Image tool
Image Compressor
Compress images by quality or dimensions, process a batch, or search for the best quality that still fits an exact file-size cap.
Compress images
Up to 20 files · one at a time
PNG has no quality dial, so exact-size mode shrinks its dimensions. JPEG fills transparent areas with white. An image that is already small enough is returned unchanged.
Settings changed — compress again to apply them.
Images
Nothing queued yet
Your images will appear here.
Add a few files to compare the before and after.Files are processed sequentially to keep memory use predictable.
How it works
Add up to 20 JPEG, PNG or WebP images. Review the list and remove anything you do not want to process.
Choose quality mode or an exact target size, and optionally resize the output. Images are processed one at a time in your browser.
Check the before-and-after size and the preview, then adjust the settings if the result is not what you need.
Download each compressed image separately or take the whole batch as a ZIP.
Frequently asked questions
Which image formats can I compress?
JPEG, PNG and WebP input are supported, with JPEG, PNG and WebP output. AVIF and HEIC files are not supported by this version. JPEG has no transparency, so transparent areas become white; choose PNG or WebP when you need to keep transparency.
Does exact-size mode guarantee that byte size?
No. The target is a cap, not a guaranteed exact byte count. The compressor searches for settings that get under the target and may resize or re-encode the image. Some images cannot reach a very small target without unacceptable quality loss, so check the preview before downloading.
Are my images uploaded?
No. The images are decoded and compressed in your browser. Ontool does not receive the files, and there is no account or server-side gallery. The trade-off is that very large batches depend on your device’s memory.
What are the batch limits?
Up to 20 images per batch, with each image limited to about 60 megapixels. Exact-size targets must be between 1 KB and 50 MB, and a ZIP download is capped at 512 MB.
Why did my PNG get larger or ignore the quality setting?
PNG is a lossless format, so the quality slider does not work the same way as it does for JPEG or WebP. Re-encoding or resizing a PNG can make it larger. For a smaller photographic image, JPEG or WebP is usually the better output choice.
Can I resize while compressing?
Yes. You can set output dimensions as part of the compression job. Resizing changes the pixel dimensions, while the quality or target-size setting controls the encoded file size. Enlarging cannot add detail that was not in the original.