10 Tips to Reduce App Startup Time

Table of Contents

Want to make your app load faster? Here’s a quick guide to improve app startup times for sports and fitness apps:

Efficient Asset Loading: Use lazy loading to prioritize critical assets and defer non-essential ones.
Delay Non-Critical Tasks: Push back analytics, feature flags, and background services until after launch.
Keep the Main Thread Free: Offload heavy tasks (e.g., database queries, network calls) to background threads.
Use Loading Screens: Display skeleton screens to improve perceived performance.
Limit Third-Party Code: Audit libraries, remove unused ones, and delay non-essential SDKs.
Track Startup Metrics: Monitor metrics like Time to First Frame and optimize based on data.
Lower Resource Usage: Compress assets, minify code, and remove unused resources.
Simplify First Screen: Reduce UI complexity and preload critical elements.
Optimize Network Calls: Compress payloads, cache responses, and prioritize essential API requests.
Store Data Locally: Use memory and disk caching for instant access to frequently used data.

Quick Fix: Start by deferring heavy tasks and reducing the load on your app's main thread. Use tools like async/await and dispatch queues to streamline performance.

These steps ensure users get quick access to workouts, live stats, and wearable sync without delays. Focus on speed, simplicity, and responsiveness.

Reducing App Launch Times: From Diagnostics to Optimization

What Slows Down App Startup

App launches can be divided into three types: cold, warm, and hot. Each type affects startup time in a different way.

Launch Types and Their Impact

Cold Launch: Everything - code, assets, and configurations - loads from scratch. This takes the most time.
Warm Launch: The app reuses resources still in memory after a recent close, speeding things up.
Hot Launch: The app resumes from the background with minimal setup, making it the fastest.

Common Startup Bottlenecks

Here are some common culprits behind slow app startups:

Heavy Initialization: Tasks like database setup, loading analytics SDKs, or rendering complex UI elements can drag things down.
Main-Thread Congestion: When resource loads or computations block the main thread, it delays user interaction.
Resource Dependencies: Framework initializations, third-party modules, or parsing configurations can create delays.

Measuring Startup Performance

To identify what's slowing things down, focus on these metrics:

Time to First Frame: How long it takes for the first UI element to appear.
Main-Thread Blocking: Tasks that prevent the app from responding to user input.
Initial Memory Usage: Excessive memory demands can lead to paging and slowdowns.

Once you understand launch types, bottlenecks, and key metrics, you can start optimizing - like improving how assets are loaded.

1. Load Assets More Efficiently

Once you've assessed your startup metrics, focus on improving how your app loads assets. Start by using lazy loading to delay non-essential items - like large images, videos, or bulk data - until after the initial user interface is visible. By prioritizing only the critical assets needed for the first screen, you can significantly reduce both cold and warm startup times.

Additionally, ensure that all deferred tasks run off the main thread. This approach helps maintain a smooth and responsive UI during the loading process.

2. Push Back Non-Critical Tasks

Delay tasks that aren’t essential for your app’s initial screen to speed up startup time.

Here are some ways to prioritize effectively:

Analytics: Set up basic analytics during launch, but hold off on full configuration and syncing historical data until after the UI is visible.
Feature Flags: Load only the necessary feature flags at startup, and retrieve the rest in the background after launch.
Data Prefetching: Focus on fetching only the critical data needed for the first screen. Stream additional content as users engage with the app.
Other Services: Delay tasks like push-notification registration, enabling location services, or setting up social SDKs until after the app becomes interactive.

To make this work smoothly, use tools like lazy properties, background queues, dispatch groups, and progressive loading. These approaches help shift tasks off the main thread, ensuring the UI stays responsive.

3. Keep Main Thread Clear

To maintain a responsive UI, it's crucial to free up the main thread by handling heavy tasks elsewhere.

