Lazy loading, while beneficial for improving initial load times and reducing bandwidth usage, can lead to performance issues in several scenarios:
**1. Overuse or Excessive Lazy Loading
When too many resources (such as images or components) are lazy loaded indiscriminately, it can cause delays in loading critical content, negatively impacting user experience and metrics like Largest Contentful Paint (LCP). For example, a WordPress test showed that disabling lazy loading on archive pages improved LCP significantly, indicating that excessive lazy loading can slow down perceived load speed[1]. Over-aggressive lazy loading leads to increased latency as content is fetched on demand, which may defeat its purpose[6].
**2. Lazy Loading and Hydration in JavaScript Frameworks
In modern JavaScript applications, lazy loading can conflict with the hydration process, where the framework needs to make components interactive by attaching event listeners and restoring state. Since hydration requires eagerly walking the component tree, lazy loading components that are part of the initial render tree often results in multiple HTTP requests and redundant work, negating the benefits of lazy loading. This makes lazy loading more effective only for components not initially rendered, such as those loaded on route changes. Managing this complexity is difficult and often requires custom automation[2].
**3. Latency and User Interaction Delays
Lazy loading defers loading until the resource is needed, which introduces latency when the user actually requests the content (e.g., scrolling to an image or clicking a button). This delay can degrade real-time responsiveness, especially on slow or unreliable networks. It can also cause layout shifts or visible loading placeholders that harm user experience[6][4].
**4. Complexity and Maintenance Overhead
Implementing lazy loading requires careful planning about which resources to load eagerly or lazily, increasing code complexity and maintenance effort. Developers must predict user behavior to optimize loading, which is challenging for large or dynamic applications. Without proper handling, lazy loading can cause unnecessary network requests or fail to preload resources that will soon be needed[2][6].
**5. Inappropriate Use Cases
Lazy loading is not suitable for critical resources that are essential for the initial render or user interaction. For example, images or scripts above the fold should be eagerly loaded to avoid delaying the first meaningful paint. Lazy loading is better reserved for offscreen images, below-the-fold content, or components loaded on demand (e.g., after navigation or user action)[4][5].
In summary, lazy loading leads to performance issues when it is overused, applied to critical resources, conflicts with hydration in JavaScript frameworks, or introduces latency that harms user experience. Properly balancing lazy and eager loading based on resource criticality and user behavior is essential to avoid these pitfalls.
Citations:
[1] https://web.dev/articles/lcp-lazy-loading
[2] https://www.builder.io/blog/the-challenges-of-lazy-loading-in-javascript
[3] https://stackoverflow.com/questions/878069/to-lazy-load-or-not-in-effort-to-improve-performance
[4] https://hackernoon.com/dont-be-lazy-3-problems-with-lazy-loading-and-when-to-use-eager-loading-qq1d34cl
[5] https://developer.mozilla.org/en-US/docs/Web/Performance/Guides/Lazy_loading
[6] https://dev.to/aws-builders/lazy-loading-vs-write-through-a-guide-to-performance-optimization-28ka
[7] https://www.reddit.com/r/web_design/comments/ootcl1/the_performance_effects_of_too_much_lazyloading/
[8] https://developer.mozilla.org/en-US/docs/Web/Performance/Lazy_loading
[9] https://teamupdraft.com/blog/how-does-lazy-loading-improve-user-experience/