Free Online Developer Tools
90+ fast, secure, and privacy-friendly tools that run entirely in your browser. No sign-up. No data sent to our servers.
All Tools
📦 JSON / Data
JSON Viewer
View, validate and explore JSON with syntax highlighting and interactive tree view
JSON Formatter
Format and beautify JSON with syntax highlighting and validation
CSV ↔ JSON Converter
Convert between CSV and JSON formats
JSON to TypeScript
Generate TypeScript interfaces from JSON objects
XML Viewer
Validate, format, and explore XML documents with an interactive collapsible tree view. Supports .xml, .xsd, .svg, .rss, .plist and any XML-based format. Runs entirely in your browser.
JSON Diff
Compare two JSON objects and visually highlight added, removed, and changed properties side by side.
JSON Schema Generator
Generate a JSON Schema (Draft 7 / 2020-12) automatically from a sample JSON object.
JSON to XML Converter
Convert JSON objects to well-formed XML and vice versa. Supports arrays, nested objects, attributes, and CDATA sections.
Fake Data Generator
Generate realistic fake data (names, emails, addresses, IBANs, phone numbers) in JSON, CSV, or SQL format.
🔐 Encode / Decode
Base64 Encoder/Decoder
Encode and decode Base64 strings online
JWT Decoder & Validator
Decode JSON Web Tokens (JWT) and inspect their header, payload, claims, and expiry status.
URL Encoder / Decoder
Encode or decode URLs and query string parameters using percent-encoding (RFC 3986).
Image to Base64
Convert images to Base64 encoded strings
Base64 to Image Decoder
Decode Base64 strings back to images. Preview the image live and download it as PNG, JPEG, or WebP.
HTML Entities Encoder
Encode and decode HTML entities
Base32 Encoder/Decoder
Encode and decode Base32 strings online
Unicode Inspector
Inspect Unicode characters and their properties
📝 Text
Word Counter
Count words, characters, sentences and paragraphs in text
Text to Speech
Convert any text to natural-sounding speech using your browser's Web Speech API. Select voice, language, rate, and pitch.
Case Converter
Convert text between different cases: uppercase, lowercase, title case, camelCase, snake_case
Text Summarizer
Summarize long articles, documents, or text into key sentences using extractive summarization. Runs entirely in your browser.
Slug Generator
Generate URL-friendly slugs from text
Text Diff
Compare two texts and highlight differences
Palindrome Checker
Check if a word, phrase, or sentence is a palindrome. Ignores spaces, punctuation, and case. Visual forward/backward display.
Anagram Generator
Generate all possible anagrams from a word or short phrase. Instant results for words up to 8 characters.
Text Reverser
Reverse any text — character by character, word order, or reverse each word individually. Instant preview.
ROT13 Cipher
Encode and decode text using ROT13 cipher
⚙️ Dev Utils
UUID Generator
Generate RFC 4122 compliant UUIDs (v1, v4, v5) in bulk. Export as JSON, CSV, or plain text.
Lorem Ipsum Generator
Generate Lorem Ipsum placeholder text in paragraphs, sentences, or words with optional HTML output.
QR Code Generator
Generate customizable QR codes for URLs, text, emails, WiFi, vCards, and phone numbers.
Regex Tester
Test, debug, and visualize regular expressions against sample text in real time with match highlighting.
Color Converter
Convert colors between HEX, RGB, HSL and HSV formats
JWT Generator
Generate and sign JSON Web Tokens (JWT) with custom header, payload, and secret. Supports HS256, HS384, HS512, RS256 algorithms.
SQL Formatter & Beautifier
Format and beautify SQL queries with proper indentation, keyword capitalization, and syntax highlighting.
Timestamp Converter
Convert between Unix timestamps and human-readable dates
CSS Minifier & Formatter
Minify CSS for production or beautify/format messy CSS for debugging. Shows size reduction statistics.
Markdown Preview
Live Markdown preview with instant HTML rendering. Supports CommonMark and GitHub Flavored Markdown (GFM): tables, task lists, strikethrough, and fenced code blocks with syntax highlighting. Copy generated HTML with one click.
Number Base Converter
Convert numbers between binary, octal, decimal and hexadecimal
Code Screenshot
Generate beautiful code screenshots with syntax highlighting, custom themes, and social-ready aspect ratios for Twitter, LinkedIn, and Instagram.
Cron Expression Builder
Build, validate, and explain cron expressions visually. See next run times and get plain English descriptions.
GraphQL Query Builder
Build, test, and explore GraphQL queries interactively with schema introspection and variable support.
OpenAPI / Swagger Viewer
Paste or upload an OpenAPI 2.0/3.x spec (YAML or JSON) and explore endpoints and schemas interactively.
