How to use the image resizer
- Choose an image file. Its current dimensions appear next to the preview.
- Select “By pixels” to type an exact width or height, or “By percentage” to scale proportionally.
- Leave “Lock aspect ratio” on so the other side is calculated for you.
- Pick an output format and, for JPEG or WebP, a quality.
- Click “Resize” and then “Download”.
How it works
With the lock on, the missing side is calculated from the original ratio: newHeight = newWidth × originalHeight ÷ originalWidth, rounded to the nearest whole pixel. Percentage mode multiplies both sides by the same factor.
The image is then drawn onto a canvas of the new size with the browser's high-quality smoothing enabled. When shrinking to less than half size, the tool halves the image in steps rather than in one jump, which avoids the jagged, shimmering edges a single large downscale can produce.
Worked example
A 4000 × 3000 photo resized to a width of 1920 px with the ratio locked becomes 1920 × 1440 (1920 × 3000 ÷ 4000 = 1440). Resized to 25% instead, it becomes 1000 × 750.
Limitations
- Enlarging an image cannot add real detail; upscaled images look softer.
- Each side is limited to 16,384 px and the total to about 16.7 megapixels for browser compatibility.
- Animated images are reduced to their first frame.
- Colour profiles are converted to sRGB by the browser; wide-gamut images may shift slightly in colour.
Frequently asked questions
Will resizing reduce the file size?
Usually a lot. Halving both width and height leaves a quarter of the pixels, so the file typically shrinks to roughly a quarter or less, depending on format and quality.
What does “lock aspect ratio” do?
It keeps width and height in the same proportion as the original so faces and shapes do not get stretched. Turn it off only if you deliberately want a distorted image or an exact box size.
What size should images be for a website?
Match the largest size the image is displayed at, doubled for high-density screens. A full-width hero image rarely needs more than 2400 px across; an in-article image 1200–1600 px.
Is the original file changed?
No. The tool reads your file and creates a new one for download. The original on your device is untouched.