Quick and free: Carbon: https://carbon.now.sh
Convenient: Codesnap (VS Code Extension): https://marketplace.visualstudio.com/items?itemName=adpyke.codesnap
Pretty and free: Ray.so: https://ray.so
Browser-y: HTML2canvas: https://html2canvas.hertzen.com/
Real product best-in-class: Snappify: https://snappify.com/