The fastest route from any picture to a favicon
Not every site has a designed logo, and not every icon job justifies opening a design tool. Personal blogs, side projects, internal dashboards and staging environments all benefit from a recognizable tab icon, and the raw material is often just a photo: your face, your dog, your product, a photographed sketch. This tool takes that JPG and does the mechanical work correctly, producing a genuine multi-resolution ICO instead of a single renamed image, so browsers get a pre-rendered 16 pixel version rather than downscaling a large photo badly on the fly. Drop the result into the web root as favicon.ico and the job is done. If you first want to crop or clean up the picture, JPG to PNG gives you a lossless working copy, and JPG to WebP covers the site's other image needs.
Photos and logos want different treatment
A photographic icon and a logo icon fail in opposite ways, and knowing which you have saves a round trip. Photos fail by detail: a wide shot becomes unreadable mush at 16 pixels, so crop hard until the subject fills the frame. Logos fail by background: JPG stores no alpha channel, so a logo saved as JPG carries its white rectangle into the icon, which looks pasted-on against dark browser themes. In that case the fix is not this converter but a better source; find or export the logo as a PNG with real transparency and run it through PNG to ICO instead, and the icon's corners will disappear into any background. To see what is actually stored inside an existing favicon before replacing it, ICO to PNG pulls out the largest image for inspection.
Common questions
What does the icon look like when the JPG is not square?+−
The image is centered on a square canvas rather than stretched, so nothing is distorted. Because JPG has no transparency, the picture itself keeps its full rectangular look inside that square. For a favicon this is usually fine, but if you want the padding around a non-square image to be invisible, crop the JPG to a square before converting.
Why might a PNG be a better starting point?+−
Transparency. A logo-style icon usually wants transparent corners so it sits cleanly on any tab or taskbar background, and JPG cannot store transparency, so a JPG-sourced icon always fills its whole square. If you have the same artwork as a PNG with a transparent background, convert that instead via the PNG to ICO tool; the result will look more like a native icon.
Will a photograph work as a favicon?+−
Yes, and it is a popular shortcut for personal sites and blogs: a headshot or a distinctive object shot reads surprisingly well in a browser tab. The practical advice is to crop tightly around the subject before converting, because at 16 pixels anything in the frame besides the subject becomes indistinct noise. Strong color contrast against typical tab backgrounds helps too.
Which sizes end up inside the .ico?+−
The standard set: 16, 32, 48, 64, 128 and 256 pixels, each stored PNG-compressed inside the container so browsers and Windows can pick the size that fits the context. Sizes larger than your source image are skipped rather than upscaled, since inventing pixels would only blur the icon. A source of at least 256 pixels on its short side fills out every slot.