StacckApp

Free online JSON viewer, formatter, validator, parser and diff. Pretty-print, minify, sort keys, explore in a collapsible tree, and compare two JSON documents side-by-side — 100% in your browser.

Free online CSV viewer, parser and formatter. Auto-detects delimiter, browses rows in a table, validates and reformats — 100% in your browser.

Free online YAML viewer, parser and formatter. Validate, pretty-print, sort keys, and explore YAML in a collapsible tree — 100% in your browser.

Free online XML viewer, parser and formatter. Validate, pretty-print, minify, and explore XML in a collapsible tree — 100% in your browser.

Convert Excel files to CSV. All sheets supported. 100% client-side.

Paste or upload CSV → download as Excel .xlsx. Client-only.

Paste a JSON array → choose X and Y keys → render line/bar/pie. Download as PNG.

Free online Base64 text encoder and decoder. UTF-8 safe — works with emoji, Chinese, Arabic, anything. 100% in your browser.

Free online URL encoder and decoder. Percent-encodes spaces, special characters, and non-ASCII safely. 100% in your browser.

Free online HTML entity encoder and decoder. Convert <, >, &, ", ' to and from HTML entities. 100% in your browser.

Free online JWT decoder. Inspect the header, payload, and signature of any JSON Web Token. Decodes only — no signature verification. 100% in your browser.

Free online hash generator. Computes MD5, SHA-1, SHA-256, SHA-512 and HMAC-SHA-256 for any input. 100% in your browser using the Web Crypto API.

Free online number base converter. Edit any field — binary, octal, decimal, or hexadecimal — and see the others update live. 100% in your browser.

Drag any file to compute SHA-1, SHA-256, SHA-512 — 100% in your browser.

Convert text to and from binary, octal, hex. UTF-8 safe.

Classic shift cipher. Default shift 13 = ROT13. Encode and decode in one tool.

Convert any image to a Base64 data URL, or paste a data URL to preview and download the image. 100% in your browser.

Resize any image in your browser. Lock aspect ratio, choose dimensions, download as PNG/JPG/WebP. 100% client-side.

Convert images between PNG, JPG, and WebP in your browser. Adjust quality for lossy formats. 100% client-side.

Free online SVG optimizer powered by svgo. Removes comments, redundant attributes, and minifies markup. 100% in your browser.

Upload one image, get all favicon sizes you need: 16, 32, 48, 64, 180 (Apple touch), 192, 512 (PWA). 100% in your browser.

View EXIF metadata from any image. Download a stripped copy with metadata removed.

Crop any image with drag handles. Download as PNG. Client-side only.

Rotate any image: 90° steps or free angle. Download PNG.

Upload any image → see the N most-common colors as swatches with hex codes.

Create a professional invoice as a PDF — fill in your company info, client, and line items, then download. Free, no signup, 100% in your browser.

Build a clean, professional resume PDF in your browser. Fill in your details, download the PDF. Free, no signup.

Build a polished GitHub README in your browser. Fill in fields, copy the markdown. Free, no signup.

Build a cron expression with a visual UI and read a plain-English explanation. Supports standard 5-field syntax. 100% in your browser.

Generate a QR code for any text or URL. Adjustable size and error correction. Download as PNG. 100% in your browser.

Generate UUIDs in your browser. v4 (random) or v7 (timestamp-sortable). Copy individually or in bulk.

Generate strong, random passwords in your browser. Adjustable length and character classes. Never sent to a server.

Generate lorem ipsum placeholder text — by words, sentences, or paragraphs. Copy or download.

Pick your languages and frameworks, get a combined .gitignore. Templates for Node, Python, Go, Java, Rust, React, Next.js, macOS, Windows, and more. 100% in your browser.

Define an API response shape (fields + types) and generate N realistic fake records. Copy or download as JSON. 100% in your browser.

Build an Apache .htaccess file with toggles for HTTPS redirect, www handling, gzip, browser caching, custom 404, hotlink protection, and more. 100% in your browser.

Generate Nginx server-block configs with toggles for SSL, reverse proxy, static files, gzip, rate limiting, and security headers. 100% in your browser.

Test regular expressions against any text with live match highlighting and capture groups. JavaScript RegExp flavor. 100% in your browser.

Compare two pieces of text side by side. Shows line-by-line additions and deletions. 100% in your browser.

Convert text between camelCase, PascalCase, snake_case, kebab-case, CONSTANT_CASE, Sentence case, Title Case. 100% in your browser.

Turn any text into a clean URL slug. Lowercases, strips accents, replaces spaces and punctuation with hyphens. 100% in your browser.

Count words, characters (with/without spaces), lines, sentences, paragraphs, and bytes. Live as you type. 100% in your browser.

