Transparent PNG or White Background: Which Should You Save?
They look identical on a white page and behave completely differently everywhere else. Here is when to use each.
On a white web page, a transparent PNG and a white-background JPG look exactly the same. Put either on a coloured slide and the difference becomes obvious immediately.
Transparent PNG
The background is genuinely empty. The subject can sit on any colour, photo or video without a visible box around it. This is what you want for ads, thumbnails, presentations and anything layered.
White background
The white is baked into the pixels. It is what marketplaces require for main product images, and the file is usually smaller as a JPG, which matters for page speed.
The practical answer
Keep the transparent PNG as your master and export white-background copies from it when a marketplace asks. Going the other way, recovering transparency from a flattened white image, means cutting the subject out all over again.
One caution: PNG files are large. Compress before uploading to your own site, and consider WEBP, which supports transparency at a fraction of the size.