HTML Compare Online - Diff HTML Code

Compare and diff two HTML documents. Fast, secure, and completely free. All processing happens in your browser — no data is sent to any server.

What is HTML Compare?

HTML Compare parses two HTML documents or fragments into their DOM tree structure and reports differences in elements, attributes, and text content — filtering out formatting noise like inconsistent indentation, attribute ordering, or whitespace between tags that a browser would ignore anyway. Two HTML snippets that render identically pixel-for-pixel can look wildly different as raw text if one was minified and the other wasn't; this tool compares what actually matters to the browser (and to a user), not incidental source formatting.

How to Use HTML Compare

1. Paste the original HTML into the left panel and the modified version into the right
2. The comparison runs as you type: both documents are re-indented the same way, then diffed side by side
3. Toggle whether attribute order and whitespace should be treated as significant
4. Read the result line by line: removed lines appear on the left, added lines on the right
5. Use the results to confirm a template or CMS output change is intentional

Key Features

• DOM-aware comparison that ignores insignificant whitespace and attribute ordering
• Highlights added, removed, and modified elements and attributes separately
• Handles both full documents and standalone HTML fragments
• Correctly compares text content independent of surrounding markup formatting
• Runs entirely client-side, without uploading page markup anywhere

Why Use HTML Compare?

Comparing two versions of rendered HTML output — before and after a CMS template change, a framework upgrade, or an A/B test variant — with a plain text diff mostly just shows you that whitespace and attribute order shifted, which tells you nothing useful. A DOM-aware comparison instead tells you precisely which elements were actually added, removed, or changed, which is the information you need when verifying a template change didn't introduce an unintended structural regression.

Common Use Cases

• Verifying a CMS template change only affected the intended part of the page
• Comparing rendered output before and after a frontend framework upgrade
• Confirming two A/B test variants differ only in the elements you intended to change
• Debugging unexpected markup differences between a staging and production build
• Reviewing changes to a reusable HTML email template

Frequently Asked Questions

Does it care about whitespace between tags, like indentation differences?

No — insignificant whitespace that a browser would collapse or ignore during rendering doesn't count as a difference; only meaningful structural and content changes are reported.

Does attribute order matter, like class before id versus id before class?

Not by default — attribute order has no effect on how a browser renders an element, so the comparison treats differently-ordered but identical attribute sets as equal.

Can it compare a full HTML document, including <head> content?

Yes, full documents compare correctly, including meta tags, scripts, and stylesheets referenced in the head.

Will it catch a change in inline CSS or JavaScript inside <style>/<script> tags?

Yes, the text content of those tags is compared like any other element's content, so changes inside embedded styles or scripts are flagged.

Is my HTML sent to a server to be compared?

No, all comparison logic runs locally in your browser's JavaScript engine.

Guides

• Comparing HTML: The Right Way (and Why Text Diffs Lie)

Related Tools

• Text Compare — Compare text and highlight differences
• XML Compare — Compare and diff two XML documents
• JSON Compare — Compare and diff two JSON objects