Free Developer Tools
Free online developer tools to format, generate, convert, validate, and debug. No sign-up, no server calls, no tracking. Just fast, reliable tools for everyday dev tasks.
Open-Source Tools
Standalone open-source packages available on GitHub and npm.
All Tools
Base64 Encoder/Decoder
Encode and decode text and files to Base64 with image preview support.
JWT Decoder
Decode JWT tokens into header, payload, and signature with expiration status.
Image to Base64
Convert images to Base64 data URIs, HTML tags, and CSS properties. Reverse mode included.
Encrypt / Decrypt
Encrypt and decrypt text with a passphrase using AES-256-GCM. Client-side authenticated encryption.
Hash Generator
Generate MD5, SHA-1, SHA-256, SHA-384, SHA-512 hashes for text and files.
JSON Formatter & Validator
Pretty-print, minify, and validate JSON with syntax highlighting and tree view.
JSON ↔ YAML Converter
Convert between JSON and YAML with live editing, syntax highlighting, and validation.
YAML Validator
Validate YAML with inline errors, tree view, and common template samples.
Markdown Preview
Live Markdown editor with GFM support, synchronized scrolling, and HTML export.
Text Diff
Compare two texts side-by-side or inline with character-level diff highlighting.
HTML ↔ Markdown
Convert between HTML and Markdown with configurable heading, list, and link styles.
Markdown to PDF
Convert Markdown to beautifully formatted PDF with custom fonts, colors, and layout.
Markdown to DOCX
Convert Markdown to Word documents with custom fonts, sizes, and formatting.
CSV Editor
Visual spreadsheet editor for CSV with sort, filter, search & replace, and export.
QR Code Generator
Generate QR codes for URLs, WiFi, vCards, phone, email, and SMS. Custom colors and error correction.
Barcode Generator
Generate Code 128, EAN-13, UPC-A, and more barcodes with customization options.
Image Converter
Convert images between PNG, JPEG, WebP, and more. Batch processing with quality and resize controls.
Favicon Generator
Generate favicons in all standard sizes from a single image. Get HTML link tags and web manifest JSON.
SVG Optimizer
Optimize and minify SVG files in your browser. Remove metadata, collapse whitespace, and see size savings.
Image Placeholder Generator
Generate placeholder images with custom size, colors, and text. Download as PNG or SVG.
Aspect Ratio Calculator
Calculate aspect ratios, resize dimensions proportionally, and visualize common ratios like 16:9 and 4:3.
Mesh Gradient Generator
Create beautiful mesh gradients with custom colors and positions. Export as CSS or PNG.
CSS Cover Art Generator
Generate abstract, geometric CSS-only cover art. Export as HTML/CSS or PNG image.
Color Converter
Convert between HEX, RGB, HSL, OKLCH. Contrast checker and palette generator.
Text to Gradient
Generate unique mesh gradients from any text. Same input always produces the same gradient. Export as CSS or PNG.
Bar Chart Race
Create animated bar chart race visualizations from CSV data. Watch categories compete and reorder over time.
Line Chart Race
Animated line chart that draws progressively over time. Also known as horserace or bump chart.
Bubble Chart Race
Animated bubble chart where circle sizes represent values. Watch bubbles grow and shrink over time.
Area Chart Race
Animated stacked area chart showing composition changes over time. Stacked and percentage modes.
DNS Lookup
Look up A, AAAA, MX, NS, TXT, CNAME, and SOA records for any domain.
CORS Tester
Check CORS headers and security headers for any URL. See if cross-origin requests are allowed.
SSL Certificate Checker
Check SSL/TLS certificate details for any domain. See expiry dates, issuer, SANs, and connection security.
OG Tag Validator
Validate Open Graph and Twitter Card meta tags. Preview how links appear on social platforms.
HTTP Status Codes
Complete HTTP status code reference with search. Click any code to copy. Grouped by category with descriptions.
Robots.txt Validator
Validate robots.txt syntax and test URL paths against crawl rules. Check which pages are allowed or blocked.
Sitemap Validator
Validate XML sitemaps for correct structure, URLs, dates, and priorities. Find errors and warnings instantly.
User Agent Parser
Parse any user agent string into browser, OS, engine, and device details. Auto-detects your current browser.
Regex Tester
Test regular expressions with live highlighting, capture groups, and quick-reference patterns.
Case Converter
Convert text between camelCase, snake_case, kebab-case, PascalCase, Title Case, and more.
Slug Generator
Generate clean, URL-safe slugs from any text. Customize separators, transliterate accents, and control length.
Word & Character Counter
Count words, characters, sentences, and paragraphs. Estimate reading and speaking time.
Copy Paste Characters
Click to copy special characters, symbols, arrows, math operators, Greek letters, and currency signs.
UUID Generator
Generate UUID v1, v4, and v7. Bulk generation with multiple output formats.
Password Generator
Generate strong passwords with customizable length, character sets, and strength meter.
Crontab Generator
Build and parse cron expressions visually. See next scheduled runs instantly.
Unix Timestamp Converter
Convert between Unix timestamps and human-readable dates with timezone support.
Built & Maintained by Varstatt
Varstatt is a one-person product studio run by Jurij Tokarski, product engineer since 2011. These tools are free and open — no signup, no catch.