alt Hacker NewsHTML becomes pretty delightful for prototyping when you embrace this. You can open up an empy file and start typing tags with zero boilerplate. Drop in a script tag and forget about getElementById(); every id attribute already defines a JavaScript variable name directly, so go to town. Today the specs guarantee consistent behavior so this doesn't introduce compatiblity issues like it did in the bad old days of IE6. You can make surprisingly powerful stuff in a single file application with no fluff.
I just wish browsers weren't so anal about making you load things from http://localhost instead of file:// directly. Someone ought to look into fixing the security issues of file:// URLs so browsers can relax about that.
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Love the single file html tool paradigm! See https://simonwillison.net/2025/Dec/10/html-tools/
Opus and I have made a couple of really cool internal tools for work. It's really great.
Wow, I had never heard of that ID -> variable feature
I liked learning this so much that I created a VSCode Extension to enable goto clicking and autocomplete and errors for single page html files and type hover so I can properly use it when i am prototyping.
https://marketplace.visualstudio.com/items?itemName=carsho.h...
> Someone ought to look into fixing the security issues of file:// URLs
If you mean full sandboxing of applications with a usable capability system, then yeah, someone ought to do that. But I wouldn't hold my breath, there's a reason why nobody did yet.
Yes i love quickly creating tools in a single file, if the tool gets really complex I'll switch to a sveltekit Static site. I have a default css file I use for all of them to make it even quicker and not look so much like AI slop.
I think every dev should have a tools.TheirDomain.zzz where they put different tools they create. You can make so many static tools and I feel like everyone creates these from time to time when they are prototyping things. There's so many free options for static hosting and you can write bash deploy scripts so quickly with AI, so its literally just ./deploy.sh to deploy. (I also recommend writing some reusable logic for saving to local storage/indexedDB so its even nicer.)
Mine for example is https://tools.carsho.dev (100% offline/static tools, no monetization)
A workaround for the file:// security deny is to use a JavaScript file for data (initialized array) rather than something more natural like JSON.
Apparently JavaScript got grandfathered in as ok for direct access!