# NIP-74: Nostr Link Lists

`draft` `optional` `author:vveerrgg`

This NIP defines a standardized format for sharing curated lists of links on Nostr. The NIP number 74 was chosen as it represents the ASCII character 'L' (for Links).

## Abstract

Link lists are collections of URLs with associated metadata that users can share, curate, and discover. This NIP defines a standard format for link list events that enables interoperability between different Nostr clients and promotes consistent handling of link-sharing features.

## Motivation

Link sharing and curation are fundamental activities in online communities. While users can share individual links in text notes or save them privately using NIP-51 bookmarks, there's a need for a standardized format specifically designed for public, curated link collections. This NIP enables:

- Public sharing of curated link collections (e.g., "link-in-bio" style lists)
- Better organization and discovery of related resources
- Consistent metadata across implementations
- Support for internationalization
- Improved user experience through specialized UI
- Interoperability between different clients

The distinction from personal bookmarks (NIP-51) is intentional - while bookmarks serve as private reading lists, NIP-74 link lists are designed for public sharing and discovery, enabling users to curate and share collections of resources with their community.

## Event Format

### Kind: 30001

Link list events use kind `30001`.

### Content

The content field MUST be empty. All data is stored in tags.

### Tags

Required tags:
- `ll` ["list"] - Identifies this as a link list event
- `title` [list_title] - Name of the list
- `nl` [url, description, language?, direction?] - One or more link entries
  - `url`: The URL being shared (must follow protocol requirements)
  - `description`: Text description of the link (must be non-empty)
  - `language`: Optional ISO 639-1 language code
  - `direction`: Optional text direction ("ltr" or "rtl")

Optional tags:
- `lang` [code] - Default language for the list (ISO 639-1)
- `dir` [direction] - Default text direction ("ltr" or "rtl")
- `t` [topic] - Topics/hashtags for discovery
- `summary` [text] - Brief description of the list
- `image` [url] - Cover image for the list

### URL Protocol Support

The format supports various URL protocols to accommodate different types of resources:

Standard Web Protocols:
- `http://`, `https://` - Standard web URLs
- `ftp://`, `sftp://` - File transfer protocols

Special Protocols:
- `magnet:` - BitTorrent magnet links
- `ipfs://` - IPFS content
- `nostr:` - Nostr protocol links
- `dat://` - Dat protocol
- `git://` - Git repository links
- `ssh://` - Secure shell links

Extended Protocols:
- `mailto:` - Email addresses
- `tel:` - Phone numbers
- `sms:` - Text message links
- `geo:` - Geographic locations

### URL Validation and Security

1. Protocol Validation:
   - URLs MUST start with one of the supported protocols
   - Custom protocols MAY be supported by clients but MUST be clearly marked
   - Clients SHOULD implement appropriate security measures for each protocol

2. Protocol-Specific Metadata:
   ```json
   {
     "kind": 30001,
     "tags": [
       ["ll", "list"],
       ["title", "Mixed Protocol Resources"],
       ["nl", "https://example.com", "Web Resource"],
       ["nl", "magnet:?xt=urn:btih:...", "Linux ISO Torrent", null, null, "torrent"],
       ["nl", "ipfs://Qm...", "IPFS Document", null, null, "ipfs"],
       ["nl", "nostr:npub1...", "Nostr Profile", null, null, "nostr"]
     ],
     "content": ""
   }
   ```

3. Client Handling:
   - Clients MUST verify protocol support before attempting to open links
   - Clients SHOULD display appropriate icons/indicators for different protocols
   - Clients MAY implement protocol-specific preview features
   - Clients SHOULD warn users when opening non-HTTP protocols

### Examples

1. Basic link list with default language:
```json
{
  "kind": 30001,
  "tags": [
    ["ll", "list"],
    ["title", "Favorite Programming Resources"],
    ["lang", "en"],
    ["dir", "ltr"],
    ["nl", "https://example.com/tutorial", "Great Python Tutorial"],
    ["t", "programming"]
  ],
  "content": ""
}
```

2. Multilingual list with mixed content:
```json
{
  "kind": 30001,
  "tags": [
    ["ll", "list"],
    ["title", "Global Dev Resources"],
    ["lang", "en"],
    ["dir", "ltr"],
    ["nl", "https://example.com/docs", "Documentation"],
    ["nl", "https://arabic-example.com/tutorial", "شرح البرمجة", "ar", "rtl"],
    ["nl", "https://japanese-site.com/guide", "プログラミング入門", "ja"],
    ["t", "programming"],
    ["t", "tutorials"]
  ],
  "content": ""
}
```

## Relationship to Other NIPs

This NIP builds upon and complements several existing NIPs:

1. [NIP-01](01.md) provides the basic protocol structure we build upon
2. [NIP-23](23.md) demonstrates handling of longer-form content
3. [NIP-51](51.md) defines lists, including bookmarks (kind:10003) which are primarily for personal use - saving posts, articles, and URLs for later reading. While NIP-51's bookmarks serve as a private reading list, NIP-74 focuses on public, shareable collections designed for distribution and discovery:
   - Curated collections meant to be shared (like "link-in-bio" lists)
   - Rich metadata for the collection as a whole
   - Consistent theme or purpose across all links
   - Enhanced internationalization support
   - Protocol-specific handling for various link types
   - Collection-level discovery and organization

For example:
- NIP-51 Bookmark: "Save this article to read later" (personal use)
- NIP-74 Link List: "My public collection of resources about Nostr" (sharing with others)

This separation of concerns allows:
- NIP-51 to handle personal, private bookmarking for later reading
- NIP-74 to focus on public, curated collections meant for sharing
- Users to have both private reading lists and public resource collections

## Finding Link Lists

To discover a user's link lists:
1. Filter for events by the user's pubkey
2. Filter for events with kind 30001
3. Filter for events with the tag `["ll", "list"]`

## Client Behavior

### Required Behavior

Clients MUST:
- Include the `["ll", "list"]` tag in all link list events
- Validate URLs to ensure they:
  - Start with http:// or https://
  - Have a non-empty description
  - Support Unicode domains (IDN/Punycode)
- Handle both profile-level and link-level language settings
- Support RTL text rendering when specified

### Recommended Behavior

Clients SHOULD:
- Display link lists in a way that makes their curated nature clear
- Respect language and text direction settings
- Provide ways to discover lists by topic/hashtag
- Support Unicode normalization for non-Latin text
- Handle bidirectional text properly

Clients MAY:
- Fetch link previews (titles, descriptions, images)
- Provide specialized UI for different types of links
- Support list organization features
- Implement list sharing and discovery features

## Implementation Notes

1. Language Support
   - Use ISO 639-1 two-letter codes (e.g., "en", "es", "ar", "ja")
   - Default to profile language if not specified per link
   - Support both LTR and RTL text rendering
   - Handle mixed-language content appropriately

2. URL Handling
   - Validate URLs before displaying
   - Support IDN/Punycode domains
   - Consider implementing preview safety measures

3. Backward Compatibility
   - Default to "en"/"ltr" when language/direction not specified
   - Support legacy formats during transition
   - Handle missing optional tags gracefully

## Extensions

Future extensions might include:
- Link categorization within lists
- Collaborative list editing
- List versioning
- Enhanced metadata for specific link types
- Integration with other NIPs (e.g., reactions, comments)

## References

- [NIP-01: Basic protocol flow description](01.md)
- [NIP-23: Long-form Content](23.md)
- [NIP-51: Lists](51.md)