Step by step with the Image Compressor
- Add the images to compress: drag them in, choose them, or paste one.
- Leave Best for each file to keep photos as JPG or WebP and turn PNGs into palette PNGs, or pick one output format for all of them.
- Choose By quality and set the slider, or choose By target size and enter the size you need in KB, such as 100 for a form upload.
- Optionally enter a maximum width: larger images are scaled down first, which saves far more than quality alone.
- Select Compress, select a file to compare it before and after, and download the results one by one or as a ZIP.
A real example
Three files compressed with Best for each file at 75 % quality:
| File | What happens |
|---|---|
| IMG_2041.jpg, 4032 × 3024 | Re-encoded as JPG at 75 %. Typical phone photos lose most of their size with no visible change on screen. |
| screenshot.png, 1920 × 1080 | Reduced to a palette PNG. Screenshots of documents and interfaces often shrink by half or more. |
| already-small.jpg | Re-encoding made it larger, so the original is kept and marked as already well compressed. |
Each result reads, for example, Original: 2.40 MB · Compressed: 680.0 KB · Saved: 72.3% · JPG, and after a batch the status line totals the saving across every file.
What happens to your image
By quality re-encodes each image at the quality you set. By target size searches for the answer instead: the image is encoded at a middle quality, then at the middle of whichever half the result points to, and so on, seven times at most, keeping the highest quality whose file fits. If even the lowest quality is too large, the image is scaled down by the amount the sizes suggest, and the search runs again.
With Best for each file, photographs stay JPG (or WebP), and PNG and GIF files are reduced to a palette of at most 256 colours. The palette is built by median cut, which splits the image's colours into groups until there are 256, and pixels are then matched to the nearest palette colour with error diffusion so that gradients do not turn into bands. An image that already has 256 colours or fewer keeps every colour exactly. The palette PNG is written with the smallest bit depth its colours allow: 1, 2, 4 or 8 bits per pixel.
A maximum width scales larger images down before compressing, which usually saves more than any quality setting: a phone photo 4000 pixels wide has more than four times as many pixels as the same photo at 1920. When re-encoding would produce a larger file, the original is kept and the result says so.
When the Image Compressor helps
- Getting a photo or a scanned signature under the size limit of an online application form, such as 50 KB or 200 KB.
- Making product photos load faster on a website without a visible loss.
- Reducing screenshots and diagrams saved as PNG, which often shrink by half as palette PNGs.
- Fitting a set of holiday photos into an email attachment limit.
If the result is not what you expected
- Already well compressed: the original is kept
- Re-encoding produced a larger file than the one you started with, which happens with files that are already optimised. The original is offered instead. To go smaller, lower the quality, set a target size or enter a maximum width.
- The target size could not be reached
- Even the lowest quality at full size was larger than the target, so the image was also scaled down as far as it sensibly could be. Set a maximum width yourself, choose WebP instead of JPG, or allow a slightly larger target.
- A compressed PNG shows banding in smooth gradients
- A palette PNG has at most 256 colours, and smooth gradients in photographs need more than that. Save photographs as JPG or WebP instead, which handle gradients far better at a smaller size.
Questions about the Image Compressor
How does compressing to a target size work?
The compressor encodes the image repeatedly, halving the range of qualities each time, and keeps the highest quality that fits under your target. For PNG it reduces the number of colours instead. Only when the lowest quality is still too large does it scale the image down, and the result says when it did.
What quality should I choose?
For photographs, 75 to 85 percent is usually indistinguishable from the original on screen and far smaller. Go higher for images that will be edited again or printed large, and lower only for thumbnails. Screenshots and graphics with text are better as palette PNG than as JPG.
Why did my PNG become so much smaller?
It was reduced to a palette of at most 256 colours and written as an indexed PNG. Screenshots, icons and diagrams rarely use more colours than that, so the change is invisible; an image that has 256 colours or fewer to begin with is converted exactly, without any loss.
Is my photo uploaded to compress it?
No. Compression runs in your browser, so the photo never leaves your device, which matters for scans of documents and signatures.