[Attribution Modeling (First-Click, Last-Click, Multi-Touch, Data-Driven)](atomicglue.co/glossary/attribution-modeling) — Attribution modeling is the framework that determines how credit for conversions is assigned to different marketing touchpoints along a customer's journey. Models range from simple (first-click gives all credit to the first touchpoint; last-click gives all credit to the final touchpoint) to sophisticated (multi-touch distributes credit across multiple touchpoints; data-driven uses machine learning to assign credit based on actual impact).
[Bounce Rate](atomicglue.co/glossary/bounce-rate) — Bounce rate is the percentage of sessions that were not engaged. In GA4, bounce rate is calculated as 100% minus engagement rate, making it a derived metric. This is a fundamentally different calculation from Universal Analytics where bounce rate measured single-page sessions with no interaction.
[CAC (Customer Acquisition Cost)](atomicglue.co/glossary/cac-customer-acquisition-cost) — Customer Acquisition Cost (CAC) is the total cost of acquiring a new customer, including all marketing and sales expenses divided by the number of new customers acquired in a given period. It is a core business metric that determines the efficiency and sustainability of growth.
[Conversion Rate](atomicglue.co/glossary/conversion-rate) — Conversion rate is the percentage of sessions or users who completed a desired action (a conversion) out of the total number of sessions or users. In GA4, it is calculated as key events per session or key events per user.
[Cookie Consent](atomicglue.co/glossary/cookie-consent) — Cookie consent is the legal requirement to obtain a user's permission before storing or accessing cookies and similar tracking technologies on their device. It is mandated by regulations like GDPR (EU), ePrivacy Directive (EU), CCPA/CPRA (California), and LGPD (Brazil), each with different requirements for how consent must be obtained and managed.
[Cookie Deprecation](atomicglue.co/glossary/cookie-deprecation) — Cookie deprecation refers to the phase-out of third-party cookies by web browsers, led by Google Chrome after Safari and Firefox already blocked them. This fundamentally changes how cross-site tracking, retargeting, and audience targeting work, forcing a shift to first-party data, privacy-preserving APIs, and alternative measurement methods.
[Customer Data Platform (CDP)](atomicglue.co/glossary/customer-data-platform) — A Customer Data Platform (CDP) is a system that unifies customer data from multiple sources into a single, persistent, and actionable customer profile. It enables personalized marketing across channels by creating a complete view of each customer that goes beyond what a CRM or marketing automation platform can provide alone.
[Data Layer](atomicglue.co/glossary/data-layer) — The data layer is a JavaScript object (typically named window.dataLayer) that stores structured information about a user's interaction with a website and passes it to Google Tag Manager. It acts as a bridge between your website's code and your tracking tags, ensuring clean, reliable data flows regardless of how tags are configured.
[Engagement Rate](atomicglue.co/glossary/engagement-rate) — Engagement rate is the percentage of sessions that qualify as 'engaged' in GA4. An engaged session is one where the user spent at least 10 seconds on the site, viewed 2 or more pages, or triggered a key event. Engagement rate is the inverse of bounce rate.
[Event Tracking](atomicglue.co/glossary/event-tracking) — Event tracking is the practice of recording specific user interactions on a website or app (clicks, form submissions, video views, purchases) as structured data points sent to an analytics platform. In GA4, event tracking is the fundamental data model: every measurable interaction is an event.
[First-Party Data](atomicglue.co/glossary/first-party-data) — First-party data is information a business collects directly from its own audience or customers through its own channels: website analytics, CRM data, purchase history, app usage, email engagement, and customer surveys. It is data you own and control, with direct consent from your users.
[Google Analytics 4 (GA4)](atomicglue.co/glossary/google-analytics-4-ga4) — Google Analytics 4 (GA4) is Google's event-based analytics platform that superseded Universal Analytics in July 2023. Unlike its predecessor which relied on session-and-pageview-centric tracking, GA4 uses an event-driven data model that unifies web and app data into a single property.
[Google Tag Manager](atomicglue.co/glossary/google-tag-manager) — Google Tag Manager (GTM) is a free tag management system that lets you deploy and manage marketing and analytics tags (tracking code snippets) on your website without modifying the underlying site code. It acts as a central hub that receives data from your site and routes it to platforms like Google Analytics, Google Ads, Meta Pixel, and hundreds of other tools.
