Google Analytics 4 (GA4) continues to evolve, and one of the most anticipated additions has finally arrived: Annotations.

Long appreciated in Universal Analytics, annotations help marketers and analysts provide crucial context directly within the analytics platform. In this article, we’ll cover what annotations are, where to find them in GA4, when and why to use them, how to create them, and best practices for marketing teams.

What are Annotations in GA4?

Annotations in Google Analytics 4 are a simple yet powerful way to add context to your data. Think of them as digital sticky notes you can attach to your reports, marking important moments like campaign launches, website updates, system outages, or changes to your tracking setup.

If you've ever looked at a sudden spike or drop in traffic and thought, “Wait… what happened that day?” - annotations are the answer. Instead of relying on memory, Slack threads, or scattered spreadsheets, you can add a clear, time-stamped note right inside GA4 to explain what changed and why it matters. For teams managing multiple campaigns, websites, or stakeholders, annotations help everyone stay aligned and informed. They reduce guesswork, provide historical insight, and keep your reporting rooted in real-world events. In short, annotations are like a timeline of your marketing and analytics story - written in your own words, exactly where you need it most.

Where do Annotations Appear in GA4?

Google officially rolled out annotations to GA4 in March 2025, answering one of the most frequent requests from marketers and analysts since the sunsetting of Universal Analytics. This long-awaited feature brings much-needed context back into the native reporting experience. So, where exactly can you find annotations in GA4, and how do they show up? Here’s what you need to know:

• Annotations live within the “Reports” section of GA4, specifically on the timeline (line) charts found in standard reports like “Traffic acquisition” or “Events.”
• They’re visually marked, usually with a small icon or indicator on the chart. To view the details of an annotation, hover over a specific date on the graph. If an annotation exists for that day, a tooltip will display the note.
• Access and visibility depend on user roles -
• Users with Editor or Administrator permissions can create, edit, and delete annotations.
• Users with Viewer access can see annotations but not modify them.

It's worth noting that Google may still be gradually rolling out this feature across accounts. If you don’t see it yet, it’s likely on the way; keep an eye on your reports over the coming weeks. This feature helps bring your charts to life with real-world context. You can stop playing detective every time your data changes and start building a clearer narrative around your analytics.

When Should You Use Annotations?

Annotations are your best friend when it comes to keeping track of moments that might explain why your data suddenly changed. Any time something happens that could influence traffic, conversions, or user behaviour, big or small, it’s worth making a note of it directly in GA4.

Here are a few common situations where adding an annotation can save you (and your team) a lot of guesswork later:

• Launching a campaign - Maybe your Google Ads campaign went live on May 1st, or you dropped a big email blast at 9 a.m. last Tuesday. Marking that in GA4 helps connect the dots when you see a traffic spike (or a dip) shortly after.
• Making website changes - Whether you launched a new homepage, started an A/B test, or removed an underperforming product page, those updates can impact user behaviour. An annotation lets your future self, and your team know what changed and when.
• Updating your tracking - Did your dev team tweak your Google Tag Manager setup? Did you implement new event tracking or change how conversions are counted? These types of back-end updates can significantly alter your data. Make sure it’s documented.
• Reacting to external events - Maybe your brand was mentioned on a popular podcast, went viral on TikTok, or got a shoutout in a major newsletter. These unexpected boosts in traffic are a good problem to have, and even better when explained with a quick note.
• Dealing with outages or bugs - If your site went down for maintenance, your tags stopped firing, or GA4 stopped collecting data for a day. Those are moments you definitely want to annotate. Otherwise, someone might misinterpret a drop in data as a performance issue.

The key takeaway? Add annotations as close to real-time as possible. Trying to piece together what happened two weeks later is frustrating, especially when your memory or your calendar comes up short. A 10-second annotation today can save you hours of head-scratching tomorrow.

If you need support in the implementation of annotations or if you require analytics assistance, Arekibo is a specialist Google Analytics Agency. Get in touch today.