GTM dataLayer checker
Check the size of a website dataLayer
Enter a URL to check whether a page uses a dataLayer, how large it is, and whether there are common tracking issues.
Scan results
The manual scanner is the accurate source of truth. The basic scan is a first pass based on page source that can be limited by browser security rules.
What this means
Size thresholds: under 50 KB is usually fine. 50 KB to 150 KB is worth reviewing. Over 150 KB may need attention. A large dataLayer can contribute to performance and tracking issues, depending on how it is used.
Technical details
Raw findings
Need an accurate live page scan?
Some React, Next.js and single page app websites create or change their dataLayer after the first page load. For the most accurate result, run the manual scanner on the page itself.
The snippet is safe and read only. It checks the current page, calculates UTF-8 byte size with TextEncoder, and copies a JSON report when clipboard access is available.