Related: https://simonwillison.net/2026/May/8/unreasonable-effectiven...
Now of course you could just reprompt your LLM to change the HTML - but when I already have a clear idea of what I want to say in my head, that’s just another roadblock in the way.
If this pattern becomes more common I suspect human/LLM co-creation will further dwindle in favour of just delegating voice, tone and content choice to the LLM. I was surprised not to see this concern in the blog post’s FAQ.
Even after React became popular, people are still manually typing out HTML elements, although they call it "JSX" instead, but in reality it's just HTML.
My first blog on the internet literally was a bunch of .html files, where my post "template" was the first post copy-pasted when you wanted to make a new post. Changing the design involved changing the same thing across all files.
No, we've been generating it with templates or authoring templates.
Authoring HTML by hand is a very early 2000s thing to do.
I think most of us live somewhere in the middle, using the right tool / output for the job.
It's arguable even more readable.
<b>bold</b> <i>italic</i> <u>underline</u>
I can never remember how many stars and ticks correspond to what in markdown.
"No bread? Let them eat cake!"
To me it feels like a worse experience, and they probably feel it too, but it makes sense from an optimization perspective. I've probably learned some shell tricks, but also going blind from watching Claude try dozens of variations of some multi-line chained and piped wall of bash nightmare, instead of just reading a few files.
It also gives tips on reducing context size when you run /context .
Presumably they are actually starting to feel the pinch on inference costs themselves with what still feels like a fairly generous max plan.
Also: https://platform.claude.com/docs/en/agents-and-tools/tool-us...
*No!*
I mean, <b>yes!</b>
2. One of the limiting factors of LLM is context. An html table takes up way more tokens than a markdown table. Especially if it's a WYSIWYG editor that has all kinds of css and <span> tags just for fun.
Arguing for html on a platform with less rich semantics than markdown is just ultimately funny
``` In a single index.html, no dependencies, sparse styling, create an app that <idea> ```
Even before AI, it's how I built small tools, and there's something lovely about being able to email my friends the tool, and tell them "If you want to make a change, toss it to your LLM!"
It is incredible how far you get with a single HTML-file, containing styles and JS, when building dashboards, small apps and other utilities that can interact with an API or otherwise fetch data from somwhere.
I just drop it on my personal ~ folder on the shared server at work and voilà, everyone can check it out and use it immediately!
For the most parts you just write the regular Markdown headers and paragraphs, embed images, insert tables etc without the need for any HTML tags, making it readable in source form. And if you want to embed an SVG file for example, which the author of the article mentions as one use case, you just embed the SVG directly, and people can render the Markdown in their favorite viewer.
Let's say you're viewing a raw Markdown file in VS Code. You come onto an HTML tag, so you hit Cmd+Shift+V to open the preview and that's it.
Of course for full-fledged web pages with interactive buttons and fully customized styling and all of that, which the author shows in some examples, this is not feasible. But you can get very far when you have mostly text/images/tables and just want to add some extras here and there.
[1] https://daringfireball.net/projects/markdown/syntax#html
I worked with a vibe coded app at my last job (and since quit due to it) and because it was a nextjs SPA frontend with a separate API backend, the user facing urls didn't match the backend endpoints. Because AI uses react hooks for everything, state is in-memory, url-based routing isn't a thing unless you design for it. So links aren't free and thus we have no way for users to link to anything other than top-level entry points. LINKS! Especially for internal tools, everything being linkable is vital to collaboration and problem solving.
The need for uniform resource locations and verbs was so well thought out, 30 or 40 some odd years ago.
What i learned, by fire, is that nextjs works well with its nested routing and layout-to-hold-context magic. it's quite nifty but it's not free and not obvious, you have to design for it. I can't state enough that AI will ship a billion hooks, it loves hooks for self-contained state. My colleague made a good point that that style is a feature; it limits blast radius of N features all building on top of each other.
Yeah i had to move on from there.
Is it really unreasonably effective?
While it has been used in the context of HTML before, it's a bit of a "meme" as several papers used that phrase. Much like the "X is all you need" snowclone.
The HTML version dates from 2021 (https://shkspr.mobi/blog/2021/01/the-unreasonable-effectiven...) when client side rendering and web apps were still their peak.
I also love how maybe 10% of the posts on here are like "some thing that has existed for 40+ years ,/:/; Claude/chatgpt". So much advertising at the expense of a dead internet it's ridiculous.
Both of these tradeoffs set Anthropic up for success. Using HTML as our medium will increase token usage, and I'd bet they're investing in tools to mark up HTML (part of Claude Design) which will help improve lock-in. Either coincidence or brilliant strategy.
This is why I read long agent output either by using VIM and MacOS Quicklook (with a markdown extension for rendering) or paste output into MarkEdit (an editor with a preview pane; I think it’s cross platform?). Worst case, have an agent build you a simple local web page that interprets Markdown and renders it. Markdown was invented as a shorthand for web syntax[0]. That’s what it’s for! I bet you spend more tokens and time asking an agent to convert its native markdown to html than any of these.
Using bots has been insane and self-referrential.
The most important thing is that I can run static analysis on a structured format. This is important even for my spec documents. I can write data fields and have static analysis analyze it. For example, to confirm database fields match across various spec documents, etc.. The static analysis is also why you use JSON/XML instead of HTML, since you can now have your own custom schema.
Also don't use YAML, as that's far more unreliable. (If you chop a YAML file in half, it's still valid)
Sure enough, this is full of listicles and of a length no human would write for an idea as simple as "Use HTML instead of Markdown."
