GA4 Annotations: How to Mark Changes in Your Reports

If you have ever looked at a traffic drop in GA4 and had no idea what caused it, GA4 annotations are the fix. They let you pin a short note to a date on your report charts, such as “New site launched” or “Spring sale started”, so anyone looking at the data later knows what changed and when.

Google added annotations to Google Analytics 4 on 20 March 2025. In this guide I explain how they work, how to add one, who can create them, and the simple system I use to keep them useful.

What Are GA4 Annotations?

An annotation is a small note tied to a single date or a date range in your GA4 property. It shows up as a marker under the line charts in your reports. Hover over the marker and you see the note.

Google’s own description is that annotations help you record events, explain changes in data and highlight key observations. In plain words, they answer the question every report eventually raises: “Why did this line move?”

Each annotation has four parts:

• Title: up to 60 characters. This is what people see first.
• Description: up to 150 characters for extra context.
• Date: one day, or a start and end date for something that runs longer.
• Colour: a colour you pick, which helps you group notes by type.

Annotations belong to the property, not to your personal account. Everyone with access to that property sees the same notes.

Why GA4 Annotations Matter for SEO and Marketing

Universal Analytics had annotations for years. When it was switched off, many of us lost that habit, and GA4 had no built-in way to record changes. People kept notes in spreadsheets, Slack threads or their own heads.

The trouble is that memory fades fast. Six months after a redesign, nobody remembers the exact week the new menu went live. When traffic dips, you end up guessing.

Annotations fix that because the note sits right on the chart, next to the data it explains. Here is where I find them most useful:

• Google updates. When a core update rolls out, I note the start date so I can compare traffic before and after. If you are checking the impact of the latest one, my guide on what to check after the March 2025 core update pairs well with an annotation on the rollout dates.
• Site changes. Migrations, redesigns, new templates, URL changes and big content updates.
• Tracking changes. New tags, consent banner changes, or a broken tag that stopped data for a few days.
• Campaigns. Email sends, paid campaigns, sales and press coverage.
• Outside events. Holidays, seasonal peaks, a site outage or a competitor’s big launch.

In my experience, the biggest benefit is for teams. A new person, an agency or a manager can open a report and understand the story without asking anyone.

Where Annotations Show Up in GA4

At launch, Google said annotations appear on line graphs in the overview reports, the detailed reports and the Advertising section. Once you create one, it shows across every report and report card that has a line chart, not just the report you were in.

Under the line chart you will see a small icon on the annotated date. You can:

• Hover over the icon to see a quick card with the title and description.
• Click the icon to open a side panel that lists the annotations for that period.

There are some places annotations do not appear, and this catches people out:

• Explorations. Annotations do not show in Explore reports such as free-form or funnel explorations.
• Bar charts and tables. They only appear on line charts.
• Looker Studio. Dashboards built on GA4 data do not pull in annotations.

If most of your reporting happens in Looker Studio, keep that in mind. I still add annotations in GA4, because that is where I go when I need to investigate a change.

System Annotations From Google

Google can also add its own annotations. These are system annotations, created when something happens that affects your data, such as a data collection issue on a certain date.

System annotations look like normal ones, but you cannot edit or delete them. Hover over the icon to read what Google flagged. If you see one, take it seriously and check your tracking for that date.

Who Can Create and Edit Annotations

Permissions are set at the property level. At the time of writing, this is how it works:

• Editor and Administrator: can create, edit and delete annotations.
• Analyst, Marketer and Viewer: can see annotations on reports but cannot add or change them.

This means a person with view-only access cannot leave a note, even if they spotted the reason for a spike. If you want someone to add annotations, they need Editor access to that property. Before you give that, remember Editor also lets them change settings such as events and data streams.

If you are not sure which role someone has, my guide on how to give access to Google Analytics 4 explains each role and how to change it.

My habit is to keep Editor access small. I would rather have one or two people own annotations and let others send them notes to add.

How to Add an Annotation in GA4

Adding an annotation takes less than a minute. Here are the steps:

1. Open your GA4 property and click Reports in the left menu.
2. Open any report with a line chart, such as Reports snapshot or Traffic acquisition.
3. Set the date range so it includes the date you want to note.
4. Right-click the data point on the line chart for that date, then click Add annotation.
5. Type a clear title (60 characters or fewer) and, if needed, a short description (150 characters or fewer).
6. Choose a single date or a date range, and pick a colour.
7. Click Create annotation. The marker now appears under line charts across your reports.

You can add annotations for past dates as well, so you can go back and fill in history. I recommend doing this once when you start, which I cover below.

