How to compress an image without uploading it

The quick way

Compressing an image takes a few seconds, and the file stays on your device the whole time:

1. Open Compress Image and drop one or more images on the page, or paste one from the clipboard.
2. Pick a preset. Balanced suits most photos, Strong squeezes harder, For a website saves WebP no wider than 1920 px, and For email saves JPG no wider than 1600 px.
3. Drag the before and after slider over detailed areas such as faces, hair and text to check the result.
4. Download each file, or everything as a ZIP.

Where file size comes from

Three things decide how big an image file is: how many pixels it has, which format stores them, and how hard the encoder is allowed to compress. A 12-megapixel phone photo holds twelve million pixels whatever its format, so shrinking it to the size it will actually be shown at is often the biggest single saving.

Format comes next. At similar visual quality, WebP is typically 25 to 35 percent smaller than JPEG, and AVIF is often around half the size. Screenshots and flat graphics behave differently: they compress best as PNG with a reduced palette, or as lossless WebP.

Resize first, then compress

If a photo will be shown 1200 pixels wide, a 4000-pixel original spends most of its bytes on detail nobody will see. Compress Image can limit the longest side, set a width or scale by percent under More options, and Resize Image gives more control, including fit, fill and pad modes. Downscaling usually saves more than lowering quality, and it hides compression artifacts instead of adding them.

Let the tool choose the settings

If you would rather not pick a quality number, Smart Optimizer encodes your image at several settings and keeps the smallest result whose structural similarity (SSIM) to the original stays above the level you choose. Format Shoot-out does the same across JPG, WebP and AVIF and keeps whichever format comes out smallest.

Both are measurements rather than guesses, but SSIM is still an approximation of human vision. Look at the result before you replace your originals.

Metadata is removed by default

Compress Image strips EXIF data from the output, which also removes GPS location, capture time and camera details. That saves a few kilobytes and protects your privacy. If you need the camera details in a compressed JPG, turn on Keep EXIF metadata under More options.

What compression cannot do

A few limits are worth knowing before you start:

• It cannot make a blurry or noisy photo look better. To an encoder, noise is detail, and detail costs bytes.
• Lossy compression cannot be undone. Keep your originals, because compressing an already compressed JPEG again saves little and adds artifacts.
• If a file cannot be made smaller, Compress Image returns the original unchanged and says so, rather than handing back a bigger file.
• Very large images, over roughly 100 megapixels, can exceed what a browser tab can safely hold, and phones reach their limits sooner.