Performance and page speed

This article gives measured facts about the script, so you or your developer can judge its cost on your pages.

How it loads

• The install code adds one script tag with the async attribute. The browser keeps drawing your page while the script downloads.
• The script is a single file with no other libraries to fetch.
• On each page load it asks Tafsee once for your website's published campaigns, then decides in the browser when to show them.
• Events (shown, seen, closed, signed up) are sent in batches, not one request each.

Sizes

Measured on the build of 12 October 2026, compressed with gzip:

• The main script, loaded on every page: about 43 KB.
• The games part: about 11 KB. It is fetched only on pages that show a game, a moving background or an animated headline.
• The test panel: about 8 KB. It is fetched only when the page address carries ?tafsee-debug=1.

The build fails if the main script grows past its budget, so it cannot grow unnoticed.

What it does not do

• It sets no cookies.
• It does not change your page until a campaign shows. A popup is drawn in its own isolated part of the page (a shadow DOM), so its styles do not leak into your site and your site's styles do not leak into it.
• Errors inside the script are caught, so your page does not see them.

Things that do affect your page

• A top floating bar and a welcome mat push the page content down when they show.
• Pictures and videos you put in a popup are loaded from where they are hosted. Use pictures of a sensible size; uploads are limited to 1 MB each.
• The campaign's font is loaded when a campaign shows. If it cannot be loaded, the popup uses the device's own font.
• A popup that opens the moment the page opens competes with your own content for attention. A few seconds of delay is kinder; see Show when: the three questions.

Stop it on some pages

• To keep every campaign off a page, such as the checkout, add the path under Never show campaigns on these pages in Settings.
• A developer can stop automatic triggers on a page with TafseePopup.pause(). See JavaScript API.

If it does not work

• A speed test shows the script as slow: check that it is added once, not twice. See The install check fails.
• A strict Content-Security-Policy blocks it: allow scripts and requests from the host named in your install code.

Related

• Installing the code
• Privacy and data
• Styles clash, or another dialog is on the page