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March 19, 2024

Angular Trackby

March 19, 2024
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Angular Trackby is a feature in the Angular framework that allows developers to optimize the rendering of lists in Angular applications. By assigning a unique identifier to each item in a list, Angular Trackby enables efficient and smooth updates to the UI when items are added, removed, or modified.


In Angular applications, it is common to display lists of data, such as user profiles, products, or blog posts. When these lists change due to user interaction or data updates, Angular needs to re-render the entire list to reflect the changes. However, this process can be computationally expensive, especially when dealing with large lists or complex UI elements.

Angular Trackby addresses this issue by providing a mechanism to track and uniquely identify each item in a list. Instead of relying solely on the position or order of the items, Angular Trackby adds stability to the UI rendering process by associating an identifier with each item. This identifier remains consistent even when the list is dynamically modified, ensuring efficient rendering and minimizing unnecessary DOM manipulations.


  1. Enhanced Performance: By using Angular Trackby, developers can significantly improve the performance of their Angular applications. The ability to identify unique items helps Angular avoid unnecessary re-rendering of the entire list, leading to smoother and faster UI updates.
  2. More Efficient Memory Management: When a list is modified without using Angular Trackby, the previous DOM elements are often destroyed and new ones are created. This can result in a higher memory footprint and performance degradation. With Angular Trackby, only the necessary changes are made to the DOM, reducing memory usage and increasing overall application efficiency.
  3. Seamless User Experience: Angular Trackby ensures that the user’s interactions with lists are seamless and intuitive. Whether it is adding an item, deleting an item, or modifying an item, the user can expect instantaneous updates without any visible lag or flickering.


Angular Trackby is particularly useful in scenariOS where lists are frequently updated or contain complex UI elements. Here are some common applications:

  1. E-commerce Websites: When displaying product catalogs or shopping carts, Angular Trackby can provide a smooth shopping experience by promptly updating the UI as users add or remove items.
  2. Social Media Feeds: Platforms that rely on real-time updates, like Twitter or Facebook, can leverage Angular Trackby to efficiently render and refresh the feed, ensuring that the latest posts are displayed promptly.
  3. Data-driven Applications: Angular Trackby can be beneficial in applications that display data from external sources, such as data analytics or financial tools. It allows for swift updates to data visualizations, charts, and tables.


Angular Trackby is a powerful feature of the Angular framework that optimizes the rendering of lists in Angular applications. By assigning unique identifiers to items in a list, it offers enhanced performance, efficient memory management, and a seamless user experience. With its ability to track and update only the necessary changes, Angular Trackby contributes to the overall performance and speed of Angular applications, particularly when dealing with dynamic lists or complex UI elements.

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