🔒 Security
Hash Generator
Generate cryptographic hashes (MD5, SHA-1, SHA-256, SHA-512) from text or files instantly.
Password Generator
Generate strong, random passwords with custom options
Email Validator
Validate email addresses with syntax check, DNS MX record verification, and disposable email detection.
🌐 Network / API
DNS Lookup
Query DNS records (A, AAAA, MX, TXT, CNAME, NS, SOA) for any domain in real time.
IP Address Info
Get detailed information about any IP address: geolocation, ISP, ASN, reverse DNS, abuse contacts.
IP Subnet Calculator
Calculate IPv4 subnets, CIDR notation, network/broadcast addresses, and available host ranges. Supports VLSM and supernetting.
HTTP Headers Analyzer
Analyze HTTP headers from any URL
Curl to Code
Convert curl commands to code in multiple languages
📁 Files & Convert
PDF to Word Converter
Extract text from PDF files and download as a real Word document (.docx). Text-based PDFs only; runs entirely in your browser with no server upload.
Excel to CSV Converter
Convert Excel spreadsheets (XLSX/XLS) to CSV format. Supports multiple sheets, custom delimiter, and UTF-8 output.
CSV to Excel Converter
Convert CSV files to Excel spreadsheets (XLSX) directly in your browser. Auto-detects delimiter and infers column types.
Text to PDF Generator
Type or paste plain text and generate a printable PDF via your browser's print dialog. Choose A4/Letter, font size, margins, and line height. Plain text only — not a .docx converter.
PDF Compressor
Compress and reduce PDF file size online without losing quality. Adjust compression level.
Word to PDF Converter
Upload a .docx Word file and convert it to PDF directly in your browser. No server upload, no account required.
🎨 Design / Visual
Image Optimizer
Compress and optimize images (JPEG, PNG, WebP) directly in your browser. Adjust quality, resize dimensions, and convert formats — all client-side.
SVG to PNG Converter
Convert SVG graphics to high-quality PNG images with custom resolution and transparent background support.
Color Palette Extractor
Upload an image and extract its dominant color palette in HEX, RGB, and HSL formats.
CSS Gradient Generator
Create beautiful CSS gradients visually with live preview. Linear, radial, and conic gradients with unlimited color stops.
📊 SEO / Marketing
Keyword Extractor
Extract and rank the most relevant keywords from any text using TF-IDF scoring. Export as CSV or JSON.
Sitemap Generator
Generate XML sitemaps for your website automatically. Supports priority, changefreq, lastmod, and image/video sitemaps.
Backlink Checker
Analyze backlinks pointing to any URL. Check domain authority, anchor text distribution, and detect nofollow links.
SERP Preview Tool
Simulate and optimize how your page title, URL, and meta description appear in Google search results.
Meta Tags Preview
Preview how your page appears in Google search results, Facebook, Twitter/X, and LinkedIn sharing cards.
🔄 Converters
Markdown to HTML Converter
Convert Markdown to clean, valid HTML with live split preview, syntax highlighting, and GFM support.
HTML to Markdown Converter
Convert HTML to clean Markdown syntax. Supports tables, code blocks, lists, and links. Perfect for docs and static sites.
Text to Morse Code
Convert text to Morse code and back — with audio playback, adjustable WPM, and visual dot-dash display.
⇄ Data Converters
JSON to YAML Converter
Convert JSON objects to YAML format for configuration files, CI/CD pipelines, or scripts. Live preview, copy, and download.
YAML to JSON Converter
Convert YAML config files into JSON format quickly. Supports nested objects, arrays, multi-line strings, and all scalar types.
Markdown to PDF Converter
Convert Markdown documents to styled PDF directly in your browser. Print-ready output with code blocks, headings, and lists. No upload needed.
CSV to SQL Insert Generator
Convert CSV files into SQL INSERT statements. Configurable table name, dialect (MySQL/PostgreSQL/SQLite), and batch size.
HTML Table to CSV
Extract HTML tables and convert them to CSV format. Paste HTML and download CSV instantly. Ideal for scraping and data extraction.
🖼️ Image Tools
Image Resizer
Resize images to exact dimensions or by percentage. Lock aspect ratio, choose output format (PNG/JPEG/WebP), and download. All processing in your browser.
Image Format Converter
Convert images between PNG, JPEG, WebP, and BMP formats in your browser. Adjust quality for JPEG/WebP output. Instant preview and one-click download.
PNG to JPEG Converter
Convert PNG images to JPEG format with adjustable quality. Handles transparency by filling with a custom background color. Runs entirely in your browser.
JPEG to PNG Converter
Convert JPEG images to lossless PNG format directly in your browser. Supports JPEG, JPG, and JFIF files. Instant preview and download.
