Is jpg the best format?

It seems like jpg is mostly used with pictures, why is that?

Dynentan said:

It seems like jpg is mostly used with pictures, why is that?

JPG is a lossy format that's good for photos and is used by most cameras. Its compression ratio can be adjusted for the best compromise between quality and file size. It's not so good for diagrams and screenshots of your PC where there is text that needs to be clean and crisp, PNG is more often used for this. The PNG format is lossless but can produce quite small files if there are large areas all the same colour, as is often the case in a screenshot.

More comparison of image formats here:

Image File Formats: When to Use Each File Type

I don't really see that much of a difference between jpg and png.

Dynentan said:

I don't really see that much of a difference between jpg and png.

The difference becomes apparent if you enlarge the image, you can see the jpeg compression artefacts then, such as the grey speckled dots around the text in the lower image here.

Okay, i see it clearly.

Good lossy format with common support.

Browsers are trying to phase it out with WebP which is compressed better but less supported.

JPG at 92% compression will be be suitable for most general everyday uses. PNGs are much larger (10x at least), but have better image quality and color-depth. WebP images can be a security risk on Windows 7, unless you have software which has patched the .DLL for a major recent security hole.