18. Glossary

One line per term; the link goes to the chapter that earns it. Terms in italics inside a definition have their own entry.

Ad blocker — browser extension or DNS filter that cancels requests to known tracking hostnames/paths via filter lists (EasyList/EasyPrivacy). Ch. 3

Advanced matching — Meta's name for sending hashed PII with pixel/CAPI events to improve identity matching. Ch. 13

action_source — required CAPI field declaring an event's channel (website, physical_store…). Ch. 13

Attribution — a platform's act of crediting a conversion to an ad interaction, via click IDs, cookies, or hashed PII, within an attribution window. Ch. 2

Beacon (sendBeacon) — browser API that queues a request to survive page navigation; GA4's transport of choice. Ch. 2

CAPI (Conversions API) — Meta's server-to-server events endpoint; the server leg of the redundant setup. Ch. 13

Click ID — per-click URL parameter (gclid, fbclid, ttclid, msclkid, li_fat_id) that lets a platform join a later conversion to the ad click. Ch. 2

Client (sGTM) — the inbound adapter in a server container: claims HTTP requests it recognizes, parses them into events, and owns the HTTP response. Ch. 10

Client ID — GA's per-browser identifier (_ga cookie / cid parameter; FPID server-side). Ch. 2

CMP (Consent Management Platform) — banner + consent storage + the broadcast of consent state to tags. Ch. 17

CNAME cloaking — pointing a first-party subdomain at vendor infrastructure via CNAME; Safari detects it and caps the subdomain's cookies at 7 days. Ch. 11

Consent Mode (v2) — Google's machine-readable consent signals (ad_storage, analytics_storage, ad_user_data, ad_personalization); v2 added the last two, EEA-mandatory since 2024. Ch. 17

Container — one tag configuration for one site/app; compiled to gtm.js (web) or run by a tagging server (server). Ch. 4

Conversion — an event plus a successful platform-side identity match; each platform defines it slightly differently (GA4 key event, Ads click-join, Meta matched standard event). Ch. 2

Conversion Linker — the GTM tag that captures click IDs into first-party _gcl_* cookies; mandatory for Google Ads attribution. Ch. 7

Cookie, first-party / third-party — keyed to whether the cookie's domain matches the site in the address bar; third-party cookies are blocked in Safari/Firefox and restricted in Chrome. Ch. 2

Custom Event trigger — trigger matching the event key of data layer pushes; the workhorse of serious containers. Ch. 6

Custom loader — serving the container script and endpoints under randomized first-party paths to evade path-based filter rules. Ch. 11

Data layer — the array+model pair (dataLayer) through which the page states facts and GTM consumes them; the contract between app and container. Ch. 5

Data Layer Variable (DLV) — variable reading a dot-path from the data layer's internal model (use Version 2). Ch. 6

DebugView — GA4's live per-device event stream; the platform-layer verification tool. Ch. 8

Deduplication — collapsing the same event sent from two legs (pixel + server) into one, keyed on event_id (+ event name). Ch. 13

EMQ (Event Match Quality) — Meta's 1–10 per-event score of identity match-key quality; the KPI of a CAPI setup. Ch. 13

Enhanced conversions — Google's hashed-PII augmentation of Ads conversions, recovering joins when click-ID chains break. Ch. 14

ePrivacy — the EU rule requiring prior consent for storing/reading anything non-essential on the device — the "cookie law". Ch. 17

Event data model — the common schema a client parses requests into and tags consume — sGTM's lingua franca. Ch. 10

event_id — the shared per-event-instance ID minted in the data layer and carried by both browser and server legs for deduplication. Ch. 13

eventCallback / eventTimeout — data layer push companions for the "push, then navigate" race. Ch. 5

_fbp / _fbc / fbclid — Meta's browser-ID cookie, captured-click cookie, and the click ID that feeds it. Ch. 2

FPID — the server-managed, HttpOnly, HTTP-set first-party client-ID cookie sGTM's GA4 client can own; durable where JS cookies are capped. Ch. 11

gclid / _gcl_au — Google Ads' click ID and the conversion-linker cookie family that stores it. Ch. 2

GDPR — the EU regulation governing personal-data processing; consent is the working legal basis for tracking. Ch. 17

gtag.js / the Google tag — Google's per-product loader and the underlying machinery GA4/Ads tags share; coexists with (and is superseded by) GTM. Ch. 4

gtm.js — your web container compiled to JavaScript, served from Google's CDN (or first-party via sGTM). Ch. 4

ITP / ETP — Safari's Intelligent Tracking Prevention and Firefox's Enhanced Tracking Protection; sources of the 7-day/24-hour JS-cookie caps. Ch. 3

Key event — GA4's name for an event flagged as a conversion (in GA4 Admin, not GTM). Ch. 7

Lookup Table — declarative input→output variable mapping; the standard tool for environment-dependent IDs. Ch. 6

Measurement Protocol (public API) — Google's keyed (api_secret) API for sending GA4 events from code; distinct from the native collect dialect the server GA4 tag speaks. Ch. 12

Pixel — historically a 1×1 tracking image; today shorthand for a vendor's browser tag. Ch. 1

Preview mode / preview server — GTM's debug machinery: a draft build in your browser (web) or a dedicated debug instance streaming claimed requests and outbound calls (server). Ch. 8 / Ch. 10

Redundant setup — running browser pixel and server API together, deduplicated, so each leg catches what the other drops. Ch. 13

Server container / sGTM — the GTM container type that runs as a Node app on infrastructure you choose; clients in, tags out. Ch. 10

Tag — code that sends data to a platform: a template-generated vendor call (web) or an outbound server-to-server API call (server). Ch. 1 / Ch. 10

Tag sequencing — setup/cleanup tags ordering execution within one event (base pixel before event pixel). Ch. 6

Tagging server — the stateless production instance(s) of the server container, as opposed to the preview server. Ch. 10

TMS (Tag Management System) — one snippet + a console managing all tags; GTM's category. Ch. 1

Transformation — sGTM feature that edits/augments/redacts events before tags consume them; the central enforcement point. Ch. 10

transport_url — the GA4 web-tag setting that re-points the browser's event stream at your first-party tagging server. Ch. 11

Trigger — a stateless per-message condition deciding when tags fire. Ch. 6

Trigger group — fires once after all member triggers have fired on a page. Ch. 6

UTM parameters — utm_* URL tags feeding GA4 attribution ("Urchin Tracking Module" — the 2005 acquisition lives on). Ch. 1 / Ch. 7

Variable — a named lazy lookup resolved at fire time, per event. Ch. 6

Version / Workspace — immutable published snapshot / editable draft branch of a container. Ch. 4

Zombie tag — a forgotten tag from a dead campaign, still firing, still leaking; the tag-soup era's ghost. Ch. 1

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That's the series. If you read it in order: you now know why tag managers exist, how the browser half really works, why it broke, and how the server half fixes what can be fixed — including what every vendor in this market, us included, is actually selling. Put it to work: open a container you own, run the Chapter 8 five-question workflow on a real event, and trace it all the way to a platform. The docs for our own stack live at Pixel Logic Server.