How to resize images without stretching, cropping or blurring them

Resizing looks like the simplest thing an image tool does, and it is the one people get wrong most often. The photo comes back squashed, or a head is cropped out of frame, or it looks soft on a retina screen. Almost always the cause is the same: the source and the target have different aspect ratios, and nobody decided what should happen about that.

Pixels, aspect ratio and the lock

The aspect ratio is simply width divided by height. A 4000 × 3000 photo is 4:3. If you force it into a 1000 × 1000 square by changing both numbers, every circle in it becomes an oval. That is what people mean when they say an image looks "stretched".

The link button between width and height in the Image Resizer prevents this. With the ratio locked, you type one number and the other follows. There is a detail worth knowing: with the lock on, only the side you typed is stored, and the other is worked out per image when the resize runs. That matters for batches — it means each photo keeps its own proportions instead of every image being forced into the shape of the first one.

The three resize modes

1. 1ExactYou type the width and height you want. The right choice when something downstream demands a specific size: an avatar, a banner slot, a print size.
2. 2PercentScale everything by the same factor. Good for "make this batch half the size" when the images are not all the same dimensions to begin with.
3. 3Max boxSet a ceiling rather than a target. Images larger than the box are scaled down to fit; images already smaller are left completely untouched. This is the mode you want for a website.

Fit modes: what happens to the leftover space

When you ask for an exact size and the ratios do not match, something has to give. The fit mode is where you say what.

In practice: cover for thumbnails, hero images and anything where filling the frame matters more than the edges. Contain for product shots and logos, where cropping would clip the subject — set the padding colour to match the page it will sit on, or make it transparent and export as PNG or WebP. Inside when you just want a size cap. Fill essentially never.

If cover crops the wrong part — it centres by default — resize with contain and then use the Image Cropper, where you choose the framing yourself and can lock the ratio while you drag.

Why upscaling doesn't work

Enlarging an image cannot add detail that was never captured. All any upscaler can do is guess at the pixels between the pixels you have, which produces something bigger but softer, in a much larger file. The "enhance" button in films is not real.

Leave Don't upscale turned on unless you specifically need a larger canvas — for example, padding a small logo out to an exact 512 × 512 icon size, where the extra area is background rather than invented image.

Downscaling, by contrast, is genuinely lossless-looking when done properly. ImageDoctor halves the image repeatedly rather than jumping to the target in one draw, so each output pixel averages more of the source. That is why text and hard edges stay clean instead of developing the jagged, sparkly look you get from a naive single-step resize.

What size should things actually be?

• Website content images: the widest they will ever be displayed, doubled for high-density screens. For most layouts 1600px wide is plenty.
• Full-width hero images: 2000–2400px wide. Beyond that you are paying for pixels nobody sees.
• Thumbnails: 400–600px on the long edge, cover fit.
• Avatars and profile pictures: 512 × 512, square, cover fit.
• Email attachments: 1600px on the long edge is more than enough for anyone to view or print at A4.
• Print: work backwards from the paper. 300 DPI × 8 inches = 2400px.

For social platforms, do not try to remember the numbers — they change. The Social Media Image Resizer carries the current post, cover, story and profile sizes for Instagram, YouTube, LinkedIn, X, TikTok and the rest, and produces all the variants you need from one source image.

Resizing a folder of images

Add them all to the resizer at once and one setting applies to the whole queue. Use Max box rather than Exact so that portrait and landscape shots both come out sensibly, and the aspect ratio of each is preserved.

If the same batch also needs compressing, converting or watermarking, do it in one pass with Batch Image Tools instead of running the set through four separate tools. Every step happens on one decode, which is faster and avoids re-compressing an already compressed result.

Sizes you use often can be saved as presets, so "1600 × 900" becomes one click next time rather than two fields to retype.