Paste your original HTML in the left panel and the updated version in the right panel, then click Find Differences. Added lines appear in green, removed in red. Upload .html, .htm, .xhtml, or .svg files directly. All processing runs in your browser - no code is sent to a server.
- All code is processed entirely in your browser - nothing is ever sent to a server.
- Supports .html, .htm, .xhtml, and .svg - any XML/HTML-like text file works.
- Attribute order matters in the diff even though browsers ignore it - use the same HTML formatter on both files to remove formatting noise before diffing.
- Source text only - visual changes from CSS or JavaScript are not detectable; only markup changes show.
- For stylesheet changes use Compare CSS; for JavaScript use Compare JavaScript.
How to use our HTML code comparison tool
Quickly compare HTML online by pasting or uploading your original HTML on the left and the changed version on the right. Click "Find Differences." The diff shows every added and removed line with line numbers. Toggle Unified or Side-by-Side view. The file upload dialog filters to .html, .htm, .xhtml, and .svg files.
Comparing HTML code explained simply
HTML is the skeleton of a web page - it defines what content exists and how it's organized, but not how it looks (that's CSS) or how it behaves (that's JavaScript). When you diff two HTML files, you're looking for changes to that skeleton: a heading that changed, a link that was updated, a <div> block that was added or removed.
The tricky part is that browsers are forgiving about HTML formatting in ways that a diff tool is not. <p class="intro" id="lead"> and <p id="lead" class="intro"> render identically in a browser - same element, same styles, same behavior. But in a line-by-line diff they appear as two different lines. So a diff showing many changed lines doesn't necessarily mean many visual changes; it may just mean a formatter reordered attributes.
Concrete example: an email newsletter with 47 lines. A copywriter updated the subject line, changed one button label, and updated a price. The diff shows exactly 3 changed lines. No need to re-read 47 lines to find what changed.
What to watch for when you compare HTML files
Attribute order in HTML tags
HTML attributes on a tag are compared as plain text per line. If a formatter reorders attributes - class before id vs after - the entire tag line appears changed even if the rendered output is identical.
When reviewing HTML output from two different static site generators building the same page, I regularly see every tag showing as changed because the generators emit attributes in different orders - href before class in one, reversed in the other.
Running both outputs through Prettier's HTML formatter before diffing collapses that noise completely, leaving only the actual content differences.
Self-closing and void elements in HTML
A change from <br> to <br /> (or vice versa) shows as a changed line. Both are valid HTML5, but the tool treats them as different strings. The same applies to <img>, <input>, <meta>, and other void elements.
Whitespace and indentation in HTML source
HTML is whitespace-insensitive in the browser, but the diff compares source text exactly. Reformatted HTML with different indentation shows many changed lines even if the document structure is unchanged. Format both files consistently before diffing for the cleanest output.
When to use an HTML diff checker
Email template versioning
Email HTML is often edited directly without version control. Comparing two versions of an email template shows exactly which elements, copy, or links changed - important for audit trails and for catching broken tags before sending to a large list.
Before any bulk email send, I compare the final template against the approved version from the creative brief. The diff either confirms they match, or shows exactly which lines changed during last-minute edits - usually a subject line update or a CTA link swap that didn't make it into the brief.
CMS template updates
When a CMS exports HTML for a page, comparing the exported HTML before and after an edit shows which parts of the template or content were modified.
Scraped page change detection
Compare two scraped versions of a webpage to detect changes in structure, content, or links since the last crawl. Useful for monitoring competitor pages or tracking changes to regulatory or government pages that publish important updates.
Accessibility audit verification
After adding ARIA attributes and roles to a page, compare the before and after HTML to confirm every targeted element received its aria-label, role, or tabindex - and that no existing attributes were accidentally removed in the process.
Schema markup and structured data changes
Compare two versions of a page to verify that JSON-LD script blocks were updated correctly. The diff immediately shows whether the schema type, property names, or values changed - without having to re-read the entire JSON block by hand.
Common mistakes when comparing HTML files
Comparing minified HTML against readable source
Minified HTML collapses everything to one or a few very long lines. Diffing minified against unminified shows the entire file as changed. Always compare files at the same format level - both prettified or both minified.
Comparing DevTools HTML against source files
HTML copied from the browser's DevTools Elements panel reflects the live DOM - it includes attributes injected by JavaScript, computed data- attributes, and framework-added classes that don't exist in the source file. Comparing live DOM output against a source template will show hundreds of false differences. Use the original source file on both sides.
Comparing template files without stripping template syntax
Files using Jinja {% %}, Handlebars {{ }}, or Django template tags contain template syntax mixed with HTML. If one version of a template has updated loop logic or conditionals, those lines appear in the diff alongside markup changes. The diff is valid, but expect a mix of template logic changes and HTML structure changes that require careful reading.
Comparing pages with dynamically injected content
If you scrape two HTML pages that contain timestamps, session tokens, or user-specific content, the diff shows those values as changed on every run even when the structure is identical. Strip or normalize dynamic values before diffing to isolate structural changes.
FAQs about comparing HTML code online
What does HTML stand for?
HTML stands for HyperText Markup Language. "HyperText" refers to links between documents - the defining feature of the web. "Markup Language" means the text is annotated with tags that describe content structure rather than appearance. HTML was invented by Tim Berners-Lee in 1991 and first standardized as HTML 2.0 by the IETF in 1995. The current standard, HTML5, was finalized by the W3C and WHATWG in 2014.
Can I compare SVG files?
Yes. SVG files are XML/HTML-like text. The file upload accepts .svg files and the diff compares the raw markup line by line.
Does this render the HTML?
No. The tool compares the raw source text. It does not open a browser context or compare visual rendering. If you change a color in an inline style, that line shows as changed. If you change a color only in an external stylesheet, nothing in the HTML diff changes.
Can I compare HTML template files (Jinja, Handlebars, Django)?
Yes. Template files use .html extensions and are plain text - the tool compares them line by line like any other file. Template tags (loops, conditionals, variable output) appear as plain text in the diff, so changes to template logic show up alongside HTML markup changes.
Can I compare HTML pasted from browser DevTools?
You can, but the results will include differences you didn't author. The browser's live DOM includes attributes injected by JavaScript, class names added by frameworks, and computed data- attributes. This can produce hundreds of apparent differences against a clean source file. Use the original source HTML on both sides for a clean comparison.
Is my HTML private?
Yes. All processing runs in your browser. No code is sent to any server.