How to resize an image without uploading it
Change the pixel size of a JPG, PNG or WebP image in the browser, and know what that does to quality.
Resizing changes how many pixels wide and tall an image is. It is separate from compression, which changes how those pixels are stored. A photo prepared for a website is often both smaller in pixels and saved at a moderate JPEG or WebP quality.
Keep the aspect ratio
The aspect ratio is width divided by height. If a picture is 4000 by 3000 pixels, the ratio is 4:3. Locking the ratio means you type one side and the other side follows. Unlock it only when the frame itself must change, because the subject will stretch.
What happens to quality
- Shrinking discards pixels. A 4000-pixel photo becomes a 1600-pixel photo; the extra detail is gone.
- Enlarging spreads the same detail over more pixels. Edges look softer. It cannot recover a sharper original.
- JPEG and WebP then encode that result at a quality you choose. PNG keeps every pixel and usually makes a larger file.
The RS Labs image resizer draws the picture on a canvas in your browser and downloads the new file from there. The image is not uploaded.