Half the value of a dense article lives in the terms you almost understand. You scan past them because stopping costs too much — new tab, search, read, return, lose your place, repeat. After a few of those you stop bothering and accept a shallower read than the piece deserved.
rabbitholes is a Chrome extension that lets you highlight any text and get an inline explanation rendered in a shadow-DOM tooltip next to your cursor — no new tab, no page pollution. The explanation comes from Claude Haiku 4.5. Click any word in the response to explore it further, or drag across a phrase to treat it as a new query.
Two things make it less like a dictionary lookup and more like actually following a thread:
First, every answer surfaces two suggested rabbit-hole topics — the most interesting threads branching from wherever you are. One click continues without breaking your reading context.
Second, a globe icon re-runs the query enriched with Brave Search results. If you're reading about a recent event or a contested claim, you get source chips alongside the explanation, clickable without leaving the page.
A rabbit-hole counter tracks how many hops deep you've gone. If you chase a chain far enough to land on philosophy — the Wikipedia game — you get a shareable trail of the path.
No intermediary server. Requests go directly from your browser to api.anthropic.com and api.search.brave.com. Zero telemetry, Manifest V3, API key stored in chrome.storage.sync.
// The shadow DOM approach: explanations attach to document.body via
// a closed shadow root so host-page CSS can't bleed in or out.
const host = document.createElement('div');
const shadow = host.attachShadow({ mode: 'closed' });
document.body.appendChild(host);
That boundary matters: iframes would've required cross-origin gymnastics and still couldn't match host-page font rendering reliably. Shadow DOM keeps the tooltip visually coherent across Wikipedia, Substack, arxiv, wherever you're reading.
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