A freelance portfolio is a page of images and nothing else, which means its speed is almost entirely a function of image weight. Deliver a dozen full-resolution JPEGs and the page crawls on a phone, and the client who clicked your link is already deciding whether to wait. The other half of the problem is sharpness: over-compress and your best work looks soft, which is the worst possible result on a portfolio specifically meant to prove craft. The way through is dimensions first, quality second. Resize each image to the size it actually renders at, then compress to a moderate quality that keeps detail. Skwish does both in the browser with a live size readout and a batch mode for the whole set, so you can optimize a portfolio end to end in a few minutes and keep the originals safe on your own machine.