/compatible-combinations

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.