Resize images online
An image resizer changes the pixel dimensions of a picture: how many pixels wide and how many pixels tall it is. You might need a smaller photo for an email attachment or a website form, a specific size for a social post or a blog header, or a lighter logo for a document. This tool does it in a few clicks without installing anything.
Everything happens on your device. Your browser opens the file, draws it at the new size and saves the result. Your image is not uploaded to our servers, so it works for private photos and documents too.
What does resizing an image mean?
A digital image is a grid of pixels. A 4000 × 3000 photo has 4,000 columns and 3,000 rows, 12 million pixels in total. Resizing to 1200 × 900 creates a new, smaller grid and works out the colour of each new pixel from the pixels around it in the original. The picture looks the same, just with fewer pixels, and the file is usually much smaller.
Resizing in the other direction, making an image larger, spreads the existing detail over more pixels. It can't invent detail that was never captured, so enlarged images look softer. The tool warns you when you choose a size larger than the original.
How to resize an image
- Choose an image. Drag it onto the upload area, or click Upload Image to pick a JPG, PNG, WebP or GIF file. You'll see its dimensions and file size.
- Pick the new size. Type the width or height you want in pixels. With Keep aspect ratio on, the other side is worked out for you. Percentages and common sizes are under More options.
- Choose a format. The tool keeps your image's format where it can. To save as JPG, PNG or WebP, or to set the quality, open More options.
- Resize and download. Press Resize Image, check the before and after sizes, then press Download Image. The file is named with its new size, for example
photo-1200x800.webp.
Resize vs compress vs change format
These three are often mixed up, but they change different things:
- Resizing changes the pixel dimensions. It's the most effective way to shrink a large photo, because the file holds far fewer pixels.
- Compressing keeps the dimensions but stores the pixels more efficiently. JPG and WebP do this with a quality setting: lower quality means a smaller file and more visible artefacts.
- Changing format re-saves the image in a different file type. JPG suits photos, PNG suits logos, screenshots and images with transparency, and WebP often gives smaller files than both.
This tool resizes and lets you choose the format and quality at the same time. A smaller size doesn't always mean a smaller file: a photo saved as PNG can be larger than the original JPG, so the tool shows both file sizes before you download.
Aspect ratio explained
The aspect ratio is the relationship between width and height. A 1920 × 1080 image is 16:9, a 1080 × 1080 image is 1:1, and many camera photos are 3:2 or 4:3. Keep the ratio the same and the picture keeps its shape. Change it and something has to give.
Keep aspect ratio is on by default: type a width and the height follows. If you turn it off or pick a size with a different shape, choose between Crop, which scales the image to cover the new size and trims the edges evenly, and Stretch, which keeps the whole picture but distorts it.
Common image dimensions
These are widely used sizes, offered as quick starting points. They are not official requirements: platforms change their recommendations, so check the current guidance of the site you're uploading to.
| Use | Size (px) |
|---|---|
| Square post | 1080 × 1080 |
| Portrait post | 1080 × 1350 |
| Link / share image | 1200 × 630 |
| Story / vertical | 1080 × 1920 |
| Full-width hero | 1920 × 1080 |
| Blog image | 1200 × 675 |
| Thumbnail | 600 × 400 |
| 1280 × 720 | 1280 × 720 |
| 1600 × 900 | 1600 × 900 |
| 1200 × 800 | 1200 × 800 |
| 800 × 600 | 800 × 600 |
Adding a logo to an invoice? The invoice generator accepts PNG or JPG logos up to 1 MB, and a logo around 600 px wide is plenty for a crisp PDF. The same logo works on a quote too.
Supported formats
- Upload: JPG (JPEG), PNG, WebP and GIF, up to 40 MB and 50 megapixels.
- Download: JPG, PNG or WebP. WebP is offered when your browser can save it.
- Transparency: PNG and WebP keep transparent areas. JPG has no transparency, so they're filled with white.
- Animation: animated GIF, PNG and WebP files are resized as a still image of the first frame.
Looking for something else? Browse all free KaroDesk tools.