The dev toolbox
you've been looking for.

AWS VPC Subnet Calculator

Lay out public, private and database subnets across Availability Zones, with Terraform and CloudFormation output

CIDR to IP Range Converter

Turn CIDR blocks into first and last IP, usable hosts and address count, in bulk, with CSV export

CSP Checker

Paste a Content-Security-Policy or enter a URL to find unsafe-inline, wildcards and missing directives

Retry-After & Rate Limit Tester

Read 429 and 503 headers, test your client against a real rate limiter, and copy retry code with backoff

Request Headers & Proxy Test

See the exact headers a server receives from your browser, curl or code, and whether a proxy added its own

★ Featured

JSON Formatter

Format, validate and minify JSON instantly

JWT Generator

Create and sign JWTs with custom claims in-browser

Regex Tester

Test and debug regular expressions with live highlighting — and check them for Python, Java, .NET, Go and PHP

Diff Checker

Compare two texts and highlight differences

Color Palette Generator

Generate harmonious color palettes from any base color

AES / RSA Encryption

Encrypt and decrypt text using AES-GCM and RSA-OAEP

Format

JSON Formatter

Format, validate and minify JSON instantly

NDJSON / JSON Lines Formatter & Validator

Validate and pretty-print newline-delimited JSON, or convert to/from a regular JSON array

Markdown Preview

Write and preview Markdown in real time

SQL Formatter

Format or minify SQL across 14 dialects, including SQL Server, Oracle, and Snowflake

HTML Formatter

Prettify and minify HTML markup instantly

Word Counter

Count words, characters, sentences, and estimate reading time

SVG Optimizer

Strip editor cruft and shrink SVG file size — entirely in your browser

Image Compressor

Compress and resize JPEG, PNG, and WebP images entirely in your browser

Image EXIF Viewer & Remover

See exactly what metadata is embedded in a photo — camera info, timestamp, GPS location — and strip it before sharing

GraphQL Query Formatter

Format and minify GraphQL queries, mutations, and fragments

XML Formatter

Prettify, minify, and validate XML with CDATA-safe formatting

List Sorter & Deduplicator

Sort, dedupe, shuffle, and clean up lists of text lines

JavaScript / TypeScript Formatter & Minifier

Beautify or minify JS and TS code instantly — powered by Prettier and Terser

Encode

Base64 Encoder/Decoder

Encode or decode Base64 strings instantly

URL Encoder/Decoder

Encode and decode URLs and query parameters

JWT Decoder

Decode and inspect JWT tokens instantly

Hash Generator

Generate MD5, SHA-1, SHA-256, SHA-384 and SHA-512 hashes and HMACs

HTML Entity Encoder

Encode and decode HTML entities and special characters

Image to Base64

Convert images to Base64 data URIs for embedding

Base58 Encoder / Decoder

Encode or decode Base58 strings — the Bitcoin-style alphabet that skips ambiguous characters

Base32 Encoder / Decoder

Encode or decode RFC 4648 Base32 strings — the format behind TOTP secrets and DNSSEC

Base62 Encoder / Decoder

Encode or decode Base62 strings — the alphanumeric-only alphabet behind short URL slugs

Generate

Lorem Ipsum Generator

Generate placeholder text for your designs

Password Generator

Generate strong, random passwords with custom rules

UUID Generator

Generate RFC 4122 v4 UUIDs in bulk

ULID Generator

Generate sortable, URL-safe ULIDs in bulk — a 48-bit timestamp plus 80 bits of randomness

JSON to TypeScript

Generate TypeScript, Zod, Go, Python, Rust, C#, Kotlin or Swift types from JSON

JSON to Zod Schema Generator

Paste sample JSON and get a ready-to-use Zod schema plus its inferred TypeScript type

QR Code Generator

Generate QR codes from any URL or text

QR Code Scanner / Decoder

Upload a QR code image and decode exactly what it contains — including 2FA otpauth:// secrets

JWT Generator

Create and sign JWTs with custom claims in-browser

Git Command Generator

Find and copy git commands fast — search, filter by category, with warnings

Markdown Table Generator

Build Markdown tables visually — edit cells, align columns, export as HTML

Markdown Table of Contents Generator

Generate an anchor-linked table of contents from markdown headings — GitHub-style slugs

Meta Tags Generator

Generate Open Graph, Twitter Card, and SEO meta tags with live previews

Favicon Generator

Upload one image and get every favicon size your site needs

Fake Data Generator

Generate mock data from a field list or JSON Schema, as JSON, CSV or SQL for Postgres, MySQL and SQLite

.gitignore Generator

Pick your stack and get a ready-to-use .gitignore instantly

JSON Schema Generator

Infer a JSON Schema (draft-07) from a sample JSON object

Slug Generator

Turn titles into clean, URL-safe slugs — batch supported

robots.txt Generator

Build a robots.txt with per-bot rules, AI crawler blocking, and sitemap links

XML Sitemap Generator

Crawl your website, or paste its URLs, and get a ready-to-upload sitemap.xml

Barcode Generator

Generate EAN-13, UPC-A, EAN-8, Code 128, GS1-128, Code 39 and ITF-14 barcodes, one at a time or in bulk as a ZIP

