A heatmap shows you a colour. It does not name the section.

28 August 2026  ·  5 min read

Microsoft Clarity is free, unlimited, and good. If you are not using something like it, use it. This is about the one thing the format cannot do, and what that costs when a client asks you a direct question.

A scroll heatmap renders a page screenshot with a colour gradient over it: warm where people stayed, cold where they did not. A click map does the same for clicks. Both are honest, immediate, and require no interpretation to look at.

The interpretation comes afterwards, and that is where the work is.

Pixels are not sections

A heatmap is anchored to coordinates on a rendering of the page. Every question you actually want to ask is about a piece of content.

For one page, that is fine. It is a pleasant ten minutes. The trouble arrives at scale:

• Across many pages. Forty pages means forty screenshots to read. There is no ranking, because there is no number to sort by.
• Across screen sizes. The phone map and the desktop map are different pictures of different layouts. The same section sits in two places, and you compare them by eye.
• Across time. Edit the page and the screenshot changes. Last month’s map is a picture of a page that no longer exists, so before-and-after is two images side by side and a judgement call.
• In a document. You can paste a heatmap into a client report. You cannot write a sentence that says a specific section lost 46% of readers, because the map does not produce that sentence.

The question a client asks

The question is never “can I see the heatmap”. It is some version of:

“We paid for this page in March. Did it work?”

A heatmap answers that with a picture and a paragraph of your interpretation. That is a weaker answer than it sounds, not because the interpretation is wrong, but because it is yours. The client is being asked to trust a reading of a picture, at the exact moment they are deciding whether to fund more work.

A number attached to a named section is a different kind of answer. It survives being forwarded to someone who was not in the meeting.

Where the data goes

Worth knowing, separately from the format: a hosted heatmap tool works by sending visitor behaviour to the vendor’s servers. For Clarity that vendor is Microsoft, and the terms are what they are — free, in exchange for the data.

For most sites that trade is fine and nobody thinks about it. It stops being fine in two situations: a client in a regulated sector whose legal team reads the sub-processor list, and a public-sector or EU contract where “visitor behaviour is transmitted to a third country” is a question you have to answer in writing.

What to actually do

Not “replace your heatmap”. They answer different questions and cost different amounts:

• Keep the heatmap for exploration. When you do not yet know what is wrong with a page, a picture is the fastest way to form a hypothesis. Nothing beats it for that.
• Use per-section numbers for reporting and for comparison over time. Anything that has to be ranked, sorted, put in a document, or compared with last quarter needs to be a number attached to a thing that has a name.
• Decide before the project which one the client will be shown. Retrofitting evidence after a client asks whether the rebuild worked is how you end up defending a screenshot.