For developers, Google also lets you create annotations through the Google Analytics Admin API. That is handy if you want to add notes automatically, for example every time you deploy a new release. Most small businesses will not need this.

How to Edit or Delete an Annotation

To change a note, click the annotation icon under the chart to open it, then edit the title, description, dates or colour. You can delete it from the same place.

Only Editors and Administrators can do this, and only for annotations that people created. System annotations from Google stay as they are.

Hiding Annotations

If the markers get in the way, the annotations panel has a setting to hide or show them. This hides all annotations at once, including date range bars. It does not delete anything, so you can switch them back on later.

Single Date vs Date Range: Which to Use

A single-date annotation marks one day. A date range annotation covers a period and shows as a bar across those dates.

I use single dates for things that happen at a point in time:

• A site migration or redesign going live
• A tracking tag being added or fixed
• An email or social post going out

I use date ranges for things that run over time:

• A Google core update rollout
• A sale or paid campaign
• A period where tracking was broken

One warning: lots of overlapping ranges make charts hard to read. Google itself suggests using single-date annotations if you expect many with overlapping dates. When a campaign runs for months, I often add one note for the start and one for the end instead of a long bar.

What to Annotate: A Simple System

The value of annotations depends on being consistent. If only some changes get noted, people stop trusting them. Here is the colour system I suggest. GA4 does not assign meanings to colours, so agree on your own and write them down.

The exact colours do not matter much. What matters is that everyone uses the same ones.

Write Titles People Can Scan

Titles show first, so make them do the work. I like a short prefix followed by what happened. For example:

• SEO: March 2025 core update starts
• Site: New product page template live
• Tracking: Purchase event fixed
• Campaign: Spring sale email sent

Use the description for the detail that helps later: which pages were affected, who made the change, or a ticket number. Keep it short, because you only have 150 characters.

Annotations Work by Day, Not by Hour

You can only pick days, not times. If timing within the day matters, such as a tag going live in the afternoon, add the time to the title or description. Otherwise someone may later wonder why only half the day looks different.

Common Mistakes With GA4 Annotations

These are the problems I usually see when teams start using annotations:

• Annotating everything. A note for every blog post makes the chart cluttered. Save annotations for changes that could move your numbers.
• Vague titles. “Changes made” or “Update” helps nobody six months later. Say what changed.
• Wrong property. Annotations belong to one property. If you have several properties, such as separate sites or a test property, add the note to the right one, and to each one it affects.
• Only one person adds notes. If the SEO lead is the only one annotating, the paid team’s campaigns go missing. Agree on who adds what.
• Treating a note as proof. An annotation shows that two things happened at the same time. It does not prove one caused the other. Always check the data in more detail.

How to Backfill Past Changes

When annotations are new to you, your property has months or years of data with no notes. I recommend spending half an hour filling in the big events. This makes year-on-year comparisons much easier.

Here is how I approach it:

1. Check your change logs, project tools or email for big site launches and migrations.
2. Look at your campaign calendar for major sales and launches.
3. Add the dates of the Google core updates that affected your site, using the dates on Google’s Search Status Dashboard.
4. Look for odd spikes or gaps in your charts and add notes where you know the reason.

Do not worry about getting every small detail. The big events give you most of the value.

If your tracking was set up in a hurry, this is also a good time to check it. My GA4 setup guide covers the basics I check on every property, and a tracking fix is exactly the kind of change worth annotating.

Annotations and Your Other Tools

GA4 annotations only live in GA4. They do not appear in Search Console, Google Ads or Looker Studio. If you report from several tools, you may still want one shared change log, such as a simple spreadsheet, as your master record.

In my setup, the spreadsheet is the full record and GA4 annotations are the short version people see on the chart. That way nothing is lost if someone forgets to add a note in one place.

If you use Google Tag Manager, it is worth adding an annotation whenever you publish a container version that changes what GA4 tracks. My guide on Google Tag Manager for SEO covers the tags most sites use.

Conclusion: Start Using GA4 Annotations Today

GA4 annotations are a small feature that saves a lot of guessing. They let you mark site changes, campaigns, tracking fixes and Google updates right on your report charts, so the reason behind a spike or drop is never lost.

My advice is simple. Make sure the right people have Editor access, agree on a colour and title system, and spend a short session adding your biggest past changes. Then add a note every time something important changes. Google’s help page on annotations has the official details if you want to check the limits.

A good next step is to annotate the March 2025 core update dates in your property, then compare your organic traffic before and after.