Online Visual HTML Comparator: Compare Two Pages Pixel by Pixel
When you modify CSS or update a component, how do you verify nothing else shifted? Classic diff tools compare source code line by line — but a CSS change can be invisible in code and catastrophic on screen.
Delta-QA offers a free visual HTML comparator that takes a different approach: it renders both versions in a real Chromium browser and compares the result pixel by pixel. What matters isn't what changed in the code — it's what changed on screen.
Text diff vs visual diff
A text diff tells you line 247 of your CSS file changed. It shows margin-left: 16px replaced by margin-left: 12px. Useful for code review, but it doesn't answer the real question: did this change break something visually?
A visual diff answers that question directly. It renders both versions, overlays them, and highlights every visible difference. Especially useful when a CSS change has cascade effects — modifying padding on a parent can shift all children. The text diff shows one changed line. The visual diff shows the real impact across the entire page.
How the Delta-QA comparator works
Step 1 — Enter your sources. Paste HTML directly or enter two URLs. URL mode loads pages in a real headless Chromium browser.
Step 2 — Automatic rendering and analysis. The comparator renders each version, extracts DOM and screenshots of each element, then runs a 5-pass structural matching algorithm.
Step 3 — Visualize differences. Results display side-by-side with modified elements highlighted. Each difference includes a strength score (0-100%).
Concrete use cases
Before deployment: compare staging vs production. After CSS updates: verify only intended changes are visible. Front-end code review: compare visually instead of imagining CSS impact. Cross-environment comparison. Redesign audit.
What it detects
The algorithm identifies 5 types of changes: added elements, removed elements, visually modified elements, moved elements, and moved-and-modified elements. Each with a strength score.
Why it's free
The online comparator is an acquisition tool. It lets anyone discover Delta-QA's visual comparison technology without installing anything. The desktop app goes further with journey recording, replay, multi-browser, and tracking over time.
FAQ
Does the online comparator require signup?
No. Entirely free, no registration. Paste HTML or enter URLs and compare immediately.
What's the difference between the online comparator and the desktop app?
The comparator does one-time comparisons. The desktop app adds journey recording, automatic replay, baseline tracking, and multi-browser support.
How many CSS categories does the comparator detect?
Over 38 categories: colors, typography, layout, borders, shadows, animations, responsive and more. Details on the Delta-QA detections page.
Try the Free HTML Comparator →
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