Free developer tools & website checks
Everyday dev tools that run entirely in your browser, with nothing uploaded, plus a few honest website security and compliance checks. No sign-up, no tracking, no email.
Genuinely free. No sign-up, no email, no limits, no cookies. We don't store the URL you analyse.
For designers and developers
Precision tools for daily use: exact calculations, all in the browser, nothing sent. Handy when you're handling code, tokens or secrets.
JSON to types
Paste JSON and get types in TypeScript, Go, Python, Rust, Kotlin and 11 more languages. The model you'd hand-write, in one click.
cURL to code
Paste a cURL command and get the code in fetch, axios, Python, Go or PHP. In the browser: tokens and keys are never sent.
Code formatter
Format JSON, JavaScript, TypeScript, CSS, HTML, Markdown and more with Prettier. Paste, format, copy: all in the browser.
JSON ⇄ CSV
Convert JSON to CSV and back, both directions, with commas and quotes handled properly.
JWT decoder
Decode a JSON Web Token's header and payload, with expiry and claims. In the browser: the token never leaves your device.
Base64 encode / decode
Encode and decode Base64 with UTF-8 and a URL-safe variant, right in the browser. No data sent.
Unix timestamp converter
From Unix timestamp to readable date and back, with seconds/milliseconds, UTC and local time.
WCAG contrast checker
The contrast ratio between two colours and WCAG AA/AAA compliance for text and UI. Normative formula, computed in real time in the browser.
Regex tester
Test regular expressions with match highlighting and captured groups, in real time.
Text compare (diff)
Compare two versions of a text line by line, with additions and removals highlighted.
SHA hash generator
SHA-1, SHA-256, SHA-384 and SHA-512 of a text, computed in the browser with Web Crypto.
URL encode / decode
Encode and decode URLs and parameters (percent-encoding), component or whole URL.
UUID v4 generator
Generate UUID v4 with cryptographic randomness, one or many at a time.
Cron explainer
Translate a cron expression into words and see its real next runs.
Case converter
Convert text to camelCase, PascalCase, snake_case, kebab-case, CONSTANT_CASE and more. Every variant at once.
Lorem ipsum generator
Placeholder text by paragraphs, sentences or words, with an optional classic opening. Ready to paste into mockups.
QR code generator
From text or a URL to a QR code, downloadable as PNG or SVG with a choice of error-correction level. All in the browser.
Security
Your business's site and email can be attacked by someone who's never seen them: automated scans don't pick their victims.
- Urgent
WordPress vulnerability (wp2shell)
In July 2026 a flaw emerged that lets an attacker take control of a WordPress site without a password. We check whether your version is among those affected.
Email security (SPF and DMARC)
Can someone send email pretending to be your company? We check whether your domain is protected against phishing in your name, and whether your own email risks spam.
What your site earns you
A slow or unreadable site loses customers before it has said a word.
Legal obligations
Accessibility, cookies and AI aren't good intentions: they're rules with penalties, and they apply to small businesses too.
AI Act transparency kit
From 2 August 2026 chatbots and AI-generated content have to be disclosed. Declare what you do and get notices, a statement and your duties with the correct dates.
Accessibility check
Does your site meet the standard the European Accessibility Act requires? A Lighthouse audit plus code-level checks.
Cookie banner check
Do Google Analytics or the Meta Pixel fire before consent? Analysis of the hints in the code: trackers, banners and prior blocking.
One more tool, Italian only
There's also an accessibility-statement generator, but it produces a statement on the Italian AgID template under Italian law, so it lives on the Italian tools page.
Why these tools are free
Merlin Tools runs on one rule: honest analysis that always declares what it cannot see, without collecting a single piece of data about you. None of these tools uses artificial intelligence. The checks are deterministic and verifiable, so the same site gives the same result every time. Every report copies with one click, in plain language: you can forward it to whoever manages your site and ask them about each point raised.