Disabled JavaScript turns off native lazy loading

Written by Stefan Judis
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This post is part of my Today I learned series in which I share all my web development learnings.

It's speedy TIL time! Did you know the loading="lazy" attribute doesn't work when you turn off JavaScript?

Now, you do. 😉

Why doesn't lazy load work without JS? There's only one reason why we can't have nice things: of course, it's for tracking prevention.

Here's the loading MDN documentation explaining the behavior:

Loading is only deferred when JavaScript is enabled. This is an anti-tracking measure, because if a user agent supported lazy loading when scripting is disabled, it would still be possible for a site to track a user's approximate scroll position throughout a session, by strategically placing images in a page's markup such that a server can track how many images are requested and when.

And if you really want to get into this topic, here's the related spec describing when loading="lazy" should work.

And just to be clear, because some folks were confused: images will still load when JS is disabled. It's only the deferred loading that won't work.

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About the author

Stefan standing in the park in front of a green background

Frontend nerd with over ten years of experience, "Today I Learned" blogger, conference speaker, Tiny helpers maintainer, and DevRel at Checkly.