How to Create a Blur Effect in a Flutter App to Protect Sensitive Data in the Background

Creating a blur effect in a Flutter app can be an effective solution to protect sensitive information when the app is in the background. You may have seen this feature in mobile banking apps, where the screen appears blurred when viewed in the recent apps view.

This effect is not just a visually appealing element—it also serves as an extra security layer to prevent important data from being seen by others. In this article, you will learn how to implement a similar feature in your Flutter app to enhance user privacy and security.

Why Add a Blur Effect in Flutter?

When a user switches apps, the OS takes a snapshot of your app’s last visible state for use in the app switcher. If your app shows:

• Account balances
• Medical data
• Chat messages
• Personal content

…it could all be visible in that preview. 🫣

By adding a blur effect in a Flutter app when the application is inactive, you can enhance privacy while also providing a sense of security for users. This technique is a practical solution to prevent sensitive information from being easily seen when the app is in the background.

What We’ll Build

We’ll use a combination of:

• WidgetsBindingObserver to detect app lifecycle changes
• A full-screen blur overlay
• Stack widget to toggle the overlay dynamically

Result:

✅ When app goes into the background → screen is blurred
✅ When app returns to foreground → screen is clear again

How to Create a Blur Effect in a Flutter App

1. Create a Blur Overlay Widget

import 'dart:ui';

import 'package:flutter/material.dart';

class BlurOverlay extends StatelessWidget {
  const BlurOverlay({super.key});

  @override
  Widget build(BuildContext context) {
    return Positioned.fill(
      child: BackdropFilter(
        filter: ImageFilter.blur(sigmaX: 15, sigmaY: 15),
        child: ColoredBox(color: Colors.black.withValues(alpha: 0.5)),
      ),
    );
  }
}

2. Create a Lifecycle Wrapper

import 'package:counter_application/blur_in_background/blur_overlay.dart';
import 'package:flutter/material.dart';

class BlurInBackgroundWrapper extends StatefulWidget {
  final Widget child;

  const BlurInBackgroundWrapper({super.key, required this.child});

  @override
  State<BlurInBackgroundWrapper> createState() =>
      _BlurInBackgroundWrapperState();
}

class _BlurInBackgroundWrapperState extends State<BlurInBackgroundWrapper>
    with WidgetsBindingObserver {
  bool _isBlurred = false;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    setState(() {
      _isBlurred =
          state == AppLifecycleState.inactive ||
          state == AppLifecycleState.paused;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Stack(children: [widget.child, if (_isBlurred) const BlurOverlay()]);
  }
}

3. Wrap Your App With the Privacy Overlay

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
      ),
      builder: (context, child) => BlurInBackgroundWrapper(child: child!),
      home: MySensitiveInfoScreen(),  //first screen
    );
  }
}

4. Example of first screen

import 'package:flutter/material.dart';

class MySensitiveInfoScreen extends StatelessWidget {
  const MySensitiveInfoScreen({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Hide your sensitive info'),
        backgroundColor: Colors.indigoAccent,
      ),
      body: const Center(
        child: Padding(
          padding: EdgeInsets.all(16),
          child: Column(
            spacing: 20,
            children: [
              Text(
                'Smart Privacy Guard',
                style: TextStyle(fontSize: 24, fontWeight: FontWeight.bold),
              ),
              Text(
                'Sensitive information is automatically obscured when the app loses focus',
                style: TextStyle(fontSize: 20),
              ),
              Text(
                'Blurring your whole screen ensures your sensitive information remain confidential',
                style: TextStyle(fontSize: 16),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

Try It Out

• Launch your app.
• Switch to another app or return to the home screen.
• Open the app switcher — you’ll see the blurred overlay.
• Return to your app — the blur will disappear. ✅

Bonus Ideas

• 💼 Show your logo or a security icon on the overlay.
• 🌓 Match the overlay with light/dark mode themes.
• 🛡 Combine with platform-specific flags like FLAG_SECURE on Android and isScreenCaptured detection on iOS to block screenshots or respond to screen recording.

Final Thoughts

This is one small features that can make a meaningful difference — especially in apps that handle financial, medical, personal data or anything that feels sensitive.

💡 Implementing this feature helps prevent sensitive information from being exposed in app previews, adding a subtle but meaningful layer of privacy that users will appreciate.

A simple addition that makes a big impact on creating a safer and more trustworthy user experience. If you’re developing a Flutter-based application and want to implement security features like this, LOGIQUE is here to help. We are a company that provides Flutter app development services that are secure, responsive, and tailored to your business needs. Contact us today!