SchemaLens Bookmarklet

Diff any SQL schema you see on the web — GitHub PRs, blog posts, docs, Stack Overflow — in one click.

👇 Drag this button to your bookmarks bar

Can't drag?

javascript:(function(){var t=window.getSelection?window.getSelection().toString():'';if(!t){var p=document.querySelectorAll('pre,code,.highlight,.blob-code-inner');for(var i=0;i<p.length;i++){if(/CREATE\s+TABLE/i.test(p[i].innerText)){t=p[i].innerText;break;}}}if(!t){alert('Select some SQL on the page first, or navigate to a page with CREATE TABLE statements.');return;}var u='https://schemalens.tech/app.html?schemaA='+encodeURIComponent(t)+'&ref=bookmarklet';window.open(u,'_blank');})();

How to Use

Drag the button above to your bookmarks bar.

On mobile, use the "Copy bookmarklet code" button and save it as a bookmark manually.

Go to any page with SQL.

GitHub PRs, migration blogs, documentation, Stack Overflow answers, etc.

Click the bookmarklet.

If you selected SQL text, it uses that. Otherwise it auto-finds the first CREATE TABLE block on the page.

SchemaLens opens with the SQL pre-loaded.

Paste your second schema and hit Compare. No copy-paste hunting required.

Perfect For

🐙 GitHub PR Reviews

Reviewing a migration PR? Click the bookmarklet on the "Files changed" tab to instantly diff the schema changes.

📚 Documentation & Blogs

Reading a tutorial with example schemas? Diff it against your own database in seconds.

💬 Stack Overflow

Someone posted a schema in their question? Open it in SchemaLens to understand the structure visually.

🔧 Migration Guides

Comparing before/after schemas in a migration guide? The bookmarklet grabs the first schema; you paste the second.

Demo

Imagine you're reading a GitHub PR with this schema change:

CREATE TABLE users (
  id SERIAL PRIMARY KEY,
  name VARCHAR(255) NOT NULL,
  email VARCHAR(255) UNIQUE NOT NULL,
  created_at TIMESTAMP DEFAULT NOW()
);
        

Click the bookmarklet → SchemaLens opens with this SQL already loaded → You paste your current schema → Instant diff + migration script.

Privacy

The bookmarklet runs entirely in your browser. It never sends data to any server — it simply opens SchemaLens with the SQL encoded in the URL. The schema data is processed client-side, just like the main app.

Chrome Extension

Want even more power? The SchemaLens Chrome Extension adds a "Diff in SchemaLens" button directly to GitHub PR pages — no bookmarklet needed.

Install Chrome Extension →