Why does srcset matter?
The same image needs a very different pixel size on mobile versus desktop. Serving one large original means mobile users download a desktop-sized file and pages load slower, while serving only a small file makes it look blurry on large screens. Using srcset together with the sizes attribute lets the browser automatically pick the most appropriate image file for the current viewport and screen density.
Enter your original image width and the percentage of the viewport it occupies, and this calculator computes the ideal image width for every major breakpoint from mobile to large desktop, rounded to standard sizes. Copy the generated srcset and sizes code straight into your image tag.
Frequently Asked Questions
They let the browser pick the right image file for the current screen size, avoiding unnecessarily large downloads and speeding up page load.
Usually 3 to 5 sizes are enough. Splitting into too many variants adds extra server requests and maintenance overhead.