MockShot

MockShot is described on its page as a browser-based device mockup and screenshot generator for app makers, designers and small product teams. Users start with a screenshot, place it inside a device frame (phones, tablets, laptops, desktops, displays, watches, smart home), then build a composition with canvas dimensions, backgrounds, headlines and layers. Imports support PNG, JPG and WebP up to 20 MB; fitting options include Cover, Contain and Stretch. Exports are offered as PNG, JPG, WebP or SVG. The page notes SVG export embeds a rendered image rather than editable vectors, and JPG flattens transparency onto white. Local editing and rendering are stated to happen in the browser.