Profile pictures that must be exactly 400 × 400, a marketplace that rejects anything over 2000 pixels, a website hero that needs to be 1200 wide — resizing is the image job everyone meets. Drop a photo in, type the size, download the result. Your image is decoded and redrawn by your own browser; it never leaves your device.
Aspect ratio: the lock that saves photos
An image's aspect ratio is its width divided by its height. Change one side without the other and faces stretch — the classic resized-photo mistake. With the lock on (the default), typing a width works out the height for you, so the picture can grow or shrink but never distort. Turn the lock off only when a site demands exact dimensions that don't match your photo's shape — and consider cropping instead, which fills the frame without stretching anything.
Enlarging: honest limits
Shrinking an image discards detail gracefully; enlarging invents it. Doubling a photo's pixels makes a bigger file, not a sharper one — browsers smooth the result, which looks acceptable for modest increases (up to about 150%) and progressively softer beyond that. If a form demands a minimum size and your photo is smaller, the resized file will satisfy the form; it cannot add detail that wasn't captured.
Which format?
Keep the original format unless you have a reason to switch. JPG is smallest for photos, PNG preserves transparency and crisp edges, WebP is smaller still for the same quality and is accepted by all modern browsers and most platforms now.
Worked example
Use the sample photo (1200 × 800). Set width to 600 with the lock on: the height follows to 400 automatically, and the download is a true 600 × 400 image — check its properties and see. Then unlock the ratio, set 600 × 600, and notice the stretch; that's what the lock protects you from.
How to use this tool
- Drop your image onto the box (or use the sample photo).
- Type a width or height — with the lock on, the other side follows.
- …or pick a quick percentage (50% halves both sides).
- Choose an output format, or keep the original.
- Press Resize image and download the result.
Common sizes worth knowing
Website hero images: 1600–2000 px wide. Blog and social shares: 1200 × 630. Profile photos: 400 × 400 to 800 × 800 square. Email newsletters: 600–700 px wide (they're displayed small even on big screens). Passports and ID photos have regulated sizes per country — use the Crop tool with its aspect presets and your authority's official dimensions.