Tracking code, errors & Core Web Vitals

These checks watch the technical health of a page as your visitors actually experience it. One keeps an eye on your analytics and marketing tags, one catches errors that break things inside the visitor's browser, and one measures Core Web Vitals from real visits. All of them run from a single small script you add to your site once.

What you need before you start

Unlike checks that TLDTrack runs from our own servers, these two watch the page inside your visitors' browsers, so they need a small piece of TLDTrack code on your site:

• The TLDTrack tracking snippet. A single lightweight script, tied to your site by a unique key, that you add to your pages once. One snippet powers error tracking, heatmaps, Core Web Vitals and the visitor feedback widget, so there is nothing extra to install for one versus another.
• The content-checks module switched on. The tag and error checks belong to that module, so if it is turned off in Settings their alerts are hidden. It is on by default.

Once the snippet is live, everything below happens automatically as real visitors load your pages.

Finding and installing the snippet

The snippet is generated for you, with the site's key already filled in. You can copy it from two places:

• The site's Heatmaps tab. With the Analytics module switched on, open the domain and go to its Heatmaps tab; the snippet is shown there ready to copy until the first page views arrive.
• The Error Tracking page. This lists every one of your sites with a copy button beside each, plus a status of Receiving data or Waiting for first visit, so you can see at a glance which sites are wired up and which are still waiting.

1. 1
   Copy the snippet for the site from its Heatmaps tab or from the Error Tracking page.
2. 2
   Paste it once, just before </head>, on every page of the site. On most platforms that means a shared header template, so it is one paste, not one per page.
3. 3
   That is it. The script loads asynchronously, so it does not slow the page down, and the site's status flips to Receiving data once the first visitor loads a page.

Tracking-code monitoring

Your website relies on small pieces of code, called tags, to measure and market your business. TLDTrack keeps an inventory of the tags it finds on your pages and tells you when that inventory changes. Common examples include:

• Google Analytics, which measures your traffic and behaviour.
• Google Tag Manager, which manages your other tags.
• A Meta pixel, which powers Facebook and Instagram advertising.

When a tag is added, removed, or its ID changes, you get an alert that names the specific tag, with its ID for Google tags such as Analytics, Tag Manager and Ads, for example that a particular Analytics ID was removed or swapped. That is how you catch a redesign or a plugin update that silently removed your conversion tracking, before weeks of data and ad measurement go missing. Tags that only load on some pages, or only after cookie consent, can show up as removed and then added again. When TLDTrack spots a tag it does not recognise, it works out what it is in the background so a newly-added tracker still gets named properly rather than reported as "something unknown".

Client-side error monitoring

Some faults never reach your server. A JavaScript error happens inside the visitor's own browser and can break a form, a booking step or a checkout while your server calmly reports that all is well. The snippet listens for these as real visitors trigger them, including uncaught script errors, failed promises, errors logged to the browser console, images, scripts and requests that fail to load, and not-found pages that mark themselves as one (WordPress does this by default). TLDTrack groups them so you are told about a genuinely new problem rather than the same error over and over, and the alert names the specific errors it saw so you know exactly where to look. You learn about the broken experience your customers are actually having, rather than waiting for one of them to give up and tell you, or simply leave.

Core Web Vitals from real visitors

The same snippet measures Core Web Vitals, Google's speed and stability metrics, from your actual visitors as they browse. If the snippet is installed, the numbers collect on their own. To see them, switch on the Analytics module; they appear in the domain's Heatmaps tab, in the Core Web Vitals (real visitors) section. Four metrics are tracked:

• LCP (Largest Contentful Paint): how long the main content takes to appear.
• INP (Interaction to Next Paint): how quickly the page responds when a visitor taps or clicks, measured as an approximation.
• CLS (Cumulative Layout Shift): how much the page jumps about while loading.
• TTFB (Time to First Byte): how quickly your server starts responding.

Each figure is the p75 over the last 30 days, meaning 75% of your visitors did at least this well, so one slow outlier cannot skew the picture. Results are split into mobile and desktop, because the two often tell very different stories, and each metric is banded Good, Needs work or Poor using the same thresholds as the lab PageSpeed check: LCP 2.5s and 4s, INP 200ms and 500ms, CLS 0.1 and 0.25, TTFB 800ms and 1800ms.

What you will see, and what to do

When something changes or breaks, you get an alert that names the specific item, a missing or swapped tag, or a particular error, so you are not left hunting. For a dropped or changed tag, check whether a recent site change or plugin update was responsible and put it right. For a client-side error, open the affected page and test the step that broke, since these often hide in a form or a checkout that looks fine until you try to use it. Because each item is muted for 7 days after you are first told, you will not be nagged about the same thing repeatedly, but a new or different item will still come through. For the full picture of how TLDTrack tells you about problems and who gets told, see alerts and notifications.

Setting it up, step by step

1. 1
   Open the website from your Domains list. If you have not added it yet, see Add your first website.
2. 2
   Copy the tracking snippet from the site's Heatmaps tab or the Error Tracking page, and paste it just before </head> on every page. It is a one-time install that powers all of these checks.
3. 3
   Make sure the content-checks module is on in Settings so the alerts come through.
4. 4
   When an alert names a tag change or an error you already expect, let the 7-day mute keep it quiet, or ignore a tag outright if you never want it flagged.

Where to set this up

Good to know

• Everything here runs from a single snippet you add once: error tracking, heatmaps, Core Web Vitals and the visitor feedback widget.
• The Error Tracking page lists every site with its snippet and a Receiving data or Waiting for first visit status. A site's Heatmaps tab also shows the snippet until the first page views arrive.
• Alerts name the exact tag or error involved, and each item is muted for 7 days after you are told so you are not nagged.
• Core Web Vitals are site-level p75 figures over the last 30 days, split mobile versus desktop, using the same Good, Needs work and Poor thresholds as the lab PageSpeed check.
• To watch the visible words and content on a page instead, see content checks.
• The tag and error checks belong to the content-checks module, so turning that module off in Settings hides their alerts for the whole team.