eranos/NIP.md

NIP: Custom Event Kinds

Event Kinds Overview

Kind	Name	Description
36767	Theme Definition	Shareable, named custom UI theme
16767	Active Profile Theme	The user's currently active theme (one per user)
16769	Profile Tabs	The user's custom profile page tabs (one per user)
8211	Encrypted Letter	Encrypted personal letter with visual stationery

---

Kind 36767: Theme Definition

Summary

Addressable event kind for publishing shareable custom UI themes. A single user may publish multiple themes, each identified by a unique d tag.

A theme consists of colors, optional fonts, and an optional background. Colors are stored in c tags, fonts in f tags, and background in a bg tag.

Event Structure

{
  "kind": 36767,
  "content": "",
  "tags": [
    ["d", "mk-dark-theme"],
    ["c", "#1a1a2e", "background"],
    ["c", "#e0e0e0", "text"],
    ["c", "#6c3ce0", "primary"],
    ["f", "Inter", "https://example.com/inter.woff2", "body"],
    ["f", "Playfair Display", "https://example.com/playfair.woff2", "title"],
    ["bg", "url https://example.com/bg.jpg", "mode cover", "m image/jpeg", "dim 1920x1080"],
    ["title", "MK Dark Theme"],
    ["alt", "Custom theme: MK Dark Theme"]
  ]
}

Content

The content field is unused and MUST be an empty string ("").

Tags

Tag	Required	Description
d	Yes	Unique identifier (slug) for this theme, e.g. "mk-dark-theme"
c	Yes (×3)	Hex color with marker. See Color Tags.
f	No	Font declaration. See Font Tag.
bg	No	Background media. See Background Tag.
title	Yes	Human-readable theme name
alt	Yes	NIP-31 human-readable fallback

Multiple Themes Per User

Since kind 36767 is addressable, a user can publish multiple themes by using different d tag values. Publishing a new event with the same d tag replaces the previous version (this is how editing works).

---

Kind 16767: Active Profile Theme

Summary

Replaceable event that represents the user's currently active profile theme. Only one per user. When other users visit a profile, they query this kind to determine what theme to display.

Event Structure

{
  "kind": 16767,
  "content": "",
  "tags": [
    ["c", "#1a1a2e", "background"],
    ["c", "#e0e0e0", "text"],
    ["c", "#6c3ce0", "primary"],
    ["f", "Inter", "https://example.com/inter.woff2", "body"],
    ["f", "Playfair Display", "https://example.com/playfair.woff2", "title"],
    ["bg", "url https://example.com/bg.jpg", "mode cover", "m image/jpeg"],
    ["title", "MK Dark Theme"],
    ["alt", "Active profile theme"]
  ]
}

Content

The content field is unused and MUST be an empty string ("").

Tags

Tag	Required	Description
c	Yes (×3)	Hex color with marker. See Color Tags.
f	No	Font declaration. See Font Tag.
bg	No	Background media. See Background Tag.
title	No	Human-readable name for the theme
alt	Yes	NIP-31 human-readable fallback

Client Behavior

• When visiting a profile, clients query { kinds: [16767], authors: [pubkey], limit: 1 } to get the active theme.
• Clients read the c tags to extract colors, f tags for fonts, and bg tag for the background.
• Setting a new active theme publishes a new kind 16767 event (replacing the old one).
• To remove the active theme, publish a kind 5 deletion event targeting kind 16767.

---

Shared Tag Definitions

The following tag definitions apply to both kind 36767 and kind 16767.

Color Tags

Format: ["c", "#rrggbb", "<marker>"]

Index	Required	Description
0	Yes	Tag name: "c"
1	Yes	Lowercase 6-digit hex color code including the # sign (e.g. "#ff0000")
2	Yes	Color role marker: one of "primary", "text", or "background"

• All three markers ("primary", "text", "background") MUST be present.
• Only one c tag per marker is allowed.

Font Tag

Format: ["f", "<family>", "<url>", "<role>"]

Index	Required	Description
0	Yes	Tag name: "f"
1	Yes	CSS font-family name (e.g. "Inter")
2	Yes	Direct URL to a font file (.woff2, .ttf, .otf)
3	Yes	Font role: "body" or "title"

Roles:

Role	Applies to
"body"	All text globally (body, headings, UI elements)
"title"	The user's profile display name

Rules:

• The f tag is optional on the event.
• At most one f tag per role is allowed (i.e. one body font and one title font).
• The "body" font tag MUST be ordered before the "title" font tag. This ensures backward-compatible clients that only read the first f tag will pick up the body font.
• If the URL fails to load, the client SHOULD fall back to a default font gracefully.
• Clients that do not recognize a role SHOULD ignore that f tag.
• Legacy events with an f tag that has no role marker (only 3 elements) SHOULD be treated as "body".
• Variable font files (covering multiple weights in a single file) are preferred.

Background Tag

The bg tag uses an imeta-style variadic format where each entry (after the tag name) is a space-delimited key/value pair.

Format: ["bg", "url <url>", "mode <mode>", "m <mime-type>", ...]

