container audit
GTM-M4HGZ8T
This container ships 58 hand-written scripts (29 KB of JavaScript) to every visitor — more than 95% of the 46,522 containers we have measured. That is an application's worth of code, delivered as tag configuration.
Tags147
Custom scripts58
Third parties19
Delivered572 KB
Versions156
What we observed
A real browser loaded wowow.co.jp a month ago and recorded every request it made. This is what happened, as distinct from what the container is configured to do. It is one page load — anything that fires only deeper in the site did not fire here.
Container loaded from
googletagmanager.com — GoogleMeasurement sent to
google-analytics.com — GoogleConsent
no consent gate responded on this page, so there was nothing to hold measurement back (banners are often shown only to visitors in certain regions, and this was not a European visit).
Third parties contacted
25 hosts — dev.visualwebsiteoptimizer.com, www.googletagmanager.com, cdnjs.cloudflare.com, analytics.google.com, www.google.co.il, stats.g.doubleclick.net, fonts.googleapis.com, dmp.im-apps.net, and 17 more
dataLayer events seen
gtm.js, gtm.dom, im-ready, gtm.load, gtm.scrollDepth
Where the data goes
Not observed — on the page we loaded, measurement went to Google and nowhere else. observed on wowow.co.jp More info »
Findings
Ordered by consequence. review has a concrete cost when it bites; info is real but depends on your setup. Seen is how common it is across the containers we have measured — reported separately on purpose, because common and harmless are different claims.
reviewdocument.write (26)
26 pieces of custom code call document.write.
Whydocument.write blocks the HTML parser while it runs, and browsers ignore it entirely once the page has finished parsing — so an async-loaded tag using it can silently do nothing.
CheckIf these tags fire on page load they are costing render time; if they fire later they may not be working at all. Worth confirming the tag still does what it was added to do.
Seenseen in 18.4% of 46,522 containers measured
reviewHardcoded http:// URL (3)
3 pieces of custom code reference a plain http:// address.
WhyOn an https:// page the browser blocks or upgrades these. Blocked means the tag quietly stops working; upgraded only works if that host also serves https.
CheckCheck whether the hosts below still respond over https, and update the URLs.
Seenseen in 12.8% of 46,522 containers measured
reviewWrites cookies directly (2)
2 pieces of custom code set cookies in code.
WhyCookies set this way bypass GTM's consent settings, because the consent checks live in the tag templates rather than in raw JavaScript.
CheckIf any of these cookies are used for analytics or advertising, confirm they are still gated on a consent decision.
Seenseen in 21.2% of 46,522 containers measured
infoLoads JavaScript from another host (9)
9 pieces of custom code fetch and run JavaScript from another host.
WhyWhatever that host serves executes with full access to the page — it can read the DOM, cookies and form fields. The code is not in this container, so it can change at any time without any change here.
CheckConfirm you recognise every host below and that someone owns the relationship. A host you cannot name is the one to chase.
Seenseen in 54.4% of 46,522 containers measured
infoUses browser storage (5)
5 pieces of custom code read or write localStorage or sessionStorage.
WhyBrowser storage persists across visits and is not covered by cookie consent tooling, so it is easy to overlook when auditing what you keep on a visitor's device.
CheckConfirm nothing personal is being kept there, and that it is covered by your privacy notice.
Seenseen in 23.3% of 46,522 containers measured
infoConsent configuration detected (1)
The container declares one or more consent signals.
WhyConsent handling is present in the container. This describes what the artifact declares; what actually happened on the page is measured separately, above.
CheckConfirm these settings match the consent policy you intend to enforce, and compare them with the before-and-after observation.
Seenseen in 44.6% of 46,522 containers measured
Third parties it can reach
Each host is a party that can execute code or receive data in a visitor's browser. Follow one to see who else loads it. More info »
bypass.ad-stir.com ×8www.googleadservices.com ×6i.smartnews-ads.com ×4ad.doubleclick.net ×3atb.im-apps.net ×3bs.ad-stir.com ×3d.line-cdn.net ×3d.line-scdn.net ×3dev.visualwebsiteoptimizer.com ×3googleads.g.doubleclick.net ×3tr.line.me ×3www.google-analytics.com ×3b6.im-apps.net ×2cd.ladsp.com ×2mtm.im-apps.net ×2assets.gunosy.com ×1cdn.hera.d2c.ne.jp ×1dmp.im-apps.net ×1score.im-apps.net ×1
What the custom templates can do
Custom templates are third-party code shipped inside the container. Injecting scripts and running page globals is ordinary for them — most tag templates need it to work — so this is an inventory, not a warning. It lists the capability each template declares so you can match it against templates you meant to install.
__cvt_KF8K9 gallery injects code from analytics.tiktok.com · runs page-level globals__cvt_5R7R4 gallery injects code from tag.flvcdn.net · runs page-level globals__cvt_91026002_12 private injects code from s.yimg.jp · runs page-level globals__cvt_91026002_17 private injects code from connect.facebook.net · runs page-level globals__cvt_91026002_260 private injects code from static.ads-twitter.com · runs page-level globals__cvt_91026002_262 private injects code from static.ads-twitter.com · runs page-level globals__cvt_91026002_301 private injects code from p.teads.tv · runs page-level globals__cvt_91026002_338 private injects code from www.clarity.ms · runs page-level globals__cvt_91026002_35 private injects code from s.yimg.jp · runs page-level globals__cvt_91026002_453 private injects code from s.yimg.jp · runs page-level globals__cvt_PLV57 gallery injects code from tag.flvcdn.net · runs page-level globalsDetected on
Sites observed loading this container. A container used across many hosts is a shared template; one on a single host is a bespoke build. Follow a site to see every container it loads.
What this audit describes
Containers change. These findings describe one specific artifact, and you can re-fetch it to check this reading.
| Container | GTM-M4HGZ8T |
|---|---|
| Published version | 156 — the identity of this configuration. It changes only when someone publishes. |
| Read at | 2026-08-22 10:23:13 UTC (a month ago) |
| Source | https://www.googletagmanager.com/gtm.js?id=GTM-M4HGZ8T |
| Body checksum | ef1b45faa046a4462b6b48c934fb25629ad0273bd902c3163c22729933f32a68Evidence of the exact bytes we read, not an identity: Google varies the response per request, so re-fetching an unchanged container yields a different checksum. Compare the published version instead. |
Re-audit
This reading is from a month ago. A container can be republished at any time, and nothing here updates on its own — a fresh read is the only way to know whether it still says this. Running it again replaces this page in place, so the link keeps working.
Put this container under version control. Tagora exports it to a repository you own, so every change arrives as a pull request. How it works »