Convert Markdown to HTML in your browser. GitHub-flavored Markdown, live preview, copy or download the HTML.

Convert HTML to clean Markdown in your browser. Powered by Turndown.

Test JSONPath expressions live against any JSON. See matches as you type.

Validate JSON against a JSON Schema. See per-field errors with paths.

Decode UUID v1 and v7 to extract the embedded timestamp + node info. Works locally.

Split any URL into protocol, host, port, path, query, hash — with copy buttons.

Text to Morse and back. Audio playback included.

Paste tab or CSV data → render as a clean markdown or ASCII table. Adjustable alignment.

Two modes: text → big block letters, OR image → ASCII art (pixel luminance to chars).

Convert between Unix timestamps (seconds or milliseconds), ISO 8601 dates, and human-readable formats. Live, bidirectional.

Convert a date/time across multiple time zones at once. Powered by the browser's Intl API.

Convert colors between HEX, RGB, and HSL. Pick any color, copy any format. 100% in your browser.

Build CSS box-shadows visually. Live preview, copy the CSS. 100% in your browser.

Build CSS linear and radial gradients visually. Adjust stops, copy the CSS. 100% in your browser.

Write Mermaid diagrams (flowchart, sequence, class, gantt) → live SVG preview + download.

Upload an image → see how it looks with protanopia, deuteranopia, tritanopia, achromatopsia.

Visual editor for CSS cubic-bezier easing curves. Drag handles, copy the CSS string.

Visual clip-path editor: presets + custom polygon. Drag points, copy the CSS.

Visual CSS Grid builder: rows, columns, gap, named areas. Copy the CSS.

Visual flexbox builder: direction, justify, align, wrap, gap. Live preview + CSS.

Pick a base color → generate Tailwind-style 50-900 scale plus complement/triad/analogous.

Foreground + background colors → contrast ratio + WCAG AA/AAA pass/fail.

Generate tileable SVG patterns: dots, stripes, grid, waves. Adjust + download SVG.

A free in-browser playground for HTML, CSS, and JavaScript. Edit in three CodeMirror panels with a sandboxed live preview. Download as a single .html file. 100% client-side.

Run Python code right in your browser via Pyodide (CPython 3.x compiled to WebAssembly). Print, compute, and use the standard library — no install required. First run downloads ~10 MB (cached after).

Look up DNS records for any domain — A, AAAA, MX, TXT, CNAME, NS, SOA. Powered by Cloudflare DNS-over-HTTPS. 100% in your browser.

Look up geolocation, ISP, ASN, and timezone for any IP address. Shows your own IP by default. Powered by ipapi.co.

Modern WHOIS (RDAP) lookup for any domain. Returns registrar, status, dates, name servers. Powered by rdap.org.

Look up the PTR (reverse DNS) record for any IPv4 or IPv6 address. Powered by Cloudflare DoH.

Preview Open Graph and Twitter card previews from a URL fetch or pasted HTML and audit every meta tag for SEO and social sharing.

Monitor any URL — choose an interval, get alerted via Discord webhook or HTTP webhook when it goes down or recovers. Anonymous, no signup. Bookmark your monitor URL.

Paste a PEM-encoded public key (SPKI) to see its algorithm and key size. 100% in your browser.

Generate Apache .htpasswd lines using bcrypt. Works for nginx auth_basic too. 100% in your browser.

Generate the current 6-digit TOTP code from a base32 secret. Same algorithm as Google Authenticator. Live countdown. Local-only.

EFF wordlist passphrases — strong + memorable. Random via crypto.getRandomValues.

Check if a password appears in known breaches — using k-anonymity. Only the first 5 hex chars of SHA-1 leave your browser.

Split a bill with tip, per person. Instant.

Pick a birth date → see your exact age in years, months, days, plus days until your next birthday.

Pick two dates → see days, weeks, months, years between, plus business days (excluding weekends).

Three modes: X% of Y, X is what % of Y, percent change from X to Y.

Principal + rate + years → monthly payment, total interest, full amortization table (downloadable CSV).

Body Mass Index calculator — metric and imperial. Shows category instantly.

Convert between length, weight, temperature, area, volume, speed, and data. Live.

Generic loan: principal, rate, term → monthly payment + total interest fraction.

Principal + rate + years + compounding frequency → final value + total interest. Yearly breakdown.

Pick a base time + base TZ + multiple other TZs → render side-by-side. Plan global meetings instantly.

Split a PDF into individual pages or ranges. All client-side, no upload.

Combine multiple PDFs into one. Drag to reorder, then download.

Rotate any or all pages of a PDF. 0°/90°/180°/270°. All client-side.

Extract all text from a PDF. Copy or download as .txt. 100% in your browser.

Drop any .zip → browse contents, extract individual files. No upload to a server.