Percentage resizing is useful when you want every source image reduced by the same proportion. It avoids choosing one fixed width that may affect a portrait and a landscape photo very differently.
Percentage Image Resizer scales both dimensions from the original image. The percentage is a dimension multiplier, not a promised reduction in file bytes.
Half the width is not half the area
A 1200 by 800 source at 50% becomes 600 by 400. Its pixel area falls from 960,000 to 240,000, which is one quarter of the original area.
That does not guarantee a file one quarter as large. Compression, noise, transparency and the chosen codec all affect the encoded bytes. Read the file size reported after processing rather than estimating it from the percentage alone.
At 100%, the dimensions stay the same, but the tool still reencodes the pixels. Original metadata and colour profiles are not copied into the output.
Use the original for each attempt
Reducing an already reduced copy can compound softness. Keep the source and make another percentage choice from it instead of repeatedly shrinking earlier downloads.
An increase above 100% enlarges the canvas dimensions. It does not add real photographic detail. Text and thin lines can become noticeably soft after enlargement.
Batch processing applies the selected percentage separately to each image. A 50% reduction therefore preserves their differing sizes and ratios rather than turning them into a uniform catalogue grid.
Choose a fixed size resizer when the destination requires one exact width. Choose percentage scaling when a proportional reduction is the actual goal. In either case, inspect a face, a logo edge or a small text label at normal viewing size before accepting the download.