Every one-click reverse image search extension works the same way, and it is not the way you'd guess. It doesn't upload anything. It builds a URL:

const ENGINES = {

google: (u: string) => `https://lens.google.com/uploadbyurl?url=${encodeURIComponent(u)}`,

bing: (u: string) => `https://www.bing.com/images/searchbyimage?cbir=sbi&imgurl=${encodeURIComponent(u)}`,

yandex: (u: string) => `https://yandex.com/images/search?rpt=imageview&url=${encodeURIComponent(u)}`,