About the Image Resizer
Set a width, a height or both — or scale by a percentage — to resize one image or a whole batch. Proportions are kept unless you untick the option, so photos are never stretched.
How does the Image Resizer work?
Large reductions are done in several halving steps, which keeps fine detail sharper than a single resize.
Example
A 4032 × 3024 phone photo resized to 1600 px wide becomes 1600 × 1200 with the proportions kept — typically dropping from about 3 MB to a few hundred KB.