Read requirements and measure the source
A form can limit file bytes, dimensions or both. Record accepted formats, required width and height and maximum file size. Image information shows decoded dimensions, pixel count, aspect ratio and bytes. It does not read EXIF, GPS location or color profiles. Use a separate inspection if those properties matter for your particular task.
Many pixels do not necessarily imply many bytes. Reducing file size does not guarantee requested dimensions, and changing width does not guarantee a maximum byte count. Keep the source and prepare a copy for the specific destination, making it easier to respond later if another form requires a different composition or format.
Resolve composition before resizing
For a square destination and a wide source, decide what content must remain. Crop takes X and Y for the top-left corner and width and height for a region. The rectangle must fit inside the image. Inspect the subject before creating a cropped copy so essential information is retained.
Then resize with aspect ratio enabled. A 400 × 200 px image reduced to 100 px wide becomes 100 × 50 px. Requesting 100 × 100 without proportional sizing stretches the content. Crop a square region first for an undistorted square. Enlarging the source does not restore absent detail or automatically make its subject sharper.
Compare formats and adjust quality
Compare JPG and WebP for photos and PNG or WebP for transparent graphics, according to destination compatibility. JPG uses white in transparent areas. Changing extensions does not promise smaller files and can alter metadata or color profiles. Inspect the copy on the actual background where it will appear.
Compress image offers JPG or WebP with quality from 1 to 100. This is an encoder setting: 80 does not mean a fixed 20% byte saving or an exact measure of visual quality. An efficiently compressed source may even produce a larger copy. Always measure the downloaded output rather than estimating its size from the quality slider.
Select the finished copy by comparison
Generate trials from the source rather than repeatedly compressing a lossy copy. If quality adjustments are insufficient, reconsider whether fewer pixels meet the requirements. Compare small lettering, edges and photographs at their intended size. An acceptable thumbnail can hide defects that matter in a larger print or display.
Inspect dimensions and bytes again against your recorded requirements. Select Download before changing controls. Image operations limit files to 25 MB, 40 megapixels and 16,384 px per dimension. A phone may need a smaller source. Finish by inspecting the destination, since it can apply additional cropping or compression after you upload the locally acceptable result.
Fewer pixels without stretching
Download the 400 × 200 px image and load it into Resize image. Keep aspect ratio enabled and set width to 100. Generate and download the variant, then inspect its information to verify actual dimensions.
Width: 100 px Keep aspect ratio: enabled
The copy measures 100 × 50 px with a 2:1 ratio. File bytes depend on format and settings; no specific reduction is promised.
Compare with a 100 × 100 export without aspect ratio: its contents stretch. If a square is required, crop a square source region first and resize that copy.