Making Images Smaller and the Right Shape
Photos straight from a phone are several megabytes and far larger than any web page needs. That weight is the most common reason a site feels slow on mobile data, and it is the easiest thing to fix. Compressing an image before you upload it routinely cuts the file by most of its size with no difference you can see on a screen, which improves both how the page feels and how search engines score it.
Work in this order: resize to the dimensions you will actually display, then compress, then convert the format if you need to. Doing it the other way round means you compress pixels you are about to discard. Every tool here processes the file inside your browser, so the image is never uploaded anywhere, which matters when the photo is a document, an ID or something not yet published.