Image to Grayscale
Convert any image to grayscale (black and white) in your browser. Supports PNG, JPEG, WebP. Adjust brightness and contrast. Download result instantly.
🎨 Color Tools
Color Palette Generator
Generate harmonious color palettes from any base color. Choose complementary, triadic, analogous, split-complementary, or monochromatic schemes. Copy HEX, RGB, and HSL values.
Color Contrast Checker
Check WCAG 2.1 color contrast ratio between foreground and background colors. Shows AA/AAA pass/fail for normal and large text. Essential for accessible design.
CSS Shadow Generator
Generate CSS box-shadow and text-shadow visually with live preview. Adjust offset, blur, spread, color, and opacity. Copy ready-to-use CSS code.
Random Color Generator
Generate random colors with live preview. Lock individual channels, copy HEX/RGB/HSL values, and generate multiple colors at once for palettes.
HEX Color Validator
Validate HEX color codes instantly. Supports #RGB, #RGBA, #RRGGBB, and #RRGGBBAA formats. Shows color preview, RGB breakdown, and CSS-ready values.
⚡ Generators
.gitignore Generator
Generate .gitignore files for any language or framework. Select from Node, Python, Java, Go, Rust, React, Next.js, and more. Copy or download.
Favicon Generator
Generate favicons in multiple sizes (16×16, 32×32, 48×48, 64×64, 128×128) from any uploaded image. Download all sizes as individual PNGs.
README Generator
Generate a professional GitHub README.md with sections for description, badges, installation, usage, and contributing. Copy or download as .md.
License Generator
Generate open source license files: MIT, Apache 2.0, GPL 3.0, ISC, BSD 2-Clause, BSD 3-Clause, Unlicense. Copy or download as LICENSE.
SVG Placeholder Generator
Generate SVG placeholder images with custom size, background color, text color, and label. Copy as SVG code or data URL.
🧮 Calculators
Percentage Calculator
Three calculation modes: X% of Y, X is what % of Y, and % change between two numbers. Instant results with formula explanation.
Unit Converter
Convert between units of length, weight, temperature, speed, and area. Instant bidirectional conversion with common unit presets.
Aspect Ratio Calculator
Calculate and simplify aspect ratios from width and height. Scale dimensions while locking ratio. Common ratios reference table.
CSS Specificity Calculator
Calculate the specificity of any CSS selector. Breaks down IDs, classes, attributes, pseudo-classes, elements, and pseudo-elements. Compare two selectors.
Color Opacity Calculator
Pick a HEX color and an opacity level to get the equivalent rgba(), 8-digit hex (#RRGGBBAA), and CSS custom property. Live color swatch.
Why StackUtils?
We built this platform for developers who need reliable, lightweight tools without ads interrupting their workflow. Every tool works offline-capable and processes data directly in your browser.
⚡ Blazing Fast
Built on Next.js with zero-latency client-side processing. No waiting for server round-trips.
🔒 Privacy First
Your data never leaves your browser. We don't log, store, or analyze your inputs.
🆓 Always Free
All core tools are and will remain free. Supported by non-intrusive ads.
Your All-in-One Developer Toolkit
StackUtils is a free collection of over 90 browser-based utilities designed to save developers time every day. From formatting and validating JSON to generating UUIDs, decoding JWTs, converting between data formats, and previewing CSS effects — every tool is available instantly, with no account required and no data ever sent to our servers.
JSON & Data tools cover the full workflow: format, validate, diff, convert to XML, generate TypeScript interfaces, or build JSON Schemas. Whether you are debugging an API response or preparing data for a database, the right tool is one click away.
Text & code utilities include a markdown editor with live preview, a regex tester with match highlighting, a SQL formatter that supports multiple dialects, a word and character counter, and a full-featured case converter (camelCase, snake_case, kebab-case, and more).
Security & encode/decode tools let you encode and decode Base64 (with full UTF-8/emoji support), generate MD5, SHA-1, and SHA-256 hashes, create and decode JWT tokens, and generate secure random passwords with configurable complexity.
Network & API tools include a DNS record lookup, an HTTP response headers inspector, an IP geolocation tool, a subnet calculator, a cURL-to-code converter (for Python, JavaScript, PHP, and more), and an OpenAPI/Swagger viewer for exploring REST API specs directly in your browser.
Design & visual tools cover CSS gradient generation, QR code creation, color format conversion (HEX, RGB, HSL, HSV), color contrast checking for accessibility (WCAG AA/AAA), CSS box-shadow generation, and SVG to PNG conversion.
All tools are completely free, run client-side for maximum privacy, and are updated regularly based on community feedback. Bookmark stackutils.dev and you will never need to search for a developer utility again.