LaTeX in a link shows how web tools should talk to agents

Simon Willison published a web based LaTeX renderer that displays a single equation with MathJax or a full document with faster-latex. Source can be written in the editor, loaded from a URL or GitHub Gist and shared as a readable or compressed link.

The document fits inside a URL fragment and opens without an account

The tool stores LaTeX in the part of the address after the # character. A user can therefore save or send a link that restores both the source and its rendered form when opened. For longer content, it offers compression through Pako 2.1.0 and a dictionary tailored to LaTeX.

Willison took inspiration from Tiny Little Office and its documents stored in links. Claude Code using Opus 5.5 Extra received successive prompts for the editor, compression, URL and GitHub Gist loading and XSS protection. The resulting page uses MathJax 4.1.3, faster-latex 0.3.1 and DOMPurify 3.4.16.

The link acts as a small API for both people and agents

A conventional document editor hides state in an account, database and internal format. Here, the address carries that state. An agent does not need to operate an unfamiliar UI or gain storage access. It only needs to know the link format and encode the content correctly.

That makes this a useful design pattern for small web tools. The output is a document, a rendering instruction and a sharing mechanism at the same time. Tiny Little Office also describes its format in llms.txt, giving an agent machine readable guidance for constructing the result.

A shareable link does not settle whether its contents are trustworthy

Willison put the renderer in a sandboxed iframe and added DOMPurify to address XSS. Those controls matter because the tool accepts content from links, URLs and Gists. A sandbox still does not replace scrutiny of dependencies and future changes. Every new loading path expands the surface the author must defend.

Durable links and hostile input tests will determine its value

Two signals matter next: whether links created today still open after library upgrades and whether tests keep untrusted LaTeX isolated from the parent page. If both hold, this becomes a lightweight publishing format that people and agents can use without another account or integration.

Lilith's verdict

The agent does not have to wrestle with someone else's interface. It gets an address, assembles the document and lets the browser turn the link into a page.