Compress photos

What this does

Compress photos on the device you are using, without sending them anywhere. One photo opens large, with a split before-and-after that re-encodes itself as you change the recipe. A folder of four thousand opens as a contact sheet, with every photo a bar on the skyline above it, so you can see how many are too big before anything runs.

Either way there is one recipe and one receipt. You declare the rule once; every file meets it in turn and gets a row: what it weighed going in, what it weighs coming out, the setting that won and — where nothing was written — the reason in words. At the end there is a single line of arithmetic, and a file or a ZIP shaped like the folder you started with.

Setting the rule

• Quality is the setting most people mean by compression. It rewrites the same pixels more cheaply, and the three positions here are printed with the numbers the encoder actually receives.
• Size per file has three modes. A ceiling keeps every file under a size at the batch quality, searching down only the files that are over it. A target does the same and, when quality 40 is still too big, steps the pixels down until the file fits — this is what forms that say "under 50 KB" need. A range adds a minimum, reached with a higher quality and never with padding.
• Drag the line on the skyline to set the size and watch how many photos sit above it. It snaps to the sizes forms ask for: 10, 20, 30, 50, 100, 200, 300 and 500 KB, 1 and 2 MB.
• The long edge cap is the largest saving available on camera files and the only part of the rule that cannot be undone from the output, so it is off until you turn it on.
• Capture information — the date, the camera, sometimes the place — is kept by default here. What removing it would have saved is reported separately, so that choice can be made on a number.
• Two skip rules keep the total honest. Files under the floor are left alone unless the size rule needs them, and a re-encode that came out larger is thrown away with the original kept in its place.

What it will open

JPEG, PNG and WebP are read and written; GIF, BMP and AVIF are converted when the recipe names JPEG or WebP as the output. HEIC (the iPhone’s format) opens only where the browser decodes it itself, which today means Safari, and is written as JPEG; anywhere else each HEIC is left alone with the reason on its row. TIFF is not opened yet. Every file is identified from its leading bytes rather than its extension.

Anything else in a folder is counted and left alone: video, audio, sidecar files, RAW from any camera, and the half of a Live Photo that is a movie. Those are reported as unsupported rather than as failures, which matters in a report somebody is meant to trust before they delete anything.

Two kinds of file are skipped on purpose even though they could be opened. A CMYK JPEG would come back with its colours shifted, and a photo beyond what this browser can decode safely is skipped with its dimensions on the row instead of taking the job down with it.

Questions

How many photos can go in one job?

One, or up to five thousand files or twenty gigabytes, whichever a folder reaches first. One photo opens a large before-and-after; a set opens the contact sheet. The ceiling is shown before a folder is read, and a folder past it is cut there with the rest left untouched.

What happens to the originals?

Nothing. Every file is opened for reading, and the results are a download you save: one file for one photo, a ZIP for a set. No original is modified, renamed or deleted by this site.

Can I compress a photo to an exact size in KB?

Yes. Set Size per file to Target and type the limit (1 KB = 1,024 bytes): each photo gets the highest quality that fits, and when quality 40 is still too big its pixels step down until it fits. Range adds a minimum for forms that reject files that are too small. The dedicated pages for 20, 50, 100 and 200 KB start with those numbers set.

Why do some files come back unchanged?

Because re-encoding them would have made them bigger, or they were under the skip floor, or they are a CMYK JPEG whose colours would shift. Each kept file says which on its row, and the original goes into the ZIP in its place.

Can I close the tab?

The record of which files finished is kept in this browser after every file, but the compressed copies live in the tab until you save them. Closing the tab mid-run asks first. In Chrome and Edge, choose Save into a file as photos finish and every copy is on disk the moment it is ready; elsewhere, Save what's finished writes a part ZIP. When you come back and choose the same folder, finished files are recognised, and you choose whether to re-run them or skip them.

Is anything uploaded?

No. Photos are decoded and encoded by your browser in this tab, and the site has no address that could receive one. You can check: open your browser's network panel and run a job.