Two different tools, two different problems
Image resizing and image compression are often confused because both reduce file size. But they solve different problems, and using the wrong one can either cost you quality or leave significant file size on the table.
Resizing changes the pixel dimensions of an image. A 4000×3000 photo resized to 800×600 has fewer pixels — and therefore a smaller file — but the quality per pixel is unchanged.
Compressing reduces the amount of data used to represent the same pixel dimensions. A 800×600 image at 80% quality takes less storage than the same image at 100% quality, but the displayed size stays the same.
Use Image Resizer to change dimensions and Image Compressor to reduce file size at the same dimensions.
When to resize
Resize when the image is larger than it will ever be displayed. This is the most common scenario:
- A photograph from a camera is 5000px wide; your website’s content column is 1200px wide. Resizing down eliminates 90%+ of pixel data that was never going to be displayed.
- A product image needs to appear as a 400×400 thumbnail in a grid. Serving the original 2000×2000 version and scaling it down in CSS is four times more data than necessary.
- A user-uploaded image needs to fit within a specific canvas for a social media post or printout.
Resizing is irreversible — you can’t recover pixels that have been discarded. Always keep the original and resize to a copy.
When to compress
Compress when the image is already at the right dimensions but still too large. Common scenarios:
- The image has been resized correctly but the JPEG quality is set too high for web use (quality 100 is rarely necessary; quality 80-85 is visually identical for most images).
- The image is a PNG file with no transparency that could be smaller as a JPEG.
- The image was exported from a design tool with metadata and color profiles included that add size without affecting display.
Compression is the right choice when you need the image to display at exactly the dimensions it’s saved at but want to reduce the bytes transferred to the browser.
The optimal order: resize first, then compress
When you need both — and you often do — resize first, then compress. This is more efficient because:
- Compressing a large image takes more processing time than compressing a smaller one.
- The compression algorithm has less data to work with after resizing, producing smaller output files.
- Artifacts from lossy compression are less visible at smaller dimensions.
A workflow: receive a 6MB camera photo → resize to 1200px wide → compress at quality 82 → result is typically 80-150KB, down from 6MB.
Format choice affects both size and quality
Sometimes the best size reduction comes from switching formats rather than adjusting quality settings.
- Convert a PNG photograph to JPEG and it will often be 60-80% smaller with no visible difference (as long as transparency isn’t needed).
- Convert a JPEG or PNG to WebP and you typically get 25-35% additional savings at the same visual quality.
Use Image Format Converter when format conversion would produce a better result than compression alone.
Quick reference
| Situation | Tool to use |
|---|---|
| Image is too wide/tall for the display context | Image Resizer |
| Image is right size but file is too large | Image Compressor |
| Image needs both dimension and size reduction | Resize first, then compress |
| Wrong format for the use case | Image Format Converter |
| Need to check a pixel’s color value | Image Color Picker |
When in doubt, resize to the target display size first. You’ll usually find that resizing alone handles the bulk of the file size reduction, with compression taking care of the rest.