Showing a preview before uploading gives users immediate confidence that they selected the right file, dramatically reducing mistakes and re-uploads. As the creator of CoreUI with Angular development experience since 2014, I include image preview in every avatar upload or gallery feature in CoreUI Angular templates. The browser’s FileReader API reads the selected file as a Data URL and Angular’s change detection updates the preview image source reactively. This requires no libraries — just the native File API and a reactive component property.