I'm also not convinced that it solves meaningful problems :
> I've found I tend to not actually read more than a 100-line markdown file, and I certainly am not able to get anyone else in my organization to read it. But HTML documents are much easier to read, In my experience, LLMs are not concise when it comes to documentation, so using an easier file format to read because the text is too large sounds to me like solving the wrong problem
> Markdown files are fairly hard to share since most browsers do not render them natively well. Yes, but developers tools (IDE, Git forge) do. What most/some of them don't render natively IS HTML.
Presumably you mean rendered HTML rather than the source documents?
I have been building a slightly different solution to the same problem. So far I’m pretty happy with the results and I have enough returning users that I think others are too (https://sdocs.dev/analytics).
I’ve built SmallDocs (https://sdocs.dev; Show HN: https://news.ycombinator.com/item?id=47777633).
SDocs is cli (`sdoc file.md`) -> instantly rendered Markdown file in the browser
When you install the cli it gives you the option to add a note in your base agent file (`~/.claude/CLAUDE.md`, etc.). This means every agent chat knows about SDocs and you can say “sdoc me the plan when you’re done with it” and the file will pop open instead of you having to find that terminal session to know it’s done.
Going browser first means you’re not required to install anything to get a great experience.
Despite being in the browser, the content of SDocs rendered Markdown files remain entirely local to you. SDoc urls contain your markdown document's content in compressed base64 in the url fragment (the bit after the `#`):
https://sdocs.dev/#md=GzcFAMT...(this is the contents of your document)...
The url fragment is never sent to the server (see https://developer.mozilla.org/en-US/docs/Web/URI/Reference/F...: "The fragment is not sent to the server when the URI is requested; it is processed by the client").
The sdocs.dev webapp is purely a client side decoding and rendering engine for the content stored in the url fragment.
This also means you can share your .md files privately by sharing the url.
To go a bit deeper towards the HTML side of things I’ve added tagged code blocks that the agent is given documentation on how to use. Eg ```chart or ```mermaid (for mermaid diagrams). These then become interactive elements on the page (mermaid is best example of this currently)
I hadn't considered HTML and I'm definitely going to try this.
I even did a workshop with PartyKit cursors, dot voting, reflection comments, and an individual rating at the end.
Oh, and I can add super lightweight analytics so I know who actually reads my things or interacts with my prototypes. ^_^
It ended up being a large document but it was infinitely more useful than plain old markdown. I think I’ll do it more often now. Creating interactive specs is a really fascinating way to work. I’ve always verified my work in similar ways, but this was more… Verification-forward, I guess. And it took hours instead of days.
It’s actually really fun to be building and refactoring these days. No idea how long the fun will last, but I’m thoroughly enjoying it right now. I know it will make some people think I’m a hack, but I know that approach enabled me to do a faster, more targeted, ultimately better job of improving state management in the application. It’s not because Claude wrote the code (I still did quite a bit of it), but because Claude helped me establish the right work to do for the right reasons, using tools I couldn’t dream of throwing together 5 years ago.
Though now I'm wondering: why not just add full HTML embedding support as well? I'm talking not just for specific deliverables, but for any of the agent's responses with the user.
The facts that this article needs to list the pros of HTML over MD, like inreraction, visual density, etc, is weird to me. Maybe the ahdience is not tech-savvy people but I read it as an unnecessary word salad.
It is just realization by author that HTML is also useful tool and MD lacks some stuff.
He didn’t write anything about “now we should stop using MD files”.
It is more like: “I see I can do cool stuff with HTML and found cases where it definitely is right tool for the job”.
What happens when my site changes style, I put it back through the LLM I guess and get some bonus hallucinated content.
Apologies if I'm slightly demeaning here, but what? Markdown is largely plaintext. Unless the output is completely littered with markdown formatting (specifically, imo, tables and maybe links would be the hardest for a human to parse), is this not just saying "I have a difficult time reading large bodies of text" (which is of course fine - people prefer different ways ingesting information)
From reading the post, this seems like a "I personally prefer more visual, interactive elements in output" rather than "agents using markdown leads for less understandable output", and not at all what I would recommend for the average person to use unless said agent or interface or whatever had an extremely seamless way of displaying the HTML. If I had to open the agents response in a browser every time I wanted anything detailed I would lose my mind.
I've certainly had agents generate more rich visualizations such as through html, but I can't imagine using that as my default.
Surely a html page could do the same but I would see that as the last step, to give to someone else.
To review PRs in a little custom app is a very good idea. Who cares about 1.2x more tokens when clarity is squared?
Nice article!
Classical overly confident llm bullshitting.
My team kept asking if they could leave comments though, so I built Annotent [1] to help with that, which is also MCP-backed.
I think the reason stuff like this wasn't done earlier was due to fears about context pollution, but post training has gotten so good that you can do virtually anything in the context window and not have it affect the quality of output.
Markdown only makes sense for us meatbags becuse it's easy for us to edit and version control, but if you're sharing anything where the audience is an agent publicly, HTML must be just as interpretable.
Weren’t llms specifically originally set to output and print markdown format since it is simpler and easier everyone to read? No different rendering/libraries/apis to worry about…
If you rename a .html file to .md, your markdown viewer should render it just the same as your browser did.
In turn, chatbots pump up markdown by making it the default output format.
This is the sort of observation that should make you concerned about your own skills, rather than spur you to generate an article (longer than you can read easily) trying to give advice to other people.
The linked article could have been made using Markdown, and yet the author still chose to represent themselves this way; there's no point changing the tool when the problem is the user.