How to make a photo smaller without uploading it, and what size to pick

Drop the photos on SHRINK, choose a longest side (1920 pixels for anything seen on a screen, 1280 for a chat or a listing) and a quality (82% for JPEG), and get them back one by one or as a zip. A phone photo typically comes out at a third to a tenth of its size and looks the same. The browser does the decoding and the encoding itself, so the result carries no location, camera or time, and nothing is uploaded. It opens an iPhone's HEIC and writes JPEG, WebP or PNG.

What makes the file big

Two things: the number of pixels and how loosely they are compressed. A modern phone takes a picture four thousand pixels across. A laptop screen is about two thousand; a phone screen, held upright, about a thousand. So the picture has four to sixteen times the pixels any screen will show, and every pixel is bytes. The second thing is that the phone saves the picture at a high quality setting so the shop can sell the camera, and a JPEG at that setting is two or three times the size of one nobody could tell apart from it.

Shrinking a photo is the two settings in turn: take the pixels down to what will be seen, and encode them at the quality where the loss is invisible. Both happen in the tab.

What size to pick

SHRINK never enlarges. A picture already smaller than the number you choose stays as it is, because adding pixels only blurs it.

What quality to pick

For JPEG, 82%. That is the point where a photograph has lost almost nothing you can see and most of its bytes; the curve is steep there. Below 60% the loss shows on skies, skin and gradients as blocks and banding. Above 90% the file doubles for a difference nobody can find. For WebP the same numbers hold and the file is smaller again, about a quarter less than JPEG at the same look, and every current browser shows it; it is the right choice for a website and the wrong one for a form that says JPEG.

PNG has no quality setting. It is exact, every pixel as it was, which makes it right for a screenshot with text on it (JPEG smears text) and wrong for a photograph, where it is three to five times the size of a JPEG that looks identical.

An iPhone's HEIC

iPhones save photographs as HEIC by default, and most software, Windows included, cannot open one. SHRINK opens it (a decoder is fetched from this site the first time and kept) and writes a JPEG, so the picture that would not open becomes one that opens everywhere, smaller, in the same step. How to open a HEIC file explains the format.

What happens to the location and the camera

A photograph from a phone carries where it was taken to a few metres, when, and which phone. SHRINK draws the picture onto a canvas and encodes a new file from the pixels, and a canvas has no location, camera, serial number or time to write, so the result has none. That is the same thing CLOAK does on purpose, here as a side effect of the resize. Does a photo show where it was taken? says what is in the original.

A photo that came in sideways comes out upright. The orientation flag a phone writes is applied before the pixels are drawn, so the picture you see is the picture you get, and no viewer has to be trusted to read the flag.

A hundred at once

Drop the folder. Every picture is shrunk with the same settings, in the tab, and the results come back as a zip or into the folder you have chosen for the site. There is no queue and no limit except the machine's memory; a few hundred phone photos is an ordinary afternoon's batch.

What this does not do

• Make a small picture better. It can only take pixels away.
• Keep an animation. An animated GIF or WebP is flattened to its first frame.
• Shrink a PDF. The pictures inside a PDF are a different job.
• Crop or straighten. PHOTO does that, and OBSCURA Photo Editor does everything else.