Resize an image without uploading it

Resize for Instagram, YouTube, LinkedIn, a blog or email. Resize for Instagram

Downsize changes the dimensions of a JPG, PNG or WEBP image using your browser's own image tools. The file is read from your device and worked on there — it is never sent to a server, and no copy of it exists anywhere but your own machine. Pick a width, or choose one of the common sizes listed further down. You can also compress it to a target file size, or convert between JPG, PNG and WEBP, and download the result.

How to resize an image

1. Drop an image onto the page, or choose a file from your device.
2. Pick a platform for a ready-made size, or enter the width you need. The height follows automatically unless you unlock the ratio.
3. Check the before and after figures — dimensions and file size update as you type.
4. Download the resized image.

Why resize in the browser

Most image tools work by uploading your file to a server, changing it there, and sending it back. That means a copy of your photo sits on hardware you do not control, for a length of time nobody tells you. Downsize does the work in the page itself, so there is no upload, no second copy, and nothing left behind to delete.

Skipping the upload also removes the waiting. There is no queue and no round trip, so a large photo is resized in well under a second and the preview keeps up while you are still adjusting the number. The only real limit is your own device.

There is also nothing to sign up for. No email, no free tier, no watermark on the way out, and no record that you were ever here. Open the page, do the one thing, close the tab.

JPG, PNG or WEBP, which to use

The format decides how much of the file size you can trade away and what you lose in return. Downsize always saves back to the format you opened, so this is a choice you make before you resize an image rather than after.

JPG

JPG is built for photographs. It throws away detail your eye is bad at noticing, which is why a twelve-megapixel photo can sit in a few hundred kilobytes and still look right. It is the wrong choice for screenshots, logos and anything with flat colour, because the same trick that flatters a sky leaves visible smears around hard edges. The mistake people make is saving text as JPG — the compression works in small square blocks, and a sharp letter edge inside one produces a grey halo that no amount of quality setting fully removes.

PNG

PNG keeps every pixel exactly as it was and supports transparency, which makes it the right answer for screenshots, diagrams, line art and anything that has to sit on a background. It is the wrong choice when the image is a photograph: with no repeating areas to compress, the file can be five or ten times the size of the equivalent JPG for no visible gain. The mistake people make is treating PNG as the high-quality option and using it for photos, then wondering why an image they resized is still enormous.

WEBP

WEBP does both jobs — lossy like JPG, lossless and transparent like PNG — and is usually smaller than either at the same quality, which is why it is a sensible default for anything going on the web. It is the wrong choice when the file has to leave the web: older versions of Office, Photoshop and plenty of print workflows still refuse to open it. The mistake people make is converting an archive to WEBP for the space saving and finding out later that the software they need cannot read a single one of them.

What happens when an image is resized

Making an image smaller is an averaging job. Several pixels from the original are combined into one, so the detail that was there is condensed rather than discarded, and the result stays sharp. Going the other way cannot work the same, because there is nothing to average — enlarging has to invent pixels between the ones that were recorded, and invented pixels are a guess. That is the real reason a photo you resize upwards looks soft while the same photo resized down looks fine.

How the shrinking is done matters as much as by how much. Ask a browser to draw a 4000-pixel-wide photo into a 400-pixel box in one step and it samples a fraction of the source pixels and ignores the rest, which turns fine detail into speckle and makes straight lines crawl. Halving repeatedly instead — 4000 to 2000 to 1000 to 500, then the last short step — means every original pixel contributes to the result. Downsize does it in steps for exactly this reason, and it is the clearest difference between it and a tool that hands the whole reduction to one draw call.

Getting the size right for each platform

Every platform crops, and each one crops differently. Matching the dimensions before you upload is the only way to decide what gets cut, rather than finding out afterwards.

Instagram accepts 1080 × 1080 square, 1080 × 1350 portrait and 1080 × 1920 for stories. Portrait is the tallest the feed will show, and anything taller is cropped to it. On a story, roughly the top and bottom sixth sits under the interface, so keep anything that has to be read away from both edges.

YouTube thumbnails are 1280 × 720, but they are almost never seen that large — in a sidebar or a phone list the same image is a couple of hundred pixels wide. Text that reads comfortably at full size often disappears there, which is the thing worth checking before you settle on one.

LinkedIn profile banners are 1584 × 396, and the profile photo overlaps the lower left corner on desktop. The mobile app crops the sides in further, so the usable area is a band across the middle and to the right of where the photo sits.

Facebook page covers are 820 × 312 on a desktop browser and are cropped to a squarer shape on a phone, taking slices off the left and right. Keeping the important part of the picture within the centre is the only version that survives both.

X shows attached images at 16:9 in the timeline, so 1600 × 900 fits without anything being cut. A taller image is not lost, but it is cropped to that shape until someone taps it, and a caption near the bottom is the usual casualty.

Common image sizes

These are the presets built into the tool, grouped by platform. Anything not listed can be typed in directly.

Questions

Are my images uploaded to a server?

No. Downsize reads the image directly in your browser and does all the work there. The file never leaves your device, and there is no server involved at any point.

What file types can I resize?

JPG, PNG and WEBP, and you can convert between them. By default the image you download is the same format as the one you opened; the Convert tab changes that if you want it to.

Is there a file size limit?

Files up to 30 MB are accepted. The limit is checked before the image is opened, so a file that is too large is rejected straight away rather than slowing the page down.

Will resizing reduce the quality?

Making an image smaller keeps it sharp, because the detail is being condensed rather than invented. Enlarging past the original dimensions is allowed but will look soft, since there is no extra detail to draw on.

Does it cost anything?

No. Downsize is free, has no account, and adds no watermark. There is no paid tier to upgrade to.

What happens to transparency when I convert to JPG?

JPG has no transparency, so the clear areas have to become a colour. Downsize checks whether the image actually has any transparent pixels, and only asks when it does. You pick the fill colour, because white is right for a logo on a white page and wrong for one on a coloured page.

Does Downsize work offline?

Once the page has loaded, yes. Nothing is fetched while you resize an image, so the connection can drop and the tool keeps working. Loading the page in the first place still needs a connection, because there is no installed copy of it on your device.

Why is my PNG bigger after resizing?

PNG stores every pixel exactly, and it compresses by finding repetition. A photograph saved as a PNG has very little repetition to find, so shrinking it removes pixels but can still leave a file larger than the JPG you started from. If the original was a JPG, the honest comparison is against another JPG.

Can I resize several images at once?

Not yet. Downsize handles one image at a time, and the resize is fast enough that repeating it for a handful of files is quicker than it sounds. Batch mode is a reasonable thing to want and it is not ruled out.