Describe how wide an image shows at each breakpoint and get the correct sizes attribute, the widths you need, resized files and ready-to-paste picture markup.
1 Your layout 2 processed on your device 3 srcset + sizes
Responsive srcset Generator
Layout
Viewport
Image slot
Chosen width at 1x, 2x, 3x
Image and output
sizes
sizes attribute
Markup
<picture> markup
01
What it does
Works out sizes and the widths needed from your layout, resizes an image to AVIF, WebP and JPEG, and writes <picture> markup.
sizes attribute from breakpoints and layout widths
Widths needed for 1x, 2x and 3x screens
Resizes on this device to AVIF, WebP and JPEG
<picture> markup with width, height and loading
02
Private by design
Everything happens in your browser. Nothing you type, paste or upload is sent anywhere, and it keeps working offline once the page has loaded.
03
What you get
<picture> markup and a ZIP of resized images, with a Copy and a Download button on every result.
srcset
sizes
AVIF
WebP
Why it matters
Responsive images are one of the biggest performance wins and one of the most misunderstood features: the sizes attribute must describe the layout, not the image, and the widths in srcset should match the sizes the layout really needs on real screens.
This generator works both out from a description of your layout, then resizes the image on your device to each width in modern formats and writes the markup, including width and height so the layout doesn't shift.
How it works
InputHow wide the image shows at each breakpoint
In your browserWidths picked for 1×, 2× and 3× screens
Outputsrcset, sizes and a picture element
Where it fits in a designer's workflow
Plan
Design
Build
Test
Launch
Adding responsive images.
By the numbers
Chosen by this tool from 15 common screen widths at 1×, 2× and 3× pixel density, keeping a new size only when the last one would be too big, so every screen gets a file close to what it needs. The sizes attribute it writes: (min-width: 1280px) 400px, (min-width: 768px) calc(50vw - 2rem), calc(100vw - 32px). Source: MDN: responsive images.Show the numbers as a table
Width
330w
400w
480w
660w
800w
990w
1200w
How to use it
Describe the image's width at each breakpoint.
Choose screen densities and the size step.
Pick an image and the formats.
Copy the markup and download the ZIP.
FAQ
What's the sizes attribute for?
It tells the browser how wide the image will display, before the CSS loads, so it can pick the right file from srcset.
Why not just use 2x of the largest size?
Phones would download a desktop-sized file. Matching widths to the layout saves the most bytes on small screens.
Is AVIF always smaller?
Usually, by 20 to 50 percent against JPEG. Some browsers can't create AVIF, so the option is off if yours can't.
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