README Badge Generator

Build shields.io badges for your README — custom text badges or live repo stats

Open Source License Generator

Pick a license, fill in your name, get a ready-to-commit LICENSE file

GitHub Actions Workflow Generator

Generate a hardened workflow with SHA-pinned actions, or audit one for security problems

MCP Config Generator & Validator

Build or check MCP server configs for Claude Code, Claude Desktop, Cursor, VS Code and Devin Desktop

Convert

Color Converter

Convert between HEX, RGB, and HSL color formats

Timestamp Converter

Convert Unix timestamps to dates in any time zone, with code for 12 languages incl. Temporal

Number Base Converter

Convert numbers between binary, octal, decimal, and hex

String Case Converter

Convert text between camelCase, snake_case, kebab-case and more

JSON ↔ YAML Converter

Convert between JSON and YAML formats instantly

IP / CIDR Calculator

Calculate subnet masks, IP ranges, and host counts from CIDR notation

CIDR Merge & IP Range to CIDR

Merge and deduplicate IP lists into the fewest CIDR blocks, subtract ranges, and convert IP ranges to CIDR

VLSM Subnet Planner

Split a network into subnets sized by host count — the most efficient CIDR for each, with AWS rules optional

AWS VPC Subnet Calculator

Lay out public, private and database subnets across Availability Zones, with Terraform and CloudFormation output

CIDR to IP Range Converter

Turn CIDR blocks into first and last IP, usable hosts and address count, in bulk, with CSV export

Docker Run to Compose

Convert docker run commands to docker-compose.yml and back

Dockerfile Generator

Pick a stack and get a sensible, multi-stage-aware Dockerfile — plus a matching .dockerignore

CSV to JSON Converter

Convert CSV to JSON instantly, or JSON back to CSV

XML ↔ JSON Converter

Convert between XML and JSON formats instantly, in either direction

Env File Tool

Parse, convert, and generate .env.example files from your .env

cURL to Code

Paste a curl command, get working code in Python, JavaScript, PHP, Go, Java, C#, Ruby, Rust, PowerShell and more

URL Parser & Query String Builder

Break down a URL into its parts and build query strings visually

.htaccess to Nginx Converter

Convert Apache .htaccess rules to nginx server block syntax

Meeting Planner

Rank the best meeting times across time zones with per-location working hours and a shareable link

JSON to Markdown Table

Convert a JSON array of objects into a ready-to-paste Markdown table

SVG to JSX / React Component

Paste raw SVG markup and get a ready-to-use React component

Database Connection String Parser & Builder

Parse a Postgres, MySQL, MongoDB, or Redis connection URI into its parts — or build one visually

Test

Regex Tester

Test and debug regular expressions with live highlighting — and check them for Python, Java, .NET, Go and PHP

Diff Checker

Compare two texts and highlight differences

CRON Expression Tester

Test cron for Linux, GitHub Actions, Kubernetes, AWS EventBridge, Quartz and Spring in any time zone

HTTP Request Builder

Build and send HTTP requests like a lightweight Postman

WebSocket Tester

Connect to any ws:// or wss:// endpoint, send messages, and watch a live, timestamped log

SemVer Calculator & Range Checker

Test versions against npm ranges like ^1.2.3 or ~2.0, compare versions, and preview version bumps

YAML / TOML / JSON Validator

Validate and convert between YAML, TOML, and JSON formats

Text Diff

Inline character-level diff between two short texts

XPath Tester

Test XPath expressions against XML and HTML with live results

CSS Selector ↔ XPath Converter

Convert between CSS selectors and XPath expressions for the common patterns both languages share

JSON Diff Checker

Compare two JSON objects and see exactly what changed, path by path

JSON Patch (RFC 6902) Generator & Applier

Diff two JSON documents into an applyable patch, or apply an existing patch to a document

IBAN Validator & Generator

Validate an IBAN's MOD-97 checksum, or generate a test IBAN for any supported country

Credit Card Test Number Generator

Generate Luhn-valid fake card numbers for testing payment forms, or validate a Luhn checksum

Payment Test Cards

Official test card numbers for Stripe, Adyen, Braintree, PayPal, Checkout.com and Square — success, declines and 3-D Secure

Unified Diff / Patch Generator & Viewer

Generate a real .patch file from two texts, apply one, or read one file by file, side by side

UUID Parser

Decode any UUID or ULID into its version, variant, and embedded timestamp

TypeScript 7 Migration Checker

Paste a tsconfig.json and see exactly which compiler options TypeScript 7 removes

Node.js Type-Stripping Checker

Scan a TypeScript file for syntax Node's built-in type stripping can't run directly

HTTP Header Inspector

Paste raw response headers and get a plain-English explanation of every one

Retry-After & Rate Limit Tester

Read 429 and 503 headers, test your client against a real rate limiter, and copy retry code with backoff

Request Headers & Proxy Test

See the exact headers a server receives from your browser, curl or code, and whether a proxy added its own

