> This page is part of the [Customer.io documentation](https://docs.customer.io). For the complete index, see [llms.txt](https://docs.customer.io/llms.txt).
> Last updated: September 1, 2026
> To take actions in Customer.io from an agent, use the [Customer.io CLI](https://docs.customer.io/ai/cli/get-started.md) or the [MCP server](https://docs.customer.io/ai/mcp/get-started.md).

# In-app messages

## How it works

An in-app message is a message that people see in your app. People won’t see your in-app messages until they open your app. If you set an *expiry* period for your message, and that time elapses before someone opens your app, they won’t see your message.

You can also set *page rules* to display your in-app messages when people visit specific pages in your app. However, to take advantage of page rules, you need to use [screen tracking](/integrations/sdk/flutter/tracking/screen-events/#auto-screenview) features. Screen tracking tells us the titles of your screens and which screen a person is on, so we can display in-app messages on the correct pages/screens in your app.

## Set up in-app messaging

In-app messages are disabled by default. Just pass the `inAppConfig` parameter in your `CustomerIOConfig` and add your [Site ID](https://fly.customer.io/env/last/settings/api_credentials).

```
import 'package:customer_io/customer_io.dart';
import 'package:customer_io/customer_io_config.dart';
import 'package:customer_io/customer_io_enums.dart';

CustomerIO.initialize(
  config: CustomerIOConfig(
    cdpApiKey: 'cdpApiKey',
    region: Region.us,
    inAppConfig: InAppConfig(siteId: 'siteId')
  ),
);
```

## Page rules

When you send an in-app message, you can set *Page Rules* determining the page(s) where your audience can see your message. Before you can take advantage of page rules, you need to:

1.  Track screens in your app. See [Screen Events](/integrations/sdk/flutter/tracking/screen-events/) for help sending `screen` events.
2.  Provide screen titles to whoever sets up in-app messages in Customer.io. If we don’t recognize the page that you set for a page rule, your audience will never see your message!

 ![Set up page rules to limit in app messages by page](https://docs.customer.io/images/in-app-page-rule.png)

Keep in mind: page rules are case sensitive. If you’re targeting your mobile app, make sure your page rules match the casing of the `title` in your `screen` events. If you’re targeting your website, your page rules should always be lowercase.

 ![The first page rule is Web contains /dashboard. The second page rule is iOS contains Dashboard.](https://docs.customer.io/images/page-rule-case-sensitive.png)

[GitHub project](https://github.com/customerio/customerio-flutter "View the Flutter SDK on GitHub")

Version

4.4.0 (Current)2.x (2.9.0)1.x (1.5.2)

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