There really isn’t. For example web browsers can execute assembly now and a good “web developer” (I’d call them a software engineer) will use assembly where appropriate.

“web development” casts a wide net.

The classic imagery of someone playing with frontpage back in the day, or screwing around with html in a text editor, sure. But those folks wouldn’t call themselves web developers (there was a phase over 20 years ago where anyone that cobbled together a geocities would declare ‘web developer’ on their resume, but I haven’t seen someone do that in ages).

However, you can get in pretty deep with code running in the browser as javascript and/or wasm. Backend gives them some nested dictionary in json or protobuf and they parse, manipulate, iterate over it, sometimes making some pretty complex visualizations. Basically a ‘web developer’ is nowadays on par with any Game or GUI application developer in terms of what they might be writing. There are a few things left out of direct reach by a browser runtime, but you have access to plenty and the backend abstractions to get something in reach of HTTP are often no easier than the thing being abstracted, it’s just reframed as ‘http’.