Converter
Convert Markdown to clean HTML instantly. Live preview, syntax highlighted output, full document mode, heading IDs, and file download.
HTML Formatter
Format, minify, and preview HTML in your browser — tidy tags and inspect structure for cleaner markup.
URL Encoder/Decoder
Encode URLs and query parameters with percent encoding or decode encoded URLs back to plain text. Also parses URL components.
Base64 Encoder/Decoder
Encode text and files to Base64 or decode Base64 back to text and files. Supports Unicode, URL-safe Base64, and file encoding.
Password Generator
Generate strong random passwords and secure passphrases instantly. Choose length, character types, and symbols. Runs entirely in your browser.
Username Generator
Generate memorable username ideas for games and social profiles — two-word styles, digit suffixes, random handles, and optional prefix or suffix.
Robots.txt Generator
Build a robots.txt with allow/disallow rules, crawl delays, and sitemap hints for SEO control.
Meta Tag Generator
Assemble Open Graph, Twitter Card, and classic meta tags for previews and search snippets.
Random Letter Generator
Draw random letters with optional alphabet filters for games, sampling, and test fixtures.
Random Password Generator
Create strong random passwords with adjustable length and character sets for accounts and API keys.
Number Sorter
Paste a list of numbers and sort ascending or descending—useful for datasets and quick QA.
Screen Resolution Checker
Instantly check your screen resolution, viewport size, device pixel ratio, and browser dimensions. Updates live when you resize.
Dev Tools — frequently asked questions
They are utilities developers use daily — JSON formatting, UUID and hash generation, regex testing, Markdown and HTML helpers, Base64 and URL encoding, robots.txt and meta tag drafts, and quick generators for passwords or usernames.
Explore related hubs
Jump to another Toolsle category hub — each directory targets free online tools keywords with its own crawlable landing page.
Browse directory
Full tools listing on the homepage
Prefer scanning everything in one grid? Continue from All tools on the homepage.