4chan vs HackerNews

4chan's API serves the same read-only board and thread data every page renders — board lists, catalogs, threads, and posts — as plain JSON from the dedicated a.4cdn.org host, with no registration, key, or authentication of any kind required. Media referenced by posts is served from the sibling i.4cdn.org host, and the project's own GitHub repository (4chan/4chan-API) hosts the reference client and doubles as the canonical documentation, including the rule to cap requests at one per second. Cross-origin use from a browser is limited in practice: both the docs and a live probe confirm the API's CORS policy only allows requests originating from 4chan's own board pages, so a third-party site must proxy requests server-side rather than call it directly from client-side JavaScript.

The official Hacker News API is a read-only Firebase-backed REST feed publishing items (stories, comments, jobs, polls) and user profiles as simple JSON, with helper endpoints for the current top/new/best/ask/show/job story ID lists. It requires no API key or registration, updates roughly every 30 seconds to reflect live site activity, and has stayed structurally unchanged since Y Combinator open-sourced it in 2015.