Imagine opening this page on a slow phone connection. The media should still be worth the wait and have a sensible fallback.
What You Need to Know
A responsive-images audit checks what file actually loaded at different widths. Inspect the chosen source, image dimensions, alt text, and loading behavior rather than guessing from the HTML alone.
Try the Example
Take a look at the example. We’ll explain the important lines right below it.
<img src="images/city-800.jpg"
srcset="images/city-400.jpg 400w, images/city-800.jpg 800w, images/city-1200.jpg 1200w"
sizes="(max-width: 600px) 100vw, 50vw"
alt="City buildings at sunset" width="800" height="450">Let’s Read the Code
- <img>: The img displays a picture; its alt is the text alternative.
- src: Src identifies a resource path for images, frames, or media.
- srcset: Srcset offers image candidates for different displays or layout sizes.
Read the named elements and attributes together. They explain how the browser connects this feature to the rest of the page.
What Happens in the Browser?
The paths shown here refer to files in your own example project. Put real images and recordings in those locations before expecting them to load.
Which picture loads? With width descriptors, sizes describes the expected display width and srcset offers candidates. The browser can also consider screen density and network conditions. Inspect the selected source instead of assuming every screen receives the same file.
Your Turn
Resize the viewport and inspect the chosen image source in Developer Tools. Do not assume the browser always downloads the smallest file.
Common Beginner Mistakes
- Leaving out real media files or understandable text alternatives.
- Always check keyboard access, readable alternatives, and any missing files; a perfect player layout does not guarantee accessible content.
Key Takeaways
- A responsive-images audit checks what file actually loaded at different widths.
- <img>: The img displays a picture; its alt is the text alternative.
- If the resource cannot load, users still need enough text to understand what was meant to be there.