Mixed image batches are rarely uniform. Portraits, landscapes, squares, and screenshots can all arrive in the same folder. The safest resize rule depends on whether you need a boundary, a fixed canvas, or identical output dimensions.
Fit inside a boundary
“Fit inside” preserves every image’s aspect ratio and scales it until both dimensions are within your target. A 4000 × 3000 photo fitted inside 1600 × 1600 becomes 1600 × 1200. A portrait image uses the same rule but reaches the height limit first.
Use this mode when you want to limit size without cropping or stretching. The outputs will not all have identical dimensions, but their proportions remain correct.
Fill a fixed size
“Fill” preserves aspect ratio but crops the overflow. A wide image placed into a square keeps its geometry; pixels at the sides are removed. A portrait loses pixels at the top and bottom.
This is useful for product tiles, avatars, and grids that need identical boxes. A centered crop assumes the subject is near the center, so review images with off-center composition.
Use exact dimensions carefully
Exact resizing draws every image to the width and height you enter. It guarantees identical dimensions but can stretch or squash the image when the original ratio differs.
Exact dimensions make sense for assets that already share the target ratio, or when a specification explicitly permits distortion. Otherwise, fit or fill is usually safer.
Prevent accidental enlargement
Upscaling makes a file larger in pixel dimensions but cannot restore detail that was never captured. An “only shrink” option protects small sources from enlargement while larger images are reduced normally.
For genuinely low-resolution sources, ordinary interpolation and AI upscaling are different tools. The Windows app has a separate local Real-ESRGAN workflow; the browser resizer does not generate missing detail with AI.
Keep the rule visible
Before running a large queue, test one landscape and one portrait image. Confirm the dimensions and check whether fill mode removes important content. A batch rule is most useful when everyone can describe it clearly: “fit inside 1600 × 1600,” not simply “make them 1600.”
The online batch resizer includes pixel and percentage rules, an only-shrink setting, and size presets. For a specific catalog workflow, follow resizing product images for a consistent grid. When the subject needs a different position in each photo, fine-tune individual crops before resizing.