Which format should you pick?
WebP is the default here because it is the best general-purpose choice on the web today: for the same visual quality it is typically 25–35 percent smaller than JPG, it supports transparency like PNG, and every current browser reads it. Use it for anything that will be displayed on a website.
JPG remains the safest format for photographs you need to hand to someone else — print shops, older desktop software, and some marketplace upload forms still reject WebP. JPG has no transparency, so when you convert a transparent PNG to JPG this tool fills the background with white rather than producing black fringing.
PNG is lossless. It is the right pick for screenshots, logos, line art, and anything with sharp edges or flat colour, and the wrong pick for photographs, where it produces files several times larger than JPG for no visible gain. Because PNG is lossless, the quality slider is disabled when you select it.
How the quality slider behaves
The slider maps to the encoder's quality parameter. Between 100 and roughly 85 percent you are mostly paying for bytes no one can see. Between 85 and 70 percent most photographs stay clean while the file often halves. Below about 60 percent you start to see blocking in skies and gradients and halos around text. The 82 percent default is a deliberate compromise tuned for photographs destined for the web; drop it further for background images, raise it for product shots.
Re-encoding is lossy in one direction only. Converting a JPG to WebP at 90 percent will not restore detail the original JPG already discarded, and converting back and forth repeatedly degrades the image a little each time. Always start from the highest-quality original you have.
Why capping the width matters more than the format
The single biggest cause of bloated pages is a 4000-pixel-wide camera file displayed in a 800-pixel-wide slot. The browser downloads every one of those pixels and then throws most of them away. Setting a max width of 1600 for hero images, 1200 for in-article images, and 600 for thumbnails usually saves more bandwidth than any format change. This tool keeps the aspect ratio automatically and never upscales a small image.
Privacy and limits
The conversion uses your browser's own canvas and image decoders. The file is never transmitted, which means it also works offline once the page has loaded, and it means very large images are limited by your device's memory rather than by an upload cap. Animated GIFs are flattened to their first frame — this is a still image converter, not an animation encoder. Camera RAW files are not supported because browsers cannot decode them.
Looking for video and audio instead? Start from the tool index or read the guides.