Resize image

Why resize images?

Right-sized images load faster and stop your pages shipping pixels no screen will ever show. OptImg resizes with a high-quality resampling filter and re-encodes in the same format, entirely on your device: no upload, no queue, and files as large as it can handle.

Frequently asked questions

Are my images uploaded to a server?

It runs at native speed entirely in your browser: nothing is uploaded, your image never leaves your device, and there are no size or file-count limits.

Does resizing keep the aspect ratio?

Yes by default: change the width and the height follows (and vice versa). You can unlock it to set an exact width and height independently.

Will it enlarge a small image?

Only if you ask. “Do not enlarge if smaller” is on by default, so a target larger than the original leaves the image untouched instead of upscaling it blurry.

What pixel size should I use for the web?

Match the space the image will actually occupy, then allow for high-density screens. A full-width hero on a desktop layout is usually well served by 1600–2000 pixels wide; an in-article image by 800–1200; a thumbnail or avatar by 200–400. Anything beyond about twice the displayed size is weight nobody will ever see. If you are unsure, work back from the largest width the image can reach in your layout and double it.

Why did my file get bigger after resizing?

Almost always because the format is lossless and the source was lossy. Re-saving a JPG as PNG at a smaller size can still produce a larger file, because PNG stores every pixel exactly, including the compression noise baked into the JPG. Keep the original format, or convert to WebP, and the size will fall with the dimensions as you expect.

Does resizing reduce quality?

Making an image smaller is generally safe: detail is averaged down rather than invented, and the result usually looks cleaner than the original viewed at that size. What does cost a little quality is the re-encode that follows, since a lossy format has to be written out again. Going the other way is the lossy direction — enlarging cannot recover detail that was never captured, which is why the guard against accidental upscaling is on by default. When you genuinely need a bigger image, the Upscale tool reconstructs detail rather than simply stretching pixels.

Can I set a width and height that don't match the original ratio?

Yes. Unlock the aspect ratio and both fields become independent, which will stretch or squash the image to fit exactly the box you asked for. That is occasionally what you want for a texture or a background, but for photographs it usually looks wrong, and cropping to the target ratio first gives a better result.

Does it resize animated GIFs?

Yes. Every frame is resized identically and the frame delays and loop setting are preserved, so the animation plays exactly as before at the new size.