I have been working to migrate an Osclass classified website to Custom made Laravel ad listing E-commerce solution for 2 weeks. It has more than 1,20,000 uncompressed preview and thumbline images that cause the slow page load issue. I was desperately seeking a minimal solution to resize thousands of images in multiple folders.
My OS is windows 10. After few hours of google search, got a few applications that serves my partial requirements but xnview (FREEWARE) an awesome application for bulk image resizing that fulfill my needs.

I need to unchanged the Images folder staructure and keep image extension same as source. I could do this by using this application but an afficient way.

It has multiple CPU core support that makes it blazing fast image resizing tool.

So, let’s start. You may select single image (Add Files) of multiple folders (Add folder) with images and click Next.

Fix your desired setup and click Next

Don’t forget to check the keep folder structure in order to keep the previous folder structure same as source.
Now click Convert and That’s it !!!