Backlinks

How two-way links work in OP — how to create them and how to endorse incoming ones from other sites.

Last modified 2026-05-01

Table of content
  1. Creating a backlink
  2. Endorsing incoming backlinks
  3. Webrings
  4. Current limits

A backlink is a link both sites know about. When your page links to another and that page acknowledges it, the connection is two-way — both sides can display and query it.

Hashtags work this way on closed platforms: tagging a post links it to a tag page that aggregates all posts with that tag. OP backlinks work the same way without the middleman. You link to a page, that page knows you linked to it, and any OP server connected to both can reflect that relationship.

Add rel="octo:octothorpes" to any outgoing <a> or <link> element:

<a href="https://somecoolurl.com/cats" rel="octo:octothorpes">Read about cats</a>

This tells your connected OP servers that your page links to that URL. You can stack other rel values alongside it as usual.

Registering a backlink on your end doesn't complete the relationship on its own — the target site has to endorse it. This is intentional: no one gets silently linked to without consent.

To endorse incoming links from a specific origin, the target site adds a <link> element with rev="octo:octothorpes" to their page <head>:

<link rev="octo:octothorpes" href="https://originating-site.com">

Once that's in place, OP servers register the relationship. The target site can then query any connected OP server for backlinks to its pages and display them however it wants.

To endorse backlinks from any site connected to your servers, use a wildcard:

<link rev="octo:octothorpes" href="*">

rev is a deprecated HTML attribute originally proposed to denote reverse links. OP brings it back deliberately — it's the right semantic fit for this use case.

Webrings

Webring membership is a natural application of backlinks. Linking to a webring page with rel="octo:octothorpes" registers your site as a member:

<a rel="octo:octothorpes" href="https://some-webring.example.com/webring">Member of Some Webring</a>

If the webring page endorses incoming links, it can query its OP server for all backlinks to that URL and display its member list dynamically — no manual roster to maintain.

Current limits

Endorsement currently works at the domain level. Endorsing originating-site.com endorses all pages from that domain. Finer-grained moderation controls are planned.