4ort.xyz: the Popularity Graph.
A free, open knowledge base of 41,034,760 entities and 30,923,552 relationships, mirrored from Wikidata under CC0 and kept current via the Wikipedia EventStreams firehose. Entities are ranked by real Wikipedia pageviews, so the most-read facts surface first. Every claim has a citation. Every property has a confidence signal. Edits are logged with current-value context that explains what actually changed.
The data is structured for LLMs and AI agents at every level. Entity pages expose JSON-LD with Article, FAQPage, and Claim markup; ship a plain-markdown alternate at /entity/{slug}.md for low-token retrieval; declare AI-crawler friendly status at /llms.txt; and are queryable via a versioned v1 REST API at /api/v1 covering entity GET, hybrid search, fuzzy match, popularity, trending, RAG-style Q&A, and bundled context recipes that pre-pack relevant facts for SEO writers and agents in a single request. An MCP server is on the roadmap so Claude Desktop, Cursor, LibreChat, and other MCP clients can call every API directly as a tool.
Use cases stack up. SEO writers ground articles in cited facts. Daily-news services report what changed in a country today. AI assistants cite primary sources on every factual answer. Investment platforms cross-reference companies to SEC filings. Knowledge management tools build agent memory banks from authoritative public-domain data that is free to redistribute and verifiable to the source URL.