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DEVELOPER UTILITIES

Website Change Comparison

Releases, theme updates and plugin changes alter pages in ways no one checks: a canonical rewritten, a noindex left from staging, a heading removed. Comparing the page’s HTML before and after shows exactly which SEO elements changed.

Use the tool
How it works
  • Runs in your browser
  • Nothing you paste is uploaded
  • Free, no sign-up
Website Change ComparisonWhat it checks
  • CheckTitle, description, canonical, robots and language
  • CheckH1 and the heading outline
  • CheckStructured data types and hreflang
  • CheckLinks added and removed
Runs in your browser · nothing is uploaded

Free

no sign-up, no usage limit

0 uploads

what you paste stays on your device

5 checks

what the tool looks at

Offline

works once the page has loaded

Tool How to use it What it checks FAQ

Loading the tool…

HOW IT WORKS

How to use the Website Change Comparison

Two versions of a page’s HTML, pasted.

01

Save the page source before the change (Ctrl+U, then copy).

02

After the change, copy the source again.

03

Paste both and review every change, problems first.

WHAT IT CHECKS

What it looks at, and how to read it.

A table of changed elements, links added and removed, word and image counts, and problems such as a new noindex.

Checks

What it checks

  • Title, description, canonical, robots and language
  • H1 and the heading outline
  • Structured data types and hreflang
  • Links added and removed
  • Word and image counts

Results

How to read the results

  • Canonical and noindex changes alter indexing; treat them as release blockers until confirmed.

The concepts behind it, in the SEO glossary: Duplicate content.

GOOD TO KNOW

Common mistakes, an example and the limits.

Mistakes

Common mistakes

  • Launching a redesign that drops the category text block from every listing page.

Example

A worked example

After a theme update, the example page’s canonical points to the homepage and a noindex has appeared.

Limits

Limitations

  • Compares the HTML you paste; it does not fetch or render pages.
  • Text changes are counted in words, not shown line by line.

KEEP EXPLORING

Related free tools

Tools that pick up where this one stops.

On-Page SEO

HTML Content Extractor

Paste page HTML and pull out its title, meta tags, headings, links with anchor text, images and visible text.

Open HTML Content Extractor

Developer Utilities

HTML-to-Text Cleaner

Turn HTML into clean text or Markdown: scripts and styles removed, headings, lists and links kept.

Open HTML-to-Text Cleaner

Structured Data

JSON-LD Validator

Validate JSON-LD syntax, @context and @type, list every entity and check the properties Google requires for common rich results.

Open JSON-LD Validator

FAQ

Questions about the Website Change Comparison

Straight answers about what it does and where its limits are.

Can it compare two live URLs?

Paste their sources. Keeping both copies also gives you a record of what the page was.

Need this for a whole website, over time?

The NdovuSEOLabs platform connects your own Search Console, analytics and server logs, and audits every page on a schedule.

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