If your screenshots are intended for documents, don't change the format to JPEG. Depending on the document (e.g. a PDF file) that compression can happen at a la

If your screenshots are intended for documents, don't change the format to JPEG. Depending on the document (e.g. a PDF file) that compression can happen at a later stage. You can always compress a PNG into a JPEG (it's a lossy operation), but once it's done, you can't come back. I often see JPEG screenshots in student reports (but not only), and they look really bad, as most of the time those are plots, drawings, and present very visible JPEG artefacts (e.g. colored noise around lines and text).