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GTM Consent Mode Is Blocking the Sealmetrics Tag

The single most common cause of "Sealmetrics is missing data" is a Google Tag Manager container where the Sealmetrics tag is gated behind consent — either by GTM Consent Mode settings on the tag or by a consent management platform (Cookiebot, OneTrust, Usercentrics, Didomi, etc.) that blocks Custom HTML tags until the visitor clicks "Accept".

Sealmetrics is cookieless and consentless by design: it sets no cookies and uses no persistent identifiers, so it does not require consent to run. Gating it behind a consent banner does not add any compliance benefit — it only removes from your reports every visitor who ignores or declines the banner, which is routinely 30–70% of traffic.

Symptoms​

  • Traffic in Sealmetrics dropped sharply the day a CMP or Consent Mode went live.
  • Sealmetrics shows far fewer entrances than your server logs or ad platform clicks.
  • Data only appears for visits where the tester clicked "Accept all" on the banner.
  • In GTM Preview, the Sealmetrics tag shows as not fired or waiting for consent on page load.

Diagnosis​

  1. Open your site in a private window (no prior consent choice stored).
  2. Open Developer Tools → Network and filter by sealmetrics.
  3. Load a page and do not interact with the consent banner.
    • If no request to t.js appears until you click "Accept", the tag is consent-gated.
  4. Confirm in GTM Preview mode: select the pageview event and check the Sealmetrics tag's status. A tag held back by Consent Mode does not appear under Tags Fired on page load.
  5. Cross-check the dashboard: the Last hit timestamp on the Overview report updates within seconds of an unblocked hit. If it only moves after you grant consent, you have confirmed the cause.

Solution​

In GTM:

  1. Open the Sealmetrics tag (Custom HTML or template tag).
  2. Go to Advanced Settings → Consent Settings.
  3. Select No additional consent required.
  4. Make sure the tag's trigger is Initialization - All Pages (or All Pages) — not a custom "consent granted" event pushed by your CMP.
  5. If your CMP has its own "auto-blocking" feature that rewrites or blocks scripts by domain, add t.sealmetrics.com (or your first-party tracker domain) to its allowlist of non-consent-required vendors.
  6. Publish the container.

This is the configuration recommended in the Google Tag Manager integration guide: Sealmetrics is cookieless and consentless by design, so a CMP should not block it.

2. Use the canonical GTM pattern (stub + ?auto=0)​

If other tags in your container call sealmetrics(...) and the load order is not guaranteed, use the canonical pattern documented in Advanced GTM Integration: an inline buffer stub plus the tracker loaded with ?auto=0, and a separate tag that fires the pageview manually.

<script>
!function(w){w.sealmetrics=w.sealmetrics||function(){(w.sealmetrics.q=w.sealmetrics.q||[]).push(['pv',arguments])};w.sealmetrics.q=w.sealmetrics.q||[];w.sealmetrics.conv=w.sealmetrics.conv||function(){w.sealmetrics.q.push(['cv',arguments])};w.sealmetrics.micro=w.sealmetrics.micro||function(){w.sealmetrics.q.push(['mc',arguments])}}(window);
</script>
<script src="https://t.sealmetrics.com/t.js?id=YOUR_ACCOUNT_ID&auto=0" defer></script>

The stub queues any call made before the library loads and the library drains the queue in order, so no event is lost and no duplicate pageview is sent. On a single-page application where you also fire SPA pageviews manually from GTM, add &spa=0 to the script URL as well, so the tracker's automatic pageview on route changes does not double-count your manual one — see Duplicate pageviews.

What NOT to do​

  • Do not fire the Sealmetrics tag on your CMP's "consent granted" event. That trigger structurally excludes everyone who declines or ignores the banner, and it fires late — after the pageview context you wanted to measure.
  • Do not require analytics_storage consent for the tag. Sealmetrics does not use cookies or any storage, so that consent signal is irrelevant to it.
  • Do not delete the tag from GTM to "fix" a CMP conflict. Configure the exception instead — otherwise you keep the banner problem and lose all measurement.