Compress vs Resize Images: Which Reduces File Size?

What is the difference between compressing and resizing?

Compression changes how pixels are encoded. In PDF Logic, JPG and WebP use adjustable quality, while PNG uses lossless encoding and optimization. Resizing changes the number of pixels. Cropping removes pixels outside a selected frame. Each can reduce bytes, but none guarantees a particular file size for every source.

Scroll the table to compare all columns.

Choose the resize mode deliberately

• Fit: keeps the whole image within the requested bounds. When proportions differ, one output dimension can be smaller than the box.
• Fit with padding: keeps the whole image and adds the chosen background so the output has the exact requested width and height.
• Fill: crops edges to fill the requested dimensions when no enlargement is needed or enlargement is enabled. Set the focal position, then inspect each image.
• Stretch: changes proportions to use the requested dimensions when no enlargement is needed or enlargement is enabled.

Enlargement is off by default, so Fill and Stretch stop at source dimensions when the requested result would otherwise enlarge the image. Fit with padding still creates the exact requested canvas. Increasing dimensions adds pixels but cannot restore source detail. The browser’s canvas model defines how images are drawn into destination rectangles; see the WHATWG canvas drawImage() specification for the underlying scaling operation.

Use the smallest necessary change

1. Record the destination’s accepted format, maximum bytes, and required pixel dimensions.
2. If dimensions are too large, open Resize images and choose Fit, Fit with padding, Fill, or Stretch. Review whether the complete subject remains visible.
3. If framing includes unneeded pixels, use Crop images. Batch framing scales across different source sizes, so inspect every crop.
4. If dimensions are already suitable, open Compress images. Start at a useful quality, compare Original and Output at 100%, and lower quality only as needed.
5. For a hard byte limit, enter the target. PDF Logic measures the encoded output and reports when the selected quality floor cannot reach it. The target does not silently change dimensions.

Why can the result miss a size target?

Encoded size depends on image content, format, dimensions, and settings. Fine texture and noise can require more data than flat graphics. PNG has no lossy quality slider in this workflow, and a JPG or WebP quality floor can prevent further reduction. An already smaller original may be retained, including its metadata, unless you enable “Always remove metadata” to force re-encoding.

Use the actual result rather than a predicted percentage. Check text, edges, gradients, faces, and transparency at the intended display size. If a result remains too large, reduce dimensions or crop only when the destination permits those changes.

For format trade-offs, read JPG vs PNG vs WebP vs AVIF. For the complete batch and privacy workflow, see Edit images in your browser.