Web Bookmarking

1 Overview

A web bookmark is a saved reference to one web page. This NIP defines kind:39701 for web bookmarks. Each bookmark is one event. The bookmarked URI lives in the event's d tag.

Kind 39701 sits in the addressable range of NIP-01. A relay keeps only the latest event per pubkey + kind + d value. A user can therefore edit a bookmark. The user publishes a new event with the same d value, and the old version goes away.

Because the d value is the URI itself, clients can query bookmarks by URI. One #d filter returns every user's bookmark of the same page. This turns private bookmarking into a shared, social index of the web.

2 The Bookmark Event

A web bookmark is a normal signed event with kind:39701. The content field holds a detailed description of the bookmark. The description can be an empty string. The d tag is required. All other tags are optional metadata.

{
  "kind": 39701,
  "content": <description of the bookmark, may be "">,
  "tags": [
    ["d", <URI of the bookmarked page>],      // required
    ["published_at", <unix seconds, string>], // optional
    ["title", <title of the bookmark>],       // optional
    ["t", <topic>], ...                        // optional, repeatable
  ],
  // plus the standard id, pubkey, created_at, sig fields
}

3 The d Tag: One URI per Bookmark

The d tag value is the URI of the bookmarked page. One rule shapes the value. If the scheme is https, omit all characters before the hostname. Drop https:// and start the value at the hostname. For any other scheme, keep the URI as it is.

https://alice.blog/post      →  "alice.blog/post"   // https scheme dropped
http://old.example/page      →  "http://old.example/page"
gemini://caps.example/doc    →  "gemini://caps.example/doc"

This rule makes the d value predictable. Clients query web bookmark events by the d tag. A filter such as {"kinds": [39701], "#d": ["alice.blog/post"]} returns every bookmark of that page, from every user, on that relay.

4 Metadata Tags

Metadata fields can be added to the event as tags when necessary. This NIP names three:

5 Replies and Comments

Replies to a kind:39701 bookmark must use kind:1111 comment events, as defined in NIP-22. Do not reply with plain kind-1 notes. The NIP-22 comment carries scope tags that point back to the bookmark's address, so threads stay attached to the bookmark even after edits.

6 Worked Example

Alice bookmarks a blog post at https://alice.blog/post. The scheme is https, so the d value starts at the hostname. She adds a title, two topics, and a first-publication timestamp.

{
  "kind": 39701,
  "id": "d7a92714f81d0f712e715556aee69ea6da6bfb287e6baf794a095d301d603ec7",
  "pubkey": "2729620da105979b22acfdfe9585274a78c282869b493abfa4120d3af2061298",
  "created_at": 1738869705,
  "tags": [
    // required tags
    ["d", "alice.blog/post"],
    // optional tags
    ["published_at", "1738863000"],
    ["title", "Blog insights by Alice"],
    ["t", "post"],
    ["t", "insight"]
  ],
  "content": "A marvelous insight by Alice about the nature of blogs and posts.",
  "sig": "36d34e6448fe0223e9999361c39c492a208bc423d2fcdfc2a3404e04df7c22dc65bbbd62dbe8a4373c62e4d29aac285b5aa4bb9b4b8053bd6207a8b45fbd0c98"
}

A reader now queries the relay for every bookmark of that page. Later, Alice edits her description. She republishes with the same d value, and the relay replaces the old event.

-- Alice publishes the bookmark --
→ ["EVENT", {"kind":39701, "id":"d7a92714…", "tags":[["d","alice.blog/post"], …], …}]
← ["OK", "d7a92714…", true, ""]

-- a reader looks the page up by its d value --
→ ["REQ", "bm", {"kinds":[39701], "#d":["alice.blog/post"]}]
← ["EVENT", "bm", {"kind":39701, "pubkey":"2729620d…", "content":"A marvelous insight…", …}]
← ["EOSE", "bm"]

-- Alice edits: same d value, newer created_at --
→ ["EVENT", {"kind":39701, "id":"4c01afe2…", "created_at":1738900000,
     "tags":[["d","alice.blog/post"], ["published_at","1738863000"], …],
     "content":"Updated notes on Alice's post.", …}]
← ["OK", "4c01afe2…", true, ""]  // relay now serves only this version

7 Version History

NIP-B0 is young and small. Its one substantive revision fixed how schemes are handled in the d value. Notable changes, newest first:

• 20262026-07Fixed the URI scheme ambiguity: only the https scheme is omitted from the d value; other schemes stay verbatim. A misapplied suggestion from the same change was corrected the same day.
• 2025-262025-08Wording cleanup and code-fence relabeling passes.
• 20252025-04Renamed to the uppercase B0.md filename shortly after merge.
• Origin2025-04-24Sebastian Hagens proposed kind:39701 web bookmarks in PR #1849.

8 See Also

• NIP-01 — addressable events, the d tag, and #d filters that this NIP relies on.
• NIP-22 — kind:1111 comments; the mandatory reply format for bookmarks.
• NIP-51 — bookmark lists (kind:10003); many references in one event, instead of one event per URI.
• NIP-73 — external content IDs; another way to reference web URLs from events.