CORS Error Debugger

Walk through exactly why a cross-origin request would be blocked — or confirm it wouldn't be

JSONPath Tester

Test JSONPath expressions against JSON with live results and the exact path to each match

JSON Path Finder

Click any value in your JSON to get its path as JSONPath, JavaScript, jq or Python

User-Agent String Parser

Break a User-Agent header into browser, engine, OS, and device — with bot detection

Structured Output Schema Checker

Check a JSON Schema against OpenAI strict mode, Claude and Gemini structured outputs — and auto-fix it

Node.js 26 Upgrade Checker

Find what breaks on Node 26 LTS — removed APIs, deprecations, engines and native addons

Design

CSS Animations

Copy-paste CSS animations with live previews — tweak speed and easing, export to Tailwind v4

CSS Flexbox Generator

Build flex container and item properties visually, with a live preview and copy-ready CSS

CSS Grid Generator

Build a CSS grid layout visually — columns, rows, gaps, and per-cell spans

CSS clamp() / Fluid Typography Calculator

Build a fluid font-size that scales smoothly between a min and max viewport — no media queries

CSS Unit Converter

Convert between px, rem, em, pt, and % — with a configurable base font size

Aspect Ratio Calculator

Simplify a width/height into a ratio, or solve for a missing dimension given a ratio

SVG Path Visualizer

Paste a path d attribute and see it rendered live, with its bounding box and command breakdown

CSS Custom Properties Auditor

Paste CSS and find every --token, its usage count, duplicates, and unused or undefined variables

CSS Gradient Generator

Build linear, radial, and conic CSS gradients visually

Color Palette Generator

Generate harmonious color palettes from any base color

Mermaid Diagram Editor

Write flowcharts, sequence diagrams, and more as text — rendered live

Image Color Palette Extractor

Upload an image and extract its dominant colors as a usable palette

CSS Box Shadow Generator

Build single or multi-layer CSS box shadows visually, with live preview

CSS Specificity Calculator

Calculate and compare the specificity of CSS selectors

Placeholder Image Generator

Generate placeholder images with custom size, color, and text

CSS Scrollbar Generator

Style scrollbars with scrollbar-color/width, plus a WebKit fallback

CSS Scroll Carousel Generator

Build a zero-JavaScript carousel with dot navigation using ::scroll-marker and scroll-snap

Security

AES / RSA Encryption

Encrypt and decrypt text using AES-GCM and RSA-OAEP

CSP Header Builder & Analyzer

Build a Content-Security-Policy header visually, or paste one to check for unsafe directives

CSP Checker

Paste a Content-Security-Policy or enter a URL to find unsafe-inline, wildcards and missing directives

JWT Key Pair Generator

Generate RSA and ECDSA key pairs for signing JWTs — PEM and JWK formats

SSH Key Generator

Generate Ed25519 and RSA SSH key pairs in OpenSSH format, entirely in your browser

2FA Live Code & TOTP Generator

Paste a 2FA secret and get the live code — or several at once, one per line

HOTP Generator

Generate RFC 4226 counter-based one-time passwords — TOTP's time-independent sibling

2FA Backup Codes Generator

Generate one-time recovery codes for account 2FA setup, plus their SHA-256 hashes for server-side storage

package.json Script Inspector

See exactly which scripts run automatically on install, and which dependencies aren't pinned

HTTP Security Headers Checker

Check a URL or pasted headers against HSTS, CSP, X-Frame-Options and more, with HSTS preload status

JWK ↔ PEM Converter

Convert cryptographic keys between JWK and PEM formats

Secret / API Key Scanner

Paste code or a config file and find hardcoded API keys, tokens, and credentials before they reach git

Password Strength Checker

Check how strong a password actually is — entropy, common-password matches, and predictable patterns

JWK Thumbprint Calculator

Compute an RFC 7638 thumbprint for a JSON Web Key — the canonical fingerprint used as a stable kid

Passkey / WebAuthn Playground

Create a real passkey and run an authentication ceremony entirely in your browser — no server required

Bcrypt Hash Generator & Verifier

Hash a password with bcrypt, or verify a password against an existing hash — entirely in your browser

X.509 / PEM Certificate Decoder

Paste a PEM certificate or chain to see subject, issuer, expiry, SANs, key details, and fingerprints

SPF, DKIM & DMARC Checker

Check SPF lookups, DMARC policy and DKIM keys for any domain, and generate correct records

Google Authenticator Export Decoder

Decode Google Authenticator transfer QR codes into standard 2FA links for any authenticator app

Accessibility

Color Contrast Checker

Check WCAG AA/AAA contrast compliance between two colors

Accessibility

Color Blindness Simulator

Upload an image and see exactly how it looks under 7 types of color vision deficiency

Reference

HTTP Status Codes

Searchable reference for all HTTP status codes

Chmod Calculator

Calculate Unix file permissions with visual checkboxes

AI Token Counter & Cost Estimator

Estimate how many tokens your prompt costs, and what it'd run across Claude, GPT, and Gemini

LLM API Cost Calculator

Estimate your monthly Claude, GPT and Gemini API bill with prompt caching, batch and long-context pricing