Resize Image

Two ways to say how big

Pixels mode is for when something else has decided the number for you: a portal that insists on 1200 pixels wide, a template that expects a 600 pixel banner, a listing that rejects anything over 2000. Type into the width box and the height follows automatically while the aspect ratio lock is ticked, and typing into height works the same way in reverse. Percent mode is for when you just want it smaller by feel. Enter 50 and both dimensions halve; enter 25 and a typical phone photo drops to a quarter of its width and height, which is a sixteenth of the pixels. Percent mode always scales both sides together, so the picture cannot be distorted there. Untick the lock in pixels mode only when you deliberately want to stretch an image to fixed dimensions.

What happens when you press the button

A blank canvas is created at exactly the target width and height, with image smoothing turned on at its highest quality setting, and your picture is drawn onto it in one step. If the chosen output format is JPEG, the canvas is painted white first, because JPEG cannot store transparency and an unpainted area would otherwise come out black. The canvas is then encoded to the format you picked, with the quality slider passed through for JPEG and WebP and ignored for PNG, which is lossless. The finished file downloads immediately with a name that records the dimensions, and a preview appears below the controls with the real file size in kilobytes so you can see whether you have hit the target.

A worked example

Take a 4032 x 3024 photo straight off a phone, about 3.6 MB. Switch to Percent and enter 25, and you get 1008 x 756. Or stay in Pixels, type 1200 into width, and with the lock on the height fills in as 900 by itself. Choose JPEG, leave quality at 0.92, and press the button: the preview reports something in the region of 200 KB, and the file arrives as resized-1200x900.jpg. Drop the quality to 0.70 and repeat, and the same dimensions come back at roughly half the size with a little softening in areas of fine detail.

Everyday reasons to resize

• A government or insurance portal that refuses anything over a stated file size or pixel width.
• A LinkedIn or Seek profile photo that needs to be square and modest in size.
• Product photos for an eBay or Etsy listing, where oversized files slow the page down for buyers.
• Images for a WordPress or Shopify post, cut down before upload so the media library stays tidy.
• Photos for a school or club newsletter that has to stay small enough to email.
• A batch of holiday photos scaled down before sending them to relatives over a slow connection.

If the requirement is phrased as a file size rather than a width, our guide to compressing photos for online forms explains how the two interact and which upload limits catch people out.

Limits and gotchas

Only PNG, JPEG and WebP inputs are accepted. There is no HEIC support here, so iPhone files saved in their original format need converting first. One image at a time, with no batch or folder mode. Upscaling is allowed but cannot invent detail that was never captured: the browser interpolates between existing pixels, so a 400 pixel image blown up to 1600 looks soft and slightly plastic. The tool does not crop or pad, so it cannot force a landscape photo into a square frame without stretching it. Exported files carry no camera metadata, since the canvas only holds pixels, which is handy for privacy but means copyright fields and capture dates are lost. Colour profiles are handled by the browser during decoding, so a photo in a wide gamut profile may shift slightly towards standard colours. Everything happens in your browser and nothing is uploaded to a server, so very large images depend on your own device's memory, and a 50 megapixel file on an old phone may simply fail. Resizing costs nothing, and a brief rewarded ad stands in whenever your credit has run out.

Format and quality, briefly

PNG is lossless and keeps transparency, which makes it right for logos, screenshots and anything with flat colour or sharp text, but it produces large files for photographs. JPEG is the safe default for photographs and is accepted everywhere, at the cost of throwing away transparency. WebP usually gives the smallest file at a comparable quality and is supported by every current browser, though some older desktop software and a few upload forms still reject it. The quality slider runs from 0.10 to 1.00 and sits at 0.92, which is close to visually lossless for most photos. Below about 0.60 you will start to see blocking around edges and in skies.

Related tools

To change the shape of the frame rather than its scale, use Crop Image. When the requirement is an exact file size, Compress Image to KB searches for the quality setting that lands on your target. To swap formats without changing dimensions, use the Image Converter, or HEIC to JPG for iPhone photos that will not open. For sideways scans there is Rotate & Flip Image, and for fixed social dimensions see Instagram Story Resize and YouTube Thumbnail Resize. To combine several resized photos into one document, try Images to PDF, and to strip location data from the originals use EXIF Viewer & Remover.

FAQ

Will transparency survive the resize?

Only if you export as PNG or WebP. Choosing JPEG paints the canvas white first, so transparent areas turn white rather than black, which is the usual reason a logo suddenly gains a background.

Is it worth making an image bigger?

Rarely. The browser can only interpolate between the pixels that already exist, so enlarging beyond about 150% of the original looks soft. Start from the largest version of the file you have wherever possible.

What does the quality slider change?

It sets the compression level for JPEG and WebP output only. Lower settings make smaller files with more visible artefacts around edges. PNG ignores it completely because PNG compression discards nothing.

Why is the height changing when I type a width?

The aspect ratio lock is on by default, so the second dimension is recalculated from the original proportions to stop the picture being stretched. Untick it if you genuinely need non proportional dimensions.

What is the downloaded file called?

It is named after the size you produced, for example resized-1200x900.jpg, with the extension matching the format you selected.