Optimizing Mobile App Load Time
Learn to optimize mobile app load times, including cold vs. warm start, lazy loading, and asset bundling techniques for improved performance.
Emma, a regular user of our app, taps the icon, eager to get started. But instead of the smooth experience she expects, she faces the app icon for several seconds before anything appears. Those initial seconds feel like an eternity, testing her patience. Frustrated, Emma quits and tries a competitor’s app instead.
Emma’s experience isn’t unique. It’s a common scenario that directly impacts an app’s success. Even slight delays cause significant user frustration, higher abandonment rates, and lower retention.
This lesson explores the practical solutions to this exact problem. We will first cover the high-level strategies and then dive into the specific techniques used to implement them.
To prevent users like Emma from getting frustrated, we first need to understand the different ways our app can launch. Let’s explore the two key scenarios: cold starts and warm starts.
Cold vs. warm starts
When a user launches an app, it can experience either a cold or warm start.
A cold start occurs when the app launches for the first time or after its process has been terminated, either by the user or the operating system. The app must load everything from scratch, such as assets, data, and initialization processes, because no resources are cached in the cold start. Cold starts typically take longer, often causing extended
splash screens The initial loading screens or branded visuals shown while the app is launching A warm start happens when the app is reopened after being recently closed or left running in the background. Since some resources and processes remain in memory, warm starts are much faster. This behavior is often supported by app hibernation, where the app retains its state and resources. It’s important to note that this capability applies only to apps that support background activity, and its implementation can vary across platforms.
The following diagram illustrates the key differences between these two launch scenarios:
Understanding the difference between a cold and a warm start is the critical first step. Let’s explore the core strategies we can use to make both launch scenarios as fast as possible.
Strategies to optimize load time
Most performance strategies involve a few fundamental principles. By understanding them, we can make smart decisions across our entire app. This section covers the essential strategies that serve as the backbone of performance optimization.
Prioritize and defer tasks
The most important principle is to do the absolute minimum work required to present an interactive UI to the user. All non-essential tasks should be postponed until after ...