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Free Developer Tools — Formatters, Generators and Testers | LazyTools

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Free Developer Tools — Formatters, Generators and Testers

Free browser-based developer tools for formatting, testing, generating and debugging code.

Developer tools save time on repetitive tasks. From formatting JSON to generating cron expressions, these tools handle the small but frequent jobs that slow down development workflows. Furthermore, all tools run instantly in the browser with no setup.

Nothing is sent to any server. Your code, tokens and credentials stay entirely on your device. Moreover, no account is needed and no data is stored anywhere.

The collection covers five areas — code formatters, CSS and design tools, security and authentication, network and web, and testing and analysis. Additionally, use the search box or dropdown to find any tool quickly.

Code Formatters

Format, beautify and validate JSON, SQL, HTML, YAML and Markdown.

Data & Markup Formatters

JSON Formatter

Use the JSON Formatter tool for fast, accurate results in your browser. Additionally, no account or download is needed.

JSON Schema Validator

Use the JSON Schema Validator tool for fast, accurate results in your browser. Additionally, no account or download is needed.

JSON to CSV Converter

The JSON to CSV Converter flattens JSON arrays and objects into a CSV table with headers.

SQL Formatter

Use the SQL Formatter tool for fast, accurate results in your browser. Additionally, no account or download is needed.

HTML Beautifier & Minifier

Use the HTML Beautifier & Minifier tool for fast, accurate results in your browser. Additionally, no account or download is needed.

YAML Formatter

Use the YAML Formatter tool for fast, accurate results in your browser. Additionally, no account or download is needed.

Markdown to HTML

Use the Markdown to HTML tool for fast, accurate results in your browser. Additionally, no account or download is needed.

CSV Column Analyzer

The CSV Column Analyzer reads any CSV file and lists all column names, data types, row counts and sample values.

No matching tools found.

CSS & Design

Generate CSS for box shadows, flexbox, animations and colour contrast.

CSS Generators

CSS Box Shadow Generator

The CSS Box Shadow Generator generates SHA-256, SHA-512, SHA-1 and SHA-384 hashes for any text input in your browser usi

CSS Flexbox Generator

Use the CSS Flexbox tool for fast, accurate results in your browser. Additionally, no account or download is needed.

CSS Animation Generator

Use the CSS Animation tool for fast, accurate results in your browser. Additionally, no account or download is needed.

CSS Specificity Calculator

Use the CSS Specificity tool for fast, accurate results in your browser. Additionally, no account or download is needed.

CSS Units Converter

Use the CSS Units tool for fast, accurate results in your browser. Additionally, no account or download is needed.

Tailwind CSS Color Finder

The Tailwind CSS Color Finder lets you search Tailwind CSS colour classes by name, hex value or shade number.

Color Contrast Ratio Checker (WCAG live)

The Color Contrast Ratio Checker (WCAG live) measures colour contrast ratios and checks WCAG AA and AAA compliance for a

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Security & Authentication

Decode JWTs, generate bcrypt hashes and check password strength.

Auth & Security Tools

JWT Decoder

Use the JWT Decoder tool for fast, accurate results in your browser. Additionally, no account or download is needed.

JWT Generator

The JWT Generator creates and decodes JSON Web Tokens with custom headers, payloads and secrets.

Bcrypt Hash Generator & Verifier

The Bcrypt Hash Generator & Verifier generates SHA-256, SHA-512, SHA-1 and SHA-384 hashes for any text input in your bro

Password Strength Checker

Use the Password Strength tool for fast, accurate results in your browser. Additionally, no account or download is needed.

Checksum Calculator

Use the Checksum tool for fast, accurate results in your browser. Additionally, no account or download is needed.

HTML Entity Encoder

Use the HTML Entity Encoder tool for fast, accurate results in your browser. Additionally, no account or download is needed.

No matching tools found.

Network & Web

DNS lookup, IP subnet, URL tools and HTTP reference for web developers.

Network Tools

DNS Lookup Tool

The DNS Lookup Tool queries DNS records including A, AAAA, MX, CNAME, TXT and NS for any domain.

IP Subnet Calculator

Use the IP Subnet tool for fast, accurate results in your browser. Additionally, no account or download is needed.

URL Encoder/Decoder

Use the URL Encoder/Decoder tool for fast, accurate results in your browser. Additionally, no account or download is needed.

URL Cleaner & Tracker Remover

The URL Cleaner & Tracker Remover strips UTM parameters, affiliate trackers and other tracking tokens from URLs, leaving

User Agent Parser

Use the User Agent Parser tool for fast, accurate results in your browser. Additionally, no account or download is needed.

HTTP Status Code Reference

Use the HTTP Status Code Reference tool for fast, accurate results in your browser. Additionally, no account or download is needed.

Cron Expression Builder / Explainer

Use the Cron Expression Builder / Explainer tool for fast, accurate results in your browser. Additionally, no account or download is needed.

Robots.txt Generator

Use the Robots.txt tool for fast, accurate results in your browser. Additionally, no account or download is needed.

Sitemap Generator

Use the Sitemap tool for fast, accurate results in your browser. Additionally, no account or download is needed.

Meta Tag Generator

Use the Meta Tag tool for fast, accurate results in your browser. Additionally, no account or download is needed.

No matching tools found.

Testing & Analysis

Regex tester, viewport tester, page speed analyser and keyword density checker.

Testing Tools

Regex Tester

Use the Regex Tester tool for fast, accurate results in your browser. Additionally, no account or download is needed.

Viewport Tester

Use the Viewport Tester tool for fast, accurate results in your browser. Additionally, no account or download is needed.

Page Speed Analyser

Use the Page Speed Analyser tool for fast, accurate results in your browser. Additionally, no account or download is needed.

Keyword Density Checker

Use the Keyword Density tool for fast, accurate results in your browser. Additionally, no account or download is needed.

Screen & Device Info

Use the Screen & Device Info tool for fast, accurate results in your browser. Additionally, no account or download is needed.

Screenshot to HTML

Use the Screenshot to HTML tool for fast, accurate results in your browser. Additionally, no account or download is needed.

No matching tools found.

Developer Tools Tools for Everyone

Developer tools should be fast and frictionless. These tools open instantly and require no setup, login or installation. Furthermore, they work in any browser on any device, making them useful whether you are at a desk or checking something on the go.

Security-sensitive operations such as JWT decoding and bcrypt hashing all run locally in your browser. As a result, no sensitive tokens or credentials are ever transmitted to an external server.

All tools are mobile-friendly and work offline after the page loads. Moreover, the code formatters support JSON, SQL, HTML and YAML — covering the most common formatting needs in one place.

Common Questions

Yes, every tool is completely free. No account, subscription or API key is needed. Furthermore, all tools are available instantly in your browser.
No. JWT decoding happens entirely in your browser using JavaScript. As a result, your token is never transmitted anywhere. This is especially important for production tokens.
Yes, after the page loads, most tools work without an active internet connection. Furthermore, this is because all logic runs locally in your browser.
The regex tester uses JavaScript's built-in regex engine. Moreover, this covers the vast majority of common patterns. For PCRE-specific features, check a language-specific tool.
Yes, all developer tools are responsive. They work on phones, tablets and desktops. Furthermore, they run locally so performance is not affected by connection speed.