Key	Required	Description
url	Yes	URL to an image or video file
mode	Yes	Display mode: "cover" or "tile"
m	Yes	MIME type (e.g. "image/jpeg", "image/png", "video/mp4")
dim	No	Dimensions in pixels: "<width>x<height>" (e.g. "1920x1080")
blurhash	No	Blurhash placeholder string for progressive loading

• At most one bg tag is allowed per event.
• Clients MAY choose not to render video backgrounds for performance or bandwidth reasons.
• Unknown keys SHOULD be ignored for forward compatibility.

---

Kind 16769: Profile Tabs

Summary

Replaceable event kind for publishing a user's custom profile page tabs. Exactly one event per user (no d tag). Each tab defines a Nostr filter (NIP-01) that clients execute to populate the tab's content.

Visitors who load a profile fetch this event to display the custom tabs alongside the standard Posts / Media / Likes / Wall tabs.

Event Structure

{
  "kind": 16769,
  "content": "",
  "tags": [
    ["var", "$follows", "p", "a:3:$me:"],
    ["tab", "Bitcoin Posts", "{\"kinds\":[1],\"authors\":[\"$me\"],\"search\":\"bitcoin\"}"],
    ["tab", "Feed", "{\"kinds\":[1,6],\"authors\":[\"$follows\"],\"limit\":40}"],
    ["alt", "Custom profile tabs"]
  ]
}

Content

The content field is unused and MUST be an empty string ("").

Tags

Tag	Format	Description
tab	["tab", "<label>", "<filterJSON>"]	One tag per custom tab. Order defines display order.
var	["var", "<$name>", "<tag>", "<pointer>"]	Variable definition. See Variable Tags.
alt	["alt", "Custom profile tabs"]	NIP-31 human-readable fallback. Required.

Tab Filter JSON

The third element of each tab tag is a JSON-encoded NIP-01 filter object, optionally extended with the NIP-50 search field. Variable placeholders (strings starting with $) may appear wherever a string value is expected.

{
  "kinds": [1],
  "authors": ["$me"],
  "search": "bitcoin",
  "limit": 20
}

Supported filter fields: ids, authors, kinds, #<tag> (e.g. #t, #e, #p), since, until, limit, search.

Variable Tags

Variable tags define named placeholders that are resolved before the filter is executed. Each var tag extracts tag values from a referenced Nostr event.

Format: ["var", "$name", "<tag-to-extract>", "<event-pointer>"]

Index	Description
0	Tag name: "var"
1	Variable name, starting with $ (e.g. "$follows")
2	Tag name to extract values from in the referenced event (e.g. "p")
3	Event pointer: e:<event-id> for a specific event, or a:<kind>:<pubkey>:<d-tag> for an addressable/replaceable event coordinate. Variables like $me may appear in the pubkey position.

Example — extract follow list pubkeys:

["var", "$follows", "p", "a:3:$me:"]

This means: fetch the kind 3 event authored by $me, extract all p tag values, and bind them to $follows.

Reserved Variable: $me

The $me variable is the only runtime-provided variable. It resolves to the profile owner's pubkey (the author of the kind 16769 event). It does not require a var tag definition.

Variable Resolution

When a variable appears in a filter field that expects an array (e.g. authors, ids, #p), the variable is expanded in-place (spliced into the array). Literal values may be mixed with variables.

["tab", "Mixed", "{\"authors\":[\"$follows\",\"abc123...\"],\"kinds\":[1]}"]

After resolution (assuming $follows = ["pk1", "pk2"]):

{"authors": ["pk1", "pk2", "abc123..."], "kinds": [1]}

Behavior

• To add or update tabs: publish a new kind 16769 event with all current tab and var tags.
• To clear all tabs: publish a kind 16769 event with no tab tags (only alt).
• Clients MUST filter by authors: [pubkey] when querying to prevent spoofing.
• var tags are shared across all tab tags in the same event.

---

Kind 0 Extension: Avatar Shape

Summary

An optional shape property on kind 0 (profile metadata) that controls how the user's avatar is masked/clipped when displayed. The value is an emoji character whose silhouette is used as a mask over the avatar image. When absent, the avatar renders as the standard circle.

Metadata Field

The shape field is added to the JSON content of a kind 0 event alongside standard fields like name, picture, etc. Its value is a single emoji character (including multi-codepoint emoji such as flags, ZWJ sequences, and skin-tone variants).

{
  "kind": 0,
  "content": "{\"name\":\"Luna\",\"picture\":\"https://example.com/luna.jpg\",\"shape\":\"🌙\"}"
}

Client Behavior

• When shape is absent, clients SHOULD render the avatar as a circle (the current universal default).
• When shape is a valid emoji, clients SHOULD use the emoji's silhouette as an alpha mask over the avatar image. The specific rendering technique is platform-dependent (see below).
• When shape is set to an unrecognized or invalid value, clients MUST fall back to a circle. This ensures forward compatibility.
• The shape field is purely cosmetic and has no protocol-level significance.
• Clients MAY choose not to support this extension, in which case avatars render as circles as usual.