Compress JPG

JPEG compression splits the picture into 8 × 8 pixel blocks and stores fine detail in each block more coarsely as the quality number drops. At 80 the loss is very hard to see in a normal photo at normal size, while the file shrinks a lot. Our 1200 × 800 test photo went from 224,092 to 132,872 bytes, 41% smaller. A 2400 × 1600 photo of 631,537 bytes came out at 234,132 bytes, partly because the default caps it at 1920 × 1280.

Guidelines that hold for most photos: 85–90 for images you may edit or print later, 75–80 for websites, email and upload forms, 60–70 when a strict size limit matters more than detail. Below about 60, block edges show in skies and around hair and text.

Every JPG has been through the encoder at least once. Running it through again at a similar quality saves little and costs a little detail, a loss known as generation loss. That is why the compressor compares sizes and hands back your original whenever its result would not be smaller. A phone photo saved at quality 95 or more has plenty of room; a picture downloaded from a website at quality 70 often has none.

When the quality slider alone is not enough, the pixel dimensions are the bigger lever. A 12-megapixel phone photo shown on a 1920-pixel screen is mostly invisible detail, and halving the width and height cuts the pixel count to a quarter. If you need a hard limit such as 200 KB, set it as the target size and the compressor lowers quality and size step by step until it fits.

By default the compressed file carries no EXIF data, which removes the camera model, capture date and GPS location. Turn on Preserve EXIF if you need them. The photo is drawn upright before encoding, so portrait shots from a phone stay portrait even in software that ignores the orientation tag.

The output format is preset to JPG, so a PNG or WebP you add here is converted to JPG too. JPG has no transparency: transparent areas are filled with white. For the same 1200 × 800 photo, WebP at quality 80 came to 93,112 bytes, about 30% less than the JPG; choose it in the format menu if the place you are uploading to accepts WebP.

The compressor runs on your device. Each JPG is decoded, scaled and re-encoded in the browser tab, and nothing is sent to a server, which matters for ID photos, scanned documents and pictures of family. Up to 10 files fit in one batch at 50 MB each, and Download all saves them as a ZIP. For a folder of 50, use the bulk compressor.