Why PNG screenshots are so heavy
PNG stores every pixel exactly as it is. For a logo or a diagram with twelve flat colours that is brilliantly efficient. For a screenshot of a busy dashboard, or a photograph someone saved as PNG by accident, it is the worst possible choice: there is no repetition to squeeze, so the file balloons into several megabytes of an image nobody will inspect pixel by pixel.
JPG makes the opposite trade. It throws away detail the eye does not register and stores the rest compactly. That is why the same screenshot lands so much smaller, and why it finally fits an email attachment limit, a job application upload, or a form that quietly refuses anything over two megabytes.
Choosing a quality level
- 85 percent, the default. The right answer nearly always. Big saving, no visible difference.
- 95 to 100 percent. For images you will crop or edit again, where you want the compression to stay well out of the way.
- 60 to 70 percent. When a hard upload limit is the only thing that matters. Fine details start to soften here.
- Below 60 percent. Visible blocking around text and sharp edges. Worth it only under real pressure.
One caveat worth knowing: text and thin lines are exactly what JPG handles worst. If your PNG is a screenshot of a document, converting the pages to a PDF keeps them sharp and is usually what the recipient wanted in the first place.