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Developer Tools41 tools

Unix Time

Convert Unix timestamps to human-readable dates and vice versa easily.

JSON Editor

Format, beautify, and validate JSON data online with syntax highlighting.

Base64 Encode/Decode

Securely encode and decode strings to Base64 format right in your browser.

Character Count

Count characters, words, and lines in real-time with secure local-first processing.

URL Encoder/Decoder

Encode and decode URLs, making them safe for transmission and use in web addresses.

Random String Generator

Generate secure, random passwords and strings with customizable length and characters.

Faker Data

Generate realistic test data with multi-language support for development and testing.

JWT Debugger

Decode, verify, and debug JWTs (JSON Web Tokens) directly in your browser.

Data Converter

Convert between JSON, YAML, XML, CSV, and TOML formats instantly. Ideal for DevOps, legacy system integration, and data reporting.

PWA Asset Generator

Generate PWA icons and manifest.json from a single image. Create app assets instantly in your browser.

QR Code Generator

Create custom QR codes for URLs, WiFi, vCard, email, and SMS. Download as PNG or SVG instantly.

UUID Generator

Generate UUID v4, v7, ULID and NanoID in bulk, and inspect existing IDs.

Hash Generator

Compute MD5, SHA-1, SHA-256, SHA-512 and HMAC hashes for text or files.

Regex Tester

Test JavaScript regular expressions with live highlighting, groups and replace.

Cron Parser

Explain cron expressions in plain language and preview the next run times.

Text Diff

Compare two texts side by side and highlight added, removed and changed lines.

Color Converter

Convert colors between HEX, RGB, HSL, OKLCH, CMYK and check WCAG contrast.

HTML Entities

Encode special characters to HTML entities and decode them back.

Unit Converter

Convert length, weight, temperature, area, data and more, including Vietnamese and East Asian traditional units.

Password Generator

Generate strong random passwords with the Web Crypto API and check their strength.

Number Base Converter

Convert numbers between binary, octal, decimal, hex and any base from 2 to 36.

Code Formatter

Beautify or minify JavaScript, TypeScript, CSS, HTML, SQL, YAML and more.

Subnet Calculator

IPv4 and IPv6 CIDR calculator: network, broadcast, host range, mask and subnetting.

Timezone Converter

Convert a date and time across time zones with DST, offsets and working hours.

Markdown Preview

Write Markdown with a live preview, toolbar and HTML export.

Slug Generator

Turn titles into clean URL slugs, with Vietnamese, accent and Cyrillic support.

Case Converter

Convert text to camelCase, snake_case, kebab-case, Title Case and more.

What Is My IP

See your public IPv4 or IPv6 address, ISP, ASN and approximate location.

IP Lookup

Look up the country, city, ASN and network of any IPv4 or IPv6 address.

My User Agent

See and parse your user agent string and Client Hints, or analyse any UA.

HTTP Status Codes

Every HTTP status code from 100 to 511 explained, with search and filters.

Common Ports

Well-known TCP and UDP ports for SSH, HTTP, databases, mail and more.

MIME Types

File extension to MIME type list, plus a local file type checker.

Chmod Calculator

Convert Unix permissions between 755, rwxr-xr-x and chmod commands.

Image Compressor

Compress, resize and convert images to WebP, AVIF, JPG or PNG in your browser.

Contrast Checker

Check WCAG AA/AAA contrast between text and background colors, with fixes.

PX to REM

Convert px to rem and back, with a table and a CSS bulk converter.

JSON to TypeScript

Generate TypeScript interfaces, Go structs or Zod schemas from JSON.

Lorem Ipsum

Generate placeholder paragraphs, sentences or words, as text or HTML.

Keycode Tester

Press any key to see event.key, event.code, keyCode and modifiers.

ASCII Table

All 128 ASCII codes in decimal, hex, octal, binary and HTML entity.

Latest articles

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5 min read

px vs rem in CSS: When Each Unit Is the Right Choice

rem respects the user's font size setting, px does not. Learn what really changes between the two units, why zoom is not the whole story, and a practical rule for fonts, spacing, borders and media queries.

PX to REM
Read

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Browser & Device

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