Common Heavy Operations

Some operations that can bog down the main thread include:

Database queries
File read/write tasks
CPU-heavy processes like parsing or complex calculations
Image manipulation
Network calls

How to Offload Tasks

Dispatch Queues
- Use background queues for tasks that consume significant resources.
- Assign appropriate Quality of Service (QoS) levels based on task importance.
- Only bring results back to the main thread when absolutely necessary.
Batch Processing
- Group similar tasks together for efficiency.
- Break data into smaller chunks for processing.
- Update the UI only after completing a meaningful portion of the work.
Task Prioritization
- Use operation queues to manage tasks with varying priority levels.
- Set dependencies between operations to ensure proper sequencing.
- Cancel tasks with low priority if they take too long or are no longer needed.

Key Practices for Smooth Performance

Use performance profiling tools to monitor main thread activity.
Leverage async/await for clearer and more organized concurrency.
Handle errors gracefully in background operations to avoid crashes or unresponsive behavior.
Cache results of heavy computations to prevent redundant processing.
Release resources as soon as they're no longer needed to avoid memory issues.
Load resources in stages: start with essential elements (like UI and core data), then move to secondary items (preferences, cache), and finally optional ones (analytics, feature flags).

Next up: learn how to use loading screens effectively to improve perceived performance.

4. Show Loading Screens

Use skeleton screens as placeholders to mimic your layout while content loads. These lightweight visuals help set user expectations and make the app feel faster.

5. Reduce Third-Party Code

Cut down your app's startup load by limiting the use of third-party code.

Third-party libraries can slow down your app's startup time. Here's how to address that:

Audit Your External Libraries
Go through all the external libraries in your app. Get rid of unused packages, and where possible, replace small utilities with native code.

Postpone Nonessential SDK Initialization

Delay analytics setup until after the first screen is displayed.
Load social SDKs only when a user interacts with sharing features.
Import custom UI components only when they’re needed.

For essential SDKs, opt for modular or lightweight versions and include only the parts you actually need.

Always measure how long each dependency takes to initialize. If any exceed your app's startup time goals, consider replacing them.

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6. Track Startup Metrics

Once you've streamlined tasks and reduced external code, it's time to measure the impact by keeping an eye on startup metrics.

Monitoring startup metrics helps you identify any bottlenecks. Define your app's key launch events and gather timing data for every stage of the initialization process. Use built-in tools or lightweight libraries to measure things like initialization times, resource load durations, and the time it takes for users to start interacting with your app.

Add custom markers or logs to critical parts of your code for better tracking. Automate this monitoring with each release to quickly catch any performance regressions. Regularly review your metrics - look for trends, compare different releases, and set clear performance goals to keep improving.

7. Lower Resource Usage

Reducing runtime resource demands can significantly speed up your app's startup process. Here are some practical ways to achieve this:

Use vector assets like SVG (on Android) or PDF (on iOS) for icons and simple graphics. These formats keep file sizes smaller.
Compress images with formats like WebP (for Android) and HEIF (for iOS) to save memory and storage space.
Eliminate unused images, fonts, and other resources from your build to reduce the size of your app's binary.
Minify and tree-shake your code to remove debug symbols and unused code, which helps shrink the startup footprint.
Use tools like Xcode Instruments or Android Studio Profiler to monitor CPU and memory usage during launch. This will help you identify the biggest resource consumers.

8. Simplify First Screen Load

Once you've reduced resource usage, focus on making your app's initial screen load faster. Use your Time to First Frame metrics to identify which UI elements can be optimized or delayed.

Here are some ways to streamline the first screen:

Reduce view hierarchy depth: Avoid deeply nested layouts and view groups to speed up rendering.
Pre-render critical UI components: Compile key elements ahead of time instead of inflating them during runtime.
Delay custom fonts and nonessential styles: Load these only after the user interacts with the app.
Postpone heavy animations and transitions: Disable or defer them until after the app has launched.

These steps ensure the first screen loads quickly while maintaining a smooth experience.

9. Speed Up Network Calls

Network requests can often slow down app startup. To improve launch times, focus on optimizing initial API calls.

Start by prioritizing API requests needed for the first screen. Delay nonessential calls until after the app has launched, and limit the number of simultaneous requests to avoid overloading the system.

Use GZIP compression, set appropriate cache headers, and choose binary formats like Protocol Buffers instead of JSON to reduce payload size and parsing time.

