Client-side tags are tracking scripts — like Google Analytics, Meta Pixel, or ad conversion tags — that load directly in a visitor’s browser when they land on your page. Each tag adds extra HTTP requests, external JavaScript files, and processing time.  The performance impact is real.

A website with 20-40 client-side tags (common in a busy GTM container) can add one to three seconds of load time.That directly hurts user experience, conversion rates, and Google search rankings.  Google’s Core Web Vitals measure things like Largest Contentful Paint (LCP) and Total Blocking Time (TBT) — both of which suffer when the browser is processing many scripts at once.
 

What to do:
Audit your tag setup regularly and remove tags you no longer use. Load non-essential scripts asynchronously so they do not block page rendering. Set smart triggers so tags only fire on pages where they are actually needed.  The best long-term fix is server-side tagging. Instead of loading many scripts in the browser, your site sends one lightweight event to a server, which then forwards data to all your tools. 

Seers.ai’s server-side tagging solution reduces browser-side script load significantly — improving your Core Web Vitals without sacrificing tracking accuracy.