Troubleshooting Missing Styles in Session Replay & Heatmaps

A troubleshooting guide for resolving missing layout, formatting, or visual styling problems in Sessions and Heatmaps.

Overview

If your session replay or heatmap appears without proper styling—such as broken layouts, missing fonts, or incomplete visual formatting—it is usually caused by inaccessible or blocked CSS files. 

Below, we’ve outlined the most common causes and the steps you can take to troubleshoot them.

Here are some of the most common reasons that this issue occurs:
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CSS files were renamed, removed, or deleted

The most common reason for your session replay and heatmaps to be missing styles is that Sigmize is unable to find the stylesheets on your server.

Sigmize works by storing the HTML and user behavior, but it does not store the styles or images used on your website. CSS and image files are loaded from your server during session playback, and if these files are no longer available, then your sessions will not appear as expected.

CSS files often become unavailable because their filename has changed. In most cases, your website platform will rename the CSS files every time you publish changes to the website. Sessions made before this change are still referencing the old filenames, and therefore, no styles will be loaded.

To resolve this issue, you can either keep the old stylesheets on your server(and contact us in support to link to a previously used stylesheet manually) or redirect requests from *.sigmize.com to a stable version.

Stylesheets are blocked by CORS or CSP

CSS files may also be unavailable because your web server blocks them from being loaded by Sigmize’s domain. If this is the case, you will typically see errors in your browser that directly mention Cross-Origin Resource Sharing (CORS) or Content Security Policy (CSP).

To resolve this, you must add *.sigmize.com to your CORS and CSP headers.

CSS requires authentication

Your web server may require authentication to load the CSS files. This typically occurs on websites that require visitors to log in before accessing a page. In the same way that the visitor must log in to view certain pages, they must also be logged in to load the CSS to their browser. 

You can work around this by logging in to your website in a separate browser tab and then viewing Sigmize’s sessions.