Image Format Converter

How Image Format Converter Works

This tool converts an image between PNG, JPG, and WebP entirely inside your browser, using the HTML canvas element to decode and re-encode the file -- nothing is ever uploaded to a server, so the image never leaves your device.

Formula & Method

The selected file is drawn onto an off-screen canvas at its original pixel dimensions, then the canvas is exported to the target format using the browser's own built-in image encoder at its default quality setting. PNG is a lossless format, so converting to PNG never discards image detail (though it can still change file size, sometimes substantially, since PNG and JPEG/WebP compress very differently). JPG and WebP are lossy formats that apply compression, which is why converting a photo to one of them usually shrinks the file. The reported "New Size" and the size delta compare the freshly encoded output directly against your original file's size.

Worked Example

Because the exact output size depends on the browser's built-in encoder and on the specific image's content (a simple flat-color graphic and a detailed photo compress very differently), this tool doesn't predict an exact number in advance -- but as a general pattern, converting a large photographic JPG or PNG to WebP typically produces the smallest file for the same visual quality, converting a photo from PNG to JPG usually shrinks it noticeably (PNG doesn't compress photographic detail as efficiently as JPEG's lossy compression), and converting a JPG to PNG often increases file size since PNG has to losslessly store detail that JPEG had already compressed away.

Frequently Asked Questions

Is any of my image data uploaded anywhere?

No -- the entire conversion happens using your browser's built-in canvas and image-encoding APIs, on your own device. The image file is never sent over the network.

Will converting to JPG or WebP lose image quality?

Yes, to some degree -- JPG and WebP are lossy formats, so converting a PNG (or another lossy file) to one of them applies compression that discards some detail, using the browser's default quality setting. PNG conversions are lossless and won't discard detail, though the resulting file size can still differ a lot from the original.

Why did converting to PNG make my file bigger, not smaller?

PNG is a lossless format, so it has to store every pixel's detail exactly rather than approximating it the way JPEG or WebP do. Converting a photographic JPG to PNG often produces a larger file, because PNG can't take advantage of the same lossy compression tricks that made the original JPG small.

Does this tool resize or crop my image?

No -- the image is redrawn onto the canvas at its original width and height and only its file format (and, for lossy formats, its compression) changes. Dimensions stay exactly the same, as shown in the result panel.