Cache API responses using TTL headers, and update them in the background to ensure users get the latest data without delays. Display cached data immediately, then fetch updates in the background to refresh the UI seamlessly.

Request only the fields you need, paginate large datasets, and compress media files before sending them over the network.

Set timeouts between 10–15 seconds, implement retries with exponential backoff, and rely on cached data when offline.

For real-time updates, switch to WebSockets to minimize HTTP overhead.

Once network calls are optimized, consider leveraging local data storage for further performance improvements.

10. Store Data Locally

Cut down startup delays by using local caching to serve stored data immediately. This method works alongside network optimizations to reduce unnecessary back-and-forth requests during app launch.

Memory cache: Use an LRU (Least Recently Used) cache for essential startup data, allowing for instant access.
Disk cache: Save items like configuration files, user preferences, tokens, and frequently used API responses on disk for quick retrieval when needed.
Background refresh: Set up TTL (Time-to-Live) or version checks, and use background-fetch APIs to update outdated cache after launch without interrupting the user experience.

To make this process even smoother, prewarm caches in the background, compress stored data, and opt for binary formats like Protobuf for faster parsing. Always handle I/O errors in a way that prevents crashes or disruptions.

For sensitive data, make sure to encrypt it with secure-storage APIs provided by the platform.

Finally, monitor cache hit rates alongside other startup metrics to see how much local storage improves launch performance.

Pros and Cons of Each Method

Here’s a breakdown of the advantages and drawbacks of various optimization techniques:

Technique	Pros	Cons
Load Assets More Efficiently	• Improves performance quickly • No backend changes required • Reduces memory usage	• Requires asset reorganization • May involve extensive code refactoring • Time-intensive initial setup
Push Back Non‑Critical Tasks	• Quick to implement • Immediate startup improvement	• Risk of delaying key features • Requires careful task prioritization • May impact analytics timing
Keep Main Thread Clear	• Enhances UI responsiveness • Provides a better user experience • Reduces ANR (Application Not Responding) issues or crashes	• Complex threading management • Risk of race conditions • More development complexity
Show Loading Screens	• Improves perceived performance • Easy to implement	• Doesn’t solve underlying issues • Overuse can frustrate users • Requires design resources
Reduce Third‑Party Code	• Decreases app size • Improves control over performance • Reduces dependencies	• May require rebuilding existing functionality • Increases maintenance workload • Higher development costs
Track Startup Metrics	• Enables data-driven improvements • Offers clear performance insights	• Adds monitoring overhead • Involves storage and transmission costs • Requires setup and maintenance
Lower Resource Usage	• Enhances overall performance • Reduces battery consumption • Provides a smoother experience	• Might limit available features • Demands optimization expertise • Needs ongoing maintenance
Simplify First Screen Load	• Provides instant visual feedback • Speeds up initial rendering • Improves perceived startup speed	• Limits initial functionality • Complicates navigation logic • May involve UI/UX trade-offs
Speed Up Network Calls	• Faster data access • Reduces server load • Improves offline handling	• Requires backend coordination • Complex cache management • Challenges with data synchronization
Store Data Locally	• Enables instant data access • Supports offline functionality • Reduces server dependency	• Limited by storage capacity • Risks of outdated data • Raises security concerns

For sports and fitness apps, focus on efficient asset loading and keeping the main thread free to ensure smooth workout tracking and live stats. Features like social sharing or other non-essential tasks can be deferred until after launch.

Use these trade-offs as a guide when shaping your optimization strategy.

Summary

Optimizing app startup time is essential for sports and fitness apps. By focusing on efficient asset loading, offloading non-critical tasks, managing the main thread effectively, improving network calls, and using local caching, developers can ensure quick access to workouts, user preferences, and wearable data.

For apps that track workouts in real-time and integrate with wearable devices, delivering instant access to workout history and user preferences is key to maintaining smooth performance.

2V Modules focuses on performance-driven development, efficient data management, seamless wearable integration, and user-friendly design to speed up app startup.

"Their level of integration and their willingness to build an awesome product was outstanding." - Executive, High End