Comparing statically imported image file vs. path string for NextJS Image component

Question

I am developing a statically exported website in NextJS (13.5.6). From the NextJS documentation on the Image component, I understand that the "src" parameter can either accept a statically imported image file or a path string.

My question is the following: is it more efficient to import images in NextJS using a statically imported image file or to use a path string that points to the "public" folder?

To be precise, what I mean by statically imported image file is based on the following code:

import myImage from '../../public/my-image.jpg';
<Image src={myImage} alt="mi" />

And what I mean by path string that points to the "public" folder is based on the following code as well as detailed here in the NextJS docs:

<Image src="/my-image.jpg" alt="mi" width="64" height="64" />

The reason for my question is that I noticed when using a statically imported image file, the build process would create two copies of the image in the "dist" directory as follows:

1. dist\apps\myApp.next_next\static\media\my-image.jpg
2. dist\apps\myApp.next\my-image.jpg

However, if I use a path string, the build process only creates a single copy of the image in "dist\apps\myApp.next\my-image.jpg". As a result, it seems that using a path string to the "public" folder is more space efficient.

Thanks!

Answer 1

In Next.js, when you use a statically imported image file, it enables the Next.js image optimization system. This system provides benefits like lazy loading, responsive sizing, and optimized image formats based on the browser. The build process will copy the image to the .next/static/media directory with a content hash in the filename to enable efficient caching.

On the other hand, when you use a path string that points to the "public" folder, Next.js will serve the image directly without any processing or copying into the build directory. This approach can indeed be more space-efficient since it doesn't create additional copies of the image.

To summarize, using statically imported image files allows for optimization features provided by Next.js, while using a path string to serve images directly from the "public" folder is more space-efficient but forgoes these optimizations.

If space efficiency is a priority and you do not need the image optimization features, or if your images are already optimized and you manage responsive behavior manually, then using the path string method may be more suitable for your use case.