What are Google Analytics annotations?

Google Analytics annotations are notes you can attach to a specific date in your analytics reports to record what was happening at that moment. This could be a marketing campaign launch, a site redesign, a tracking change, a press mention, or any external event worth remembering when you look back at the data later.

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They appear as small markers on timeline graphs and are visible to anyone with access to the property, which makes them useful for giving context to traffic spikes or drops that would otherwise be confusing months later. Annotations were a native feature in Universal Analytics but were not carried over into Google Analytics 4, which has been a common complaint among practitioners since the GA4 migration. Workarounds in GA4 include using custom events, exploration report notes, or external documentation tools to preserve the same workflow.