[Heatmap](atomicglue.co/glossary/heatmap) — A heatmap is a visual representation of user interaction data on a webpage, using color coding to show where users click (click maps), move their mouse (move maps), or scroll (scroll maps). Heatmaps reveal which page elements get attention and which go unnoticed.
[Incrementality Testing](atomicglue.co/glossary/incrementality-testing) — Incrementality testing measures the causal impact of a marketing campaign by comparing outcomes between a group exposed to the campaign and a randomly selected holdout group that was not exposed. It answers the question: did this campaign actually drive additional conversions that would not have happened anyway?
[KPI](atomicglue.co/glossary/kpi) — A Key Performance Indicator (KPI) is a measurable value that tracks progress toward a specific business objective. In analytics, KPIs are the metrics that matter most: the few numbers that tell you whether your business is healthy and moving in the right direction. Not every metric is a KPI.
[Looker Studio](atomicglue.co/glossary/looker-studio) — Looker Studio (formerly Google Data Studio) is a free business intelligence and data visualization platform from Google. It connects to hundreds of data sources (GA4, Google Ads, BigQuery, Google Sheets, SQL databases, and more) to build interactive dashboards and reports.
[LTV (Lifetime Value)](atomicglue.co/glossary/ltv-lifetime-value) — Lifetime Value (LTV or CLV) is the predicted total revenue a business will earn from a single customer over the entire duration of their relationship. It is a forward-looking metric used to determine how much to spend on acquiring customers and which customer segments are most valuable.
[Marketing Mix Modeling (MMM)](atomicglue.co/glossary/marketing-mix-modeling-mmm) — Marketing Mix Modeling (MMM) is a statistical analysis technique that uses aggregate historical data (sales, media spend, pricing, economic factors) to estimate the sales impact and ROI of various marketing activities. Unlike attribution modeling which operates on user-level clickstream data, MMM works at the market level using regression-based models.
[Martech Stack](atomicglue.co/glossary/martech-stack) — A martech stack is the collection of marketing technology tools and platforms a company uses to execute, measure, and optimize its marketing programs. It typically includes a CRM, marketing automation platform, analytics tools, content management system, advertising platforms, and data infrastructure.
[Pageview](atomicglue.co/glossary/pageview) — A pageview is an event recorded when a user loads or reloads a webpage. In GA4, pageviews are tracked as the page_view event (part of automatically collected events) and each page_view contributes to a session.
[ROAS](atomicglue.co/glossary/roas) — Return on Ad Spend (ROAS) measures the gross revenue generated for every dollar spent on advertising. It is calculated as: Revenue from Ad Campaign / Cost of Ad Campaign. ROAS is the primary efficiency metric for paid advertising campaigns.
[Server-Side Tracking](atomicglue.co/glossary/server-side-tracking) — Server-side tracking moves the execution of tracking tags from the user's browser to a server you control. Instead of the browser sending data directly to dozens of third-party analytics and marketing endpoints, it sends one request to your server, which then processes, enriches, and forwards the data to the intended destinations.
[Session](atomicglue.co/glossary/session) — A session is a period of user activity on a website or app, bounded by a timeout. In GA4, a session starts when a user first arrives and ends after 30 minutes of inactivity (configurable) or at midnight. GA4 sessions are derived from the session_start event, not tracked as a separate hit type.
[Session Replay](atomicglue.co/glossary/session-replay) — Session replay is a technology that records a user's browsing session as a video-like playback, capturing mouse movements, clicks, scrolls, form interactions, and page navigation. It lets you watch exactly what users did on your site, revealing friction points, confusion, and opportunities that aggregate metrics cannot show.
[Traffic Source (Organic/Direct/Referral/Paid/Social)](atomicglue.co/glossary/traffic-source) — A traffic source is the origin of a visit to your website, categorized by how the user arrived. The primary categories are Organic (search engine), Direct (typed URL or bookmark), Referral (link from another site), Paid (ad click), and Social (link from a social platform). Understanding your traffic source mix is the foundation of acquisition analysis.
[UTM Parameters](atomicglue.co/glossary/utm-parameters) — UTM parameters are tags added to the end of a URL that tell your analytics platform where a visitor came from and which campaign brought them. The five standard UTM parameters are utm_source, utm_medium, utm_campaign, utm_content, and utm_term.
[Zero-Party Data](atomicglue.co/glossary/zero-party-data) — Zero-party data is data that a customer intentionally and proactively shares with a brand. It includes preferences, purchase intentions, personal context, and feedback. Unlike first-party data which is observed behavior, zero-party data is explicitly volunteered by the user.