OneImage

Responsive images generator

Generate srcset image sizes for faster web pages

Create multiple image widths for responsive layouts in one batch. Export common breakpoints and copy-paste HTML or Next.js code directly into your project.

Local processing — no uploads

Generate responsive images

Upload an image and select output sizes. Choose scale ratios, breakpoint widths, or add custom dimensions.

Tip: Start with a high-resolution source image for the sharpest results across all sizes.

Scale ratios

Generate images at different scale factors relative to original size

Responsive breakpoints

Common viewport widths for srcset — select the sizes you need

Custom widths
Output

5 sizes selected

Responsive images let browsers pick the right size for each device, improving load times and Core Web Vitals. This tool generates common width variants from a single source image.

Upload once, export 320px through 1920px sizes, and get ready-to-use srcset markup. Everything runs locally—your images stay private.

Multiple breakpoints at once

Generate 320, 640, 960, 1280, and 1920px widths in a single batch export.

Copy-paste code snippets

Get HTML srcset or Next.js Image markup ready to drop into your codebase.

Optimized for LCP

Serve appropriately-sized images to boost Largest Contentful Paint scores.

Recommended responsive breakpoints

Common widths that cover mobile, tablet, and desktop viewports.

320px
Small mobile (portrait)
640px
Large mobile / small tablet
960px
Tablet landscape
1280px
Small desktop / laptop
1920px
Full HD desktop

How to generate responsive images

Create optimized image variants for srcset in a few steps.

1

Upload your source image

Select a high-resolution JPG, PNG, or WebP. A larger source gives sharper downscaled results.

2

Add responsive sizes

Use the multi-size export to add 320, 640, 960, 1280, and 1920px widths.

Keep aspect ratio locked to preserve the original proportions across all sizes.

3

Process and download

Click Resize to generate every variant, then download each file or grab them all at once.

4

Copy the srcset snippet

Use the generated HTML or Next.js snippet to add responsive images to your pages.

When to use responsive images

Hero and banner images

Serve 1920px to desktops and smaller files to phones, slashing load times for mobile users.

Blog and article thumbnails

Generate multiple widths so readers on any device get a fast, sharp preview.

E-commerce product photos

Provide appropriately-sized listing images to improve page speed and conversion rates.

Features

Batch multi-size export

Add several widths and generate them all from a single source in one pass.

Aspect ratio preserved

Heights scale proportionally so images never stretch or squash.

Ready-to-use code

Copy HTML srcset or framework-specific snippets directly into your project.

Private and local

All processing happens in your browser. Images are never uploaded to a server.

Responsive images FAQ

How do I write the sizes attribute?

The sizes attribute tells the browser how wide the image will display at each viewport. For example, `(max-width: 640px) 100vw, 50vw` means full viewport width on small screens and half on larger ones. Match it to your CSS layout.

How many breakpoints should I use?

Five to seven widths covering mobile through desktop is a good default. More sizes add flexibility but increase storage. Start with 320, 640, 960, 1280, and 1920 and adjust based on analytics.

What about 2x retina images?

Browsers select from srcset by both viewport width and pixel density. If your largest source is 1920px, a retina phone might pick the 1280px version to get enough pixels. Provide higher widths if sharp retina rendering matters.

How does this help Largest Contentful Paint (LCP)?

LCP measures how fast the biggest visible element loads. By serving smaller images to mobile, you transfer fewer bytes and render the hero faster, directly improving your Core Web Vitals score.

Can I use these images with Next.js Image component?

Yes. If you self-host, place the files in /public and set the image sources accordingly. For more control, Next.js built-in loader can also generate sizes on the fly, but pre-generating can reduce server load.

Do I need to convert to WebP or AVIF?

Modern formats shrink file sizes further. You can convert in a separate step or use squoosh tools alongside this generator. Browsers that support the format will load smaller files while others fall back to JPG/PNG.

Open the image resizer

Ready to generate responsive images? Upload a photo and export multiple widths for your website.

Open the image resizer
Responsive Images Generator – Create srcset Sizes for Web | OneImage