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name: compatible-combinations description: "GA4 enforces strict rules about which dimensions and metrics can appear in the same request. Incompatible combinations return a 400 error: "The request's dimensions & metrics are incompatible.""

Compatible Dimension and Metric Combinations

GA4 enforces strict rules about which dimensions and metrics can appear in the same request. Incompatible combinations return a 400 error: "The request's dimensions & metrics are incompatible."

The core rule

GA4 data is scoped at three levels: event, session, and user. Mixing dimensions and metrics from incompatible scopes causes errors.

Scope	Example dimensions	Example metrics
Event	eventName, customEvent:*	eventCount
Session	sessionDefaultChannelGroup, sessionSource, sessionCampaignName	sessions, bounceRate, sessionKeyEventRate
User	firstUserDefaultChannelGroup, firstUserSource	totalUsers, newUsers

Most common incompatible pairs

Dimension	Incompatible metric	Use instead
sessionSource / sessionMedium / sessionCampaignName	eventCount	sessions
eventName	sessions	eventCount
promotionId / promotionName	most session/user metrics	only pair with promotionViews, promotionClicks
itemId / itemName	sessions, totalUsers	itemsViewed, addToCarts, ecommercePurchases
firstUserSource / firstUserMedium	sessions	totalUsers, newUsers

When you hit this error

The GA4 error message names the exact field to remove: "Please remove eventCount to make the request compatible for example."

Read the message literally — remove that field and replace it with a scope-compatible equivalent.

Safe combinations (always work)

• date + any metric
• deviceCategory + any metric
• country / city + any metric
• pagePath / pageTitle + screenPageViews, totalUsers, sessions
• sessionDefaultChannelGroup + sessions, totalUsers, bounceRate

Ecommerce-specific

Ecommerce metrics (ecommercePurchases, purchaseRevenue, addToCarts, itemsViewed) are event-scoped. Pair them with event-scoped or date/deviceCategory/geo dimensions — not with session campaign dimensions.