Anthropic engineer: HTML is Claude Code’s best output format, not Markdown

Anthropic Claude Code team engineer Thariq Shihipar published on May 8 “Using Claude Code: The Unreasonable Effectiveness of HTML,” arguing that HTML should replace Markdown as the output format for interacting with Claude Code. Simon Willison summarizes the key points: HTML provides SVG charts, interactive components, in-page anchors, and CSS styling—turning Claude’s answers from “linear text” into a “multidimensional document,” which can significantly improve reading and comprehension efficiency. This topic is extremely hot on the X platform—Shihipar’s two related posts have combined for more than 15,000 likes.

Core argument: HTML offers visual and interactive capabilities that Markdown can’t

Shihipar’s reasons for why HTML beats Markdown:

Richer visuals: SVG charts, color-coded elements, styled callouts

Interactivity: native support for widgets and dynamic components

Navigation: in-page anchors and structured information hierarchy

Professional formatting: CSS styling improves clarity and aesthetics

Markdown became the standard mainly because early LLMs had relatively small context windows (e.g., the GPT-4 8K era), forcing developers to save tokens; HTML tags themselves consume more tokens than Markdown, so in the small-context era it wasn’t worth it. After Claude entered the 200K to 1M context era, token cost is no longer the limiting factor, and HTML’s visual advantages can be fully leveraged.

Concrete use case: generating dark-theme technical documentation with HTML when analyzing Linux vulnerabilities

Shihipar uses Linux security vulnerability analysis as an example:

Markdown output: plain text, relying on indentation and heading-based layering

HTML output: dark-theme technical documentation, severity levels with color encoding, side-by-side comparison tables, and warning callout blocks

Reader experience: the HTML version makes technical content hierarchy, severity, and comparison relationships instantly recognizable

With the same information content, the readability and actionable value of HTML output far surpass the Markdown plain-text version. In scenarios that require producing “explanations for people” (not “plain text for machines”), HTML is the better choice.

Recommended usage: explicitly require complete HTML + CSS + JS capabilities in the prompt

Shihipar recommends the following prompt pattern:

“Output HTML—use HTML, and leverage the full capabilities of HTML, CSS, and JavaScript to make the explanation rich, interactive, and clear”

Suitable for: technical documentation, teaching explanations, data visualization, interactive reports

Not suitable for: purely code files, structured data (still use the corresponding format)

Specific events to follow up: whether Anthropic will officially recommend HTML output capabilities to Claude Code users, whether other IDE/agent frameworks (Cursor, Codex) adopt a similar output format, and how the long-term adoption rates of Markdown vs HTML change in the developer community.

This article: Anthropic engineer—HTML is the best output format for Claude Code, not Markdown—earlier than in the chain-news ABMedia.