How do I check if GA4 is installed correctly?

View the page source and look for `gtag.js` and a measurement ID in the `G-XXXXXXXXXX` format. Then open DevTools, filter the Network tab for `collect` and reload the page: a correct install sends a request to `google-analytics.com/g/collect?v=2` with your measurement ID. Finally, confirm the event arrives in GA4 DebugView or the Realtime report.

How can I tell if GA4 is firing on every page?

You cannot tell from one page. The tag usually lives in a template, so it can be present on the homepage and missing on the checkout, the blog or a landing page built by a different team. Test at least one URL per template, and retest after every deploy.

Why does GA4 show no data even though the tag is on the page?

The most common causes are consent gating (the tag only loads after the cookie banner is accepted), a wrong or outdated measurement ID sending data to another property, a GTM container that loads without a published GA4 tag inside it, or a JavaScript error that stops the script before it runs.

Does Deltio alert me when the GA4 tag disappears?

Yes. Deltio checks the marketing tags on every URL in your sitemap and compares each scan with the previous one. If GA4 disappears from a page, appears somewhere new, or its measurement ID changes, you get an email and a Slack alert.

Which marketing tags can Deltio monitor?

GA4, Google Tag Manager, Meta Pixel, Hotjar, Microsoft Clarity, LinkedIn Insight Tag and TikTok Pixel. Deltio also detects the cookie banner or CMP on the homepage and tells you when the provider changes, which is a frequent cause of tags silently failing to load.

How much does Deltio cost?

Starter is £24 a month, or £20 a month if you pay annually. Professional is £49 a month and Enterprise is £119 a month. Every plan comes with a 14-day free trial.

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How to Check GA4 Is Actually Firing on Every Page

To check if GA4 is installed correctly, view the page source and look for gtag.js or a measurement ID shaped like G-XXXXXXXXXX, then open DevTools, filter the Network tab for collect and reload: a working install fires a request to google-analytics.com/g/collect?v=2. Confirm the hit reaches the property in GA4 DebugView or the Realtime report. One page proves nothing, though: the tag can sit on the homepage and be missing from the checkout, blocked behind a consent banner, or still pointing at an old measurement ID after a migration. Deltio monitors GA4, Google Tag Manager, Meta Pixel and the other marketing tags on every URL in your sitemap and alerts you when a tag vanishes or its ID changes, from £20 a month with a 14-day free trial.

Most GA4 installs get checked once, on the homepage, on launch day. Then a developer ships a new template, a consent platform gets swapped, and the tag quietly stops firing on half the pages. Nobody notices until a monthly report shows traffic that never existed.

Read the HTML source

The snippet: open view-source: on the page (Ctrl+U) and search for gtag.js. A standard install loads https://www.googletagmanager.com/gtag/js?id=G-XXXXXXXXXX.
The measurement ID: search for G-. It must match the ID in your property under Admin, Data streams. A mismatch means the data is going somewhere else.
Via Google Tag Manager: if you only see gtm.js?id=GTM-XXXXXXX, that proves GTM is on the page, not GA4. The container injects the tag at runtime, so the raw source cannot confirm it.

Watch the network request

The source shows the snippet is on the page. It does not show that the tag ran.

Open DevTools: F12, Network tab, tick Preserve log, reload.
Filter for collect: a correct install sends a request to google-analytics.com/g/collect?v=2&tid=G-XXXXXXXXXX&en=page_view. v=2 is the GA4 protocol, tid your measurement ID, en the event.
Nothing fires: the tag is dead there. Usual suspects: a consent script blocking it, your own ad blocker (retest in incognito with extensions off), or a JavaScript error earlier in the page.

Prove the data reaches the property

Tag Assistant: go to tagassistant.google.com, connect the URL and click through the site. It lists every tag found, its ID, and whether it fired.
DebugView and Realtime: with Tag Assistant connected, GA4 Admin, DebugView shows the events arriving live. Reports, Realtime confirms the same from a clean incognito window. Only these views prove the hit was accepted, not just sent.

What a one page check misses

Template gaps: the tag sits in the marketing layout, but the checkout, the blog or the category pages run on another template that never got it. Sessions look fine, conversions disappear.
A changed measurement ID: after a replatform, some pages carry the new G- and some the old one. The data splits across two properties in silence.
Consent gating: the tag loads only after cookies are accepted. Correct, until the CMP is replaced or the tag ends up in a category nobody opts into.
GTM without GA4: the container loads, but the GA4 tag inside it got paused or was never published. From the outside everything looks installed.
A deploy that drops it: a theme update, a caching layer, a rollback. The classic silent SEO change: nothing visibly breaks, the numbers just get worse.

Check every URL, not one URL

Pull the sitemap.xml, group the URLs by template (home, category, product, checkout, blog post, landing pages) and run the network check on at least one URL per template. Repeat after every release: a check that passes today says nothing about next Tuesday. By hand, across 20 client sites, that is not realistic, the problem behind our guide on monitoring client websites for changes.

How Deltio does it

Deltio scans every URL in your sitemap and records which marketing tags sit on each one: GA4, Google Tag Manager, Meta Pixel, Hotjar, Microsoft Clarity, LinkedIn Insight Tag and TikTok Pixel. It stores the tag IDs, compares each scan with the previous one and alerts on three events: a tag appeared, a tag disappeared, a tag ID changed. It also tracks the homepage cookie banner, so a swapped CMP does not go unnoticed, and the daily sitemap snapshot means new URLs get checked too. Alerts arrive by email and Slack, in your language, as covered in our piece on SEO change alerts.

Try it on one site

Add a client site, let the first scan run, and look at which URLs are missing GA4 today. Starter is £24 a month, or £20 a month billed annually, with a 14-day free trial.

Frequently asked questions

How do I check if GA4 is installed correctly?: View the page source and look for `gtag.js` and a measurement ID in the `G-XXXXXXXXXX` format. Then open DevTools, filter the Network tab for `collect` and reload the page: a correct install sends a request to `google-analytics.com/g/collect?v=2` with your measurement ID. Finally, confirm the event arrives in GA4 DebugView or the Realtime report.
How can I tell if GA4 is firing on every page?: You cannot tell from one page. The tag usually lives in a template, so it can be present on the homepage and missing on the checkout, the blog or a landing page built by a different team. Test at least one URL per template, and retest after every deploy.
Why does GA4 show no data even though the tag is on the page?: The most common causes are consent gating (the tag only loads after the cookie banner is accepted), a wrong or outdated measurement ID sending data to another property, a GTM container that loads without a published GA4 tag inside it, or a JavaScript error that stops the script before it runs.
Does Deltio alert me when the GA4 tag disappears?: Yes. Deltio checks the marketing tags on every URL in your sitemap and compares each scan with the previous one. If GA4 disappears from a page, appears somewhere new, or its measurement ID changes, you get an email and a Slack alert.
Which marketing tags can Deltio monitor?: GA4, Google Tag Manager, Meta Pixel, Hotjar, Microsoft Clarity, LinkedIn Insight Tag and TikTok Pixel. Deltio also detects the cookie banner or CMP on the homepage and tells you when the provider changes, which is a frequent cause of tags silently failing to load.
How much does Deltio cost?: Starter is £24 a month, or £20 a month if you pay annually. Professional is £49 a month and Enterprise is £119 a month. Every plan comes with a 14-day free trial.