Resize images: exact pixels or percent, nothing uploaded

Compressing a photo keeps every pixel but throws away detail the eye barely notices, which is what a quality slider does. Resizing removes pixels outright: a 4000×3000 photo resized to 1200×900 has nine times fewer pixels to store, so the file shrinks dramatically even before any quality setting is touched. Most of the savings people are chasing when they say 'make this smaller' actually come from resizing, not from lowering quality.

This matters because the two dials solve different problems. If a form rejects your file for being too large in megabytes, resizing usually fixes it in one step. If the photo already looks fine on screen but you want a smaller archive, lowering quality first and resizing only if that is not enough keeps more detail.

A useful rule when you are not sure which one you need: resize first, look at the result, and only reach for quality afterward. A photo that is already the right pixel size rarely needs to go below quality 70 to hit a reasonable target, whereas a photo left at full camera resolution can need aggressive, visibly damaging quality settings to reach the same file size.

A longest-side preset is the fastest way to resize a mixed folder of portrait and landscape photos because the shorter side scales automatically. Custom pixels can instead set an exact width or height while keeping proportions, or unlock the ratio to force both dimensions. Forced dimensions do not crop or pad: if their shape differs from the source, the picture stretches. Enlargement is off by default because adding pixels cannot restore detail.

To see actual numbers rather than estimates, we ran this page on a 1600×1000 synthetic test pattern (gradient, color bars, thin lines, a circle and a label) made in the browser, not a photograph, saved as a 120,706-byte JPEG. We also ran a second test file, a 1254×1254 pixel-art PNG — again not a photograph.

All cases use the same steps: pick Custom pixels under photo size, enter the pixel values, toggle Keep proportions on or off, then press Apply to all. We only measured these two synthetic test files; results on real photographs were not measured. The runs were repeated and produced byte-identical output in the same browser; other browsers or encoders may differ.

Print and ID-photo requirements are usually given in centimetres or inches at a fixed resolution, almost always 300 dots per inch. The conversion is pixels = centimetres ÷ 2.54 × 300. A Korean resume or student-ID photo at 3×4 cm becomes 354×472 px, and a passport-style photo at 3.5×4.5 cm becomes 413×531 px; a US visa photo at 2×2 inches is 600×600 px. Screens need far fewer pixels than print: a photo shown at 10 cm on a laptop screen only needs about 380 px at typical screen density, which is why a resized, web-sized image still looks sharp on a monitor.

Add every photo you need to shrink in one go, dozens at a time. The same longest-side or percent setting applies to the whole batch, each file keeps its original name, and the results download individually or as a single ZIP so you are not clicking 'save' fifty times. Because resizing runs in your own browser, there is no queue, no daily cap and no account, and nothing about the photos themselves leaves your device.

Sellers on marketplaces and small online shops usually need every product photo at the same pixel size so listings look consistent, but shooting on a phone gives every photo a slightly different resolution depending on zoom and cropping. Setting one longest-side value and running the whole folder through it fixes that in one pass instead of eyeballing each photo individually. Most marketplace and social platforms cap uploads well below a modern phone photo's native size anyway, so resizing down to roughly 1600–2048 px before uploading avoids the platform doing its own, less predictable, resize on the way in.

Enlarging a small photo to a larger pixel size does not add detail; the encoder can only stretch and blur what is already there, so upscaling a thumbnail for print will always look soft. Forcing an odd-shaped source into a fixed width and height without cropping first distorts faces and objects, which is especially visible in ID photos. And resizing after compressing is backwards: shrink the pixel dimensions first, since a smaller image needs a smaller file regardless of quality, then apply quality or a target size only if you still need to go further.

Sending a resized photo through a chat app adds a second, invisible resize: Kakao, Messenger and similar apps re-compress images on send, so a file you already shrank carefully can lose more than expected. When quality matters, such as a document photo, send it as a file attachment rather than as a picture, or check the app's option to send the original size.

Windows Photos lets you right-click an image and choose Resize, but it works on one file at a time. On a Mac, Preview has Tools, Adjust Size, also one photo per pass. iPhone and Android have no built-in bulk resize at all. This page does the same pixel math as those tools but on as many photos as you have, on any device with a browser, without installing a codec, an app or an extension.