My concern here is that by gravitating to HTML you lose the ability for a human (you!) to easily co-author the document with the LLM. If it’s just an explainer for your consumption, that’s not a concern - but if it’s a spec sheet for something more complex, I deeply value being able to dive in and edit what is produced for me. With a HTML doc it is much harder to do that than with MD.
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.
I suppose that only applies if you constrain yourself to a raw teletypewriter emulator… in any proper coding environment, editing HTML should be absolutely simple - even an embedded WYSIWYG editor would be an option if rich model output is a way we head into.
We have been authoring HTML by hand for decades with ease. Text editors are very good at it, and many have commands to auto-wrap, auto-close etc. Reading and writing is simple.
~html has more capabilities than markdown~ the real title
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…
When exploring a new idea or tool, my go to prompt is
```
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!"
Same. When I iterate on a design for a new client, I create a simple index.html with inline CSS and when I'm satisfied with the result I take the file and insert it next to my project template files and just ask the LLM to take the design from index.html and work it in the template files.
I never really thought about this use case before, and I feel a bit dumb because of that. It’s so obvious that it would be useful. My focus with LLMs so far has been on The App, not all the ancillary stuff around The App. All that ancillary stuff doesn’t have to be fully complete or polished and doesn’t have to handle every possible case. It just needs to be functional enough to be useful. When you’re done with it, throw it away and generate a new one tomorrow.
Web technologies got so many things right. People complain about it so much but it's amazing.
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.
> I’ve started preferring HTML as an output format instead of Markdown and increasingly see this being used by others on the Claude Code team, this is why.
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.
A couple of tradeoffs I don't see mentioned here for HTML vs MD:
- HTML is significantly less token-efficient
- Difficult to provide precise feedback on plans HTML, much easier to do this in MD.
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.
We’ve been doing this for a couple of months at work for internal memos and decision records, it’s really powerful. I love being able to drop in interactive visuals and more dynamic content. We have a Cloudflare R2-backed Document Store for managing them, and CLI for publishing, and I’m working on an MCP server for long-term discovery and context.
My team kept asking if they could leave comments though, so I built Annotent [1] to help with that, which is also MCP-backed.
Have we gone full circle? From the invention of HTML to the rebirth of plain text with MD to the rediscovery of HTML anbrhe age of LLM?
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 feels like a word salad that's been created to hit a word target because it's also LLM generated. Really not worth spending 5-10 minutes reading some "AI" output.
I'm thinking of adding support for GitHub-flavored markdown (including things like Mermaid diagrams) in my agent wrapper tool and then adding something like a skill for Claude Code to always write GitHub-flavored markdown and use its features when communicating with me. Seems a lot better than general Markdown.
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.
For similar reasons, I strongly prefer org-mode to markdown. I find that with org-mode and extensions (such as in-line elisp) I have a _significantly_ more powerful system. For example, specs can have tasks and roadmaps inline which reduces risk of drift. The biggest downside is, unfortunately, not enough folks are emacs proficient.
I hadn't considered HTML and I'm definitely going to try this.
I don’t think the idea of generating HTML is a novelty. Anyone using an LLM to create a web app has done that. Any “novelty” here is the idea of favoring HTML rather than Markdown for internal docs like specs, design docs, etc. Maybe you were already doing that. I sure haven’t been. In hindsight it’s obvious that it would be useful in some circumstances. Previously, I’ve had a bias against HTML because it’s annoying to read in a text editor.
So the argument seems to be that HTML is stronger than Markdown for disposable UI, visualization, and interactive artifacts. It also works well as an external memory object because it can be linked to and opened directly.
For visualization and animation, I do think HTML can be a very good format.
If LLMs become part of the workflow, this can definitely be useful. But on the other hand, maintaining HTML itself is more annoying than it first appears.
I do something somewhat similar. I download good CodePen examples and store them in a GitHub library so I can reuse them later. It works, but version management becomes quite difficult in practice. So I think there are real tradeoffs.
Yeah, I agree with this. I've been doing the same thing. Whenever I have to do a review, I ask the llm to create a dashboard. It's a godsend for reducing cognitive burden.
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.
I’ve been prompting my way to all kinds of interactive HTML artifacts the last month or so. It’s way more fun than making decks and static documentation.
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. ^_^
I guess the author has never heard of Markdown editors with a preview feature, and doesn't know that the Claude Code VS Code plugin opens plans in preview mode.
I've felt the opposite. With MD being the preferred planning+documentation output for LLMs, the time of "hype" seems to be now. It seemed just a few years ago that devs hated writing properly formatted markdown.
It's been confusing to me that so many people have treated markdown as the lingua franca for agent instructions when their training corpus must be dramatically biased to HTML instead of Mardown.
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.
Do we have local first html renderers that don’t complain about cors and wrong file addresses? I don’t want to spin up a server just to open an HTML file
Feels like markdown is token-efficient since its abbreviating HTML tags. Think about a large table. Also, HTML can't be especially rendered inside, say, Neovim, so now interacting with an LLM interface gravitates towards GUIs. Good for accessibility, I guess, there's that. Maybe the need for token efficiency will finally realize my dream of writing Slim[0], or some such, straight to the browser, full native compat.
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.
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…
``` 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!"
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.
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.
0. https://daringfireball.net/projects/markdown/
Using bots has been insane and self-referrential.
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.
My team kept asking if they could leave comments though, so I built Annotent [1] to help with that, which is also MCP-backed.
1. https://www.annotent.com/
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”.
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!
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.
I hadn't considered HTML and I'm definitely going to try this.
For visualization and animation, I do think HTML can be a very good format.
If LLMs become part of the workflow, this can definitely be useful. But on the other hand, maintaining HTML itself is more annoying than it first appears.
I do something somewhat similar. I download good CodePen examples and store them in a GitHub library so I can reuse them later. It works, but version management becomes quite difficult in practice. So I think there are real tradeoffs.
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.
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. ^_^
In turn, chatbots pump up markdown by making it the default output format.
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.
[0]https://slim-template.github.io/