Hacker News Discussion Button od Jacob Strieb

This Firefox extension links to the Hacker News discussion for the current page and preserves privacy with Bloom filters.

When you visit a website, this browser extension determines whether the website has been submitted to Hacker News. If the current page has been on Hacker News, the extension lights up and becomes clickable. Clicking it retrieves a link to the best discussion for the page and navigates the browser there.

This extension uses a data structure called a Bloom filter to protect your privacy. Bloom filters can be thought of as a super condensed representation of the fingerprints of a long list of URLs. In this way, you can download the Bloom filter once (with periodic updates), and check if it contains the current website's URL fingerprint without making any requests over the Internet.

Read more about it here.