Free Developer Tools: JSON, JWT, Regex & SEO

Inspect data, debug formats and prepare code without setting up a project. Format JSON before converting it to TypeScript, inspect token payloads, test a regular expression or preview a search snippet.

JSONL / NDJSON Formatter & Validator

Validate and format JSON Lines (JSONL / NDJSON) data online — line-by-line error reporting, compact and pretty-print modes

ESM ↔ CommonJS Converter

Convert between ES modules and CommonJS syntax online

Semver Bump Calculator

Calculate major, minor, and patch version bumps for semantic versioning

Iframe Generator

Generate iframe HTML embed code with full attribute control — width, height, sandbox, referrer policy and more

JavaScript Key Code Tester

Press any key to inspect its JavaScript keyboard event properties: key, code, keyCode, and modifiers

YAML Formatter

Format, validate and minify YAML online. Fix YAML syntax errors instantly in your browser — no signup required.

Indent Converter

Convert between tabs and spaces and normalize code indentation

KeyCode Finder

Press any key to instantly see its JavaScript event properties: event.key, event.code, keyCode, and Unicode code point

SemVer Calculator

Check if a version satisfies a semantic versioning range — decode ^, ~, and comparison operators online

SVG to React Component

Convert SVG markup into a ready-to-use React component. Transforms class→className, kebab-case props→camelCase, and inline styles automatically.

JWT Decoder

Decode JSON Web Tokens securely in your browser

JWT Encoder

Create and sign JSON Web Tokens with custom payloads

JSON Formatter

Format, validate, and beautify JSON data

Regex Tester

Test and debug regular expressions in real-time

Diff Checker

Compare two texts and highlight the differences

Markdown Preview

Write and preview Markdown in real-time

Meta Tag Generator

Generate complete meta tags for SEO and social previews.

Website Speed Test

Check loading speed and core performance metrics for any URL.

Keyword Density Checker

Check keyword density to optimize your content for search engines

SERP Snippet Preview

Preview Google result snippets and validate title/meta description length.

Robots.txt Generator

Generate robots.txt rules to control crawling and include sitemap directives.

Canonical URL Checker

Validate canonical URLs and catch common indexing mistakes.

Hreflang Generator

Create hreflang tags for multilingual SEO and validate locale mappings.

UTM Link Builder

Build UTM tracking parameters for campaigns

CPF Validator

Check one or hundreds of Brazilian CPF numbers at once, with the reason each one fails.

CNPJ Validator

Validate numeric and alphanumeric CNPJs in bulk and see which check digit failed.

HTTP Status Codes Reference

Complete HTTP status codes reference with descriptions — search 60+ codes from 1xx to 5xx. Free and instant.

CSS Specificity Calculator

Calculate CSS selector specificity

Subresource Integrity Generator

Subresource Integrity Generator - Free online tool

YAML Validator

Free online YAML validator. Paste your YAML and instantly check syntax, see error line numbers, and preview parsed structure as JSON. No signup needed.

JSON Validator

Validate and format JSON online — instant syntax checking

Chmod Converter

Chmod Converter - Free online tool

Mic Test

Check your microphone in the browser: live level meter, waveform and playback

What Is My Screen Resolution?

See your screen resolution, viewport size and pixel ratio, live

Webcam Test

Check your camera in the browser: live preview, real resolution, FPS and snapshot

Choose by the task you need to finish

Validate JSON before generating TypeScript interfaces from the same sample.
Use the JWT decoder to inspect claims; decoding alone does not verify a signature.
Preview a page title and description before publishing; search engines may rewrite the displayed snippet.