Srcset is an HTML attribute used to specify multiple image sources for different screen sizes and resolutions. It allows the browser to select the most appropriate image based on device characteristics such as viewport width and pixel density. This improves image loading efficiency and visual clarity across devices.
Instead of serving a single image to all users, srcset enables responsive image delivery. Smaller devices receive lighter images, while high resolution screens receive sharper assets. This reduces unnecessary data transfer and improves page performance without sacrificing quality.
Srcset is a core component of modern responsive design. When implemented correctly, it enhances user experience, supports performance optimisation, and aligns with best practice for mobile and multi device websites.
Advanced
Srcset works in combination with the sizes attribute to inform the browser how much screen space an image will occupy. The browser evaluates available sources and chooses the optimal file before downloading. This decision happens automatically and efficiently.
Advanced usage requires accurate size definitions and consistent image generation. Poor configuration can result in oversized downloads or blurry images. Srcset is most effective when paired with modern formats, compression, and performance monitoring.
Relevance
- Improves image loading performance.
- Enhances visual quality on high resolution screens.
- Reduces unnecessary data transfer.
- Supports responsive and mobile friendly design.
- Contributes to better page experience signals.
Applications
- Responsive website images.
- Mobile performance optimisation.
- High resolution display support.
- Ecommerce product imagery.
- Media heavy content layouts.
Metrics
- Image load time improvements.
- Page weight reduction.
- Largest Contentful Paint impact.
- Mobile performance scores.
- Bandwidth usage trends.
Issues
- Incorrect sizing causes oversized downloads.
- Missing sizes reduces effectiveness.
- Inconsistent image generation creates blur.
- Poor testing leads to regressions.
- Legacy browsers require fallback handling.
Example
An ecommerce site implemented srcset for product images across mobile and desktop. Mobile users received smaller images, load times improved, and visual quality remained high on large screens, contributing to better engagement and conversion rates.