Every tool on this page decodes your image with the browser's own createImageBitmap and Canvas APIs, then re-encodes it with canvas.toBlob(). The practical consequence is that the file never crosses a network: there is no upload progress bar, no server-imposed size cap, and no copy of your photo sitting in someone else's object storage after you close the tab. The trade is that your device's memory becomes the limit instead. A decoded bitmap costs roughly width × height × 4 bytes regardless of how small the file on disk was, so a 48-megapixel phone photo occupies about 190 MB of RAM while it is being worked on — fine on a laptop, tight on an older phone with a dozen browser tabs open.
JPEG and WebP are lossy, and the loss is generational. Each save discards a little more detail, and the damage compounds: re-compressing an already-compressed JPEG five times produces visibly worse output than compressing the original once at the same final quality. Always start from the highest-quality source you have. PNG is different — it is lossless for the pixel data — but most tools advertised as "PNG compressors" work by quantising the palette down to 256 or fewer colours, which is lossy. That is usually invisible on screenshots and flat-colour logos and very visible on photographs and smooth gradients.
On format choice: WebP typically lands 25–35% below a visually equivalent JPEG and is supported by every browser still receiving security updates, which makes it the sensible default for the web. Keep PNG when you need real transparency or crisp edges on flat colour — UI screenshots, logos, line art. Keep JPEG when the file has to be opened by older desktop software or uploaded somewhere that rejects WebP. HEIC is Apple's capture format: excellent on the device that produced it, awkward almost everywhere else, which is the entire reason a converter exists.
One thing worth doing before you share any photo you did not take on a computer: strip the metadata. Phone cameras write EXIF tags that include GPS coordinates to several decimal places, the device model, and the exact capture timestamp. Large social platforms strip these on upload; email attachments, direct file transfers, forum uploads and a good number of CMSes do not.
Which compressor should you use?
Five of the tools below overlap. The difference is what they are allowed to change:
| Tool | Input | Output | Best for |
|---|---|---|---|
| Image Compressor | JPG, PNG, WebP, GIF, BMP | Auto-picks the smallest format | General use — start here if you are unsure |
| Compress JPG | JPEG only | JPEG at your quality setting | Keeping the format when something downstream requires JPEG |
| Compress PNG | PNG only | PNG, transparency preserved | Screenshots and logos that must stay PNG |
| Convert to WebP | JPG, PNG | WebP | A one-way move to the smallest modern format |
| Batch Image Resizer | Mixed | Resized + re-encoded | Bulk work where dimensions, not quality, are the problem |