Image Resizer

Resizing a photo

1. Drop an image onto the box or choose a file. A line shows its name and original size in pixels, and the Width and Height fields fill in.
2. Type a new width or height. With "Keep aspect ratio" ticked, the other number follows automatically and is rounded to a whole pixel.
3. Or press 25%, 50%, 75% or 200% to scale from the original size in one click.
4. Pick a Format (JPG, PNG or WebP) and press "Resize & download". The file name gains the new size, for example holiday-1200x900.jpg, and the page reports the dimensions and the file size in KB.

How the resize happens

Your browser decodes the image, draws it onto a canvas of exactly the width and height you asked for, then saves that canvas as a new file. Smoothing is set to high quality, which blends neighbouring pixels when an image shrinks. JPG and WebP outputs are saved at quality 0.92, a high setting that keeps files noticeably smaller than the original without obvious artefacts. PNG is lossless, so the quality setting does not apply and its size depends on how detailed the picture is.

The aspect ratio is the original width divided by the original height. When you change the width, the height becomes width divided by that ratio. Example: a 4000 by 3000 photo has a ratio of 1.333. Setting the width to 1200 gives a height of 900. Pressing 25% gives 1000 by 750 directly.

Why a smaller image is a smaller file

An image's size on screen is its pixel count, and memory cost grows with the area, not the width. Halving both dimensions leaves a quarter of the pixels. A 4000 by 3000 photo has 12 million pixels, which is roughly 48 MB when decoded in memory, while a 1200 by 900 version has about 1.1 million. That is why scaling to 800 to 1200 px wide for web or email shrinks files dramatically. A rule of thumb for pages is to export at the largest size the image will actually be displayed, and at up to twice that for sharp results on high-density phone screens.

Choosing a format

• JPG: best for photographs. It has no transparency, so transparent areas are filled with white before saving.
• PNG: best for screenshots, logos and graphics with sharp edges or transparency. It can be large for photos.
• WebP: usually smaller than JPG at similar quality and supports transparency, but a few older programs cannot open it.

When you load a JPG, PNG or WebP, the Format menu switches to match it. Other types the browser can display, such as GIF or BMP, still load, but you will need to choose the output format yourself.

Common sizes in practice

The list above the FAQ gives the usual targets. Remember that "Keep aspect ratio" will not crop a photo into a different shape. To produce an exact 1200 by 630 preview from a 4:3 photo you would need to crop first. If you untick the lock and type both numbers, the picture is stretched or squashed to fit, which is rarely what you want for faces or text.

Tips and limits

• Shrink, do not enlarge, when you can. The 200% button doubles the dimensions, but no new detail is created; the result is just a blurrier large image.
• Resize from the original file, not from an already resized copy. Each JPG or WebP save loses a little information, and repeated saves add up.
• The output is a new file made from pixels only. Extra data stored in the original, such as camera details or location tags, is not copied over.
• Animated images are reduced to a single frame, because a canvas draws one picture.
• The limit is 100 megapixels for the result; larger requests are refused with a message. Very large photos may also be slow on older phones.
• Width and height must be whole positive numbers. Decimals are rounded.

Typical jobs

• Shrinking phone photos so they fit an email attachment limit or an upload form.
• Preparing images for a blog post or a shop listing that asks for a maximum width.
• Making a thumbnail version of a picture for a document.
• Enlarging a small icon slightly for a slide, accepting some softness.

More questions