[GA4] About traffic-source dimensions

In Google Analytics, traffic-source dimensions are the building blocks for understanding and analyzing attribution as well as session and user acquisition. They provide the raw data that's used to determine where your visitors are coming from and how they interact with your website or app.

The following are the most common traffic source dimensions:

Dimension	Description
Source	Identifies the specific platform, website, app, or online location that referred a user to your property, giving you precise attribution for the user's last click or interaction. Examples include "google" (search engine), "facebook.com" (referring site), "spring_newsletter" (email campaign), and "direct" (typed URL or bookmark).
Medium	Categorizes the type of traffic your property receives, such as through email marketing, organic search, paid advertising, referrals, or social media. Common mediums include "organic" (unpaid search), "cpc" (paid search), "referral," "social," "email," and "none" (direct traffic).
Campaign	Represents a marketing initiative with a specific objective used to measure its effectiveness.
Campaign ID	Identifies a specific campaign or promotion; use the same IDs for uploading cost data.
Source platform	Broadly classifies traffic sources, grouping them by the referring platform to provide a generalized view of traffic origins. Examples may include advertising platforms like “Google Ads”, marketing orchestration platforms like “SFMC” or platforms used to manage product listings like “Shopping Free Listings” (for product information managed via Google Merchant Center).
Default channel group	Automatically segments traffic into broad channels based on traffic source data, providing a simplified overview of traffic patterns.

Where advertising traffic source data comes from

With Analytics, you have the option to collect traffic-source data by manually tagging your destination URLs or by creating integrations between Analytics and your ad platforms and using the auto-tagging feature available with those integrations.

With both manual tagging and auto-tagging, the parameters and parameter values appear as dimensions and dimension values in your reports and explorations and in the audience and segment builders.

Auto-tagging

For supported advertising platforms like Google Ads, Search Ads 360, and Display & Video 360, you can connect your advertising accounts and enable auto-tagging. Auto-tagging adds additional information to your URLs, simplifying the data collection process.

When you set up auto-tagging, a Google Click Identifier (GCLID) or DoubleClick Identifier (DCLID) is added to your destination URLs. GCLID and DCLID are parameters added by the ad platform to your URLs so you can identify the campaign and other attributes of an ad click.

Manual tagging with UTM parameters

Manual tagging involves manually adding UTM parameters to the end of your final URLs. UTM parameters allow Google Analytics to identify the source, medium, campaign, and other traffic source information about your ads, providing valuable insights into their performance.

Use manual tagging in combination with auto-tagging in some specific cases

For advertisers, auto-tagging unlocks many benefits in Google Analytics. For example, you automatically gain access to new dimensions in your reports and you are able to create more granular audiences based on these additional dimensions. Using auto-tagging is also required to create conversions from your Google Analytics key events in Google Ads, Display & Video 360, Campaign Manager 360 or Search Ads 360.

However, even if auto-tagging is enabled, there are some cases where the Google Click Identifier (GCLID) or DoubleClick Identifier (DCLID) cannot be used as intended. This can happen, for example, when ad_user_data is denied through your Consent Mode implementation. In these situations, the automatic retrieval of dimensions from the advertising platform might not be possible. As a result, you might see (organic) labels for cross-channel traffic source dimensions in Google Analytics.

The following table shows how traffic-source dimensions are updated in these instances:

Integration	Landing Page has	Source/Medium	Campaign	Default channel group	Source Platform
Google Ads	Auto-tagging (GCLID)	google/cpc	(organic)	Paid Search	Manual
	Auto-tagging (GCLID) and manual tagging (UTMs)	google/cpc	[utm_campaign]	Paid Search	Manual
DV360	Auto-tagging (DCLID)	Empty (results in "Direct")	Empty (results in "Direct")	Empty (results in "Unassigned")	Manual
	Auto-tagging (DCLID) and manual tagging (UTMs)	[utm_source] / [utm_medium]	[utm_campaign]	based on UTM parameters	Manual
	Auto-tagging (GCLID)	google/cpc	(organic)	Paid Search	Manual
	Auto-tagging (GCLID) and manual tagging (UTMs)	google/cpc	[utm_campaign]	Paid Search	Manual
SA360	Auto-tagging (GCLID + gclsrc)	Google Ads: google/cpc Other Engines: Empty (results in "Direct")	Google Ads: (organic) Other Engines: Empty (results in "Direct")	Google Ads: Paid Search Other Engines: Empty (results in "Unassigned")	Manual
	Auto-tagging (GCLID + gclsrc) and manual tagging (UTMs)	Google Ads: google/cpc Other Engines: [utm_source / utm_medium]	[utm_campaign]	Google Ads: Paid Search Other Engines: based on UTM parameters	Manual