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NIP-A0

Voice Messages

DraftEvents

Short voice notes of up to about a minute: kind 1222 for a new message and kind 1244 for a voice reply, each pointing to an audio file.

Status
In use and still allowed to change.
Kinds
Last changed
Jul 27, 2025

Try it

Edit the form or the JSON: both stay in sync, the badge says whether the result is valid, and tapping any field explains it.

What to build

How the parts connect: A voice conversation

Examples
Valid 1 note

Not signed yet · Demo keys only. These personas' secret keys are public on purpose.

Form
Jan 1, 2025, 12:00 AM UTC

Content

Exactly one URL that points directly at the audio file.

Tags

  1. imeta Optional

    NIP-92 media metadata for a URL in the content: one tag per URL, each value a 'key value' pair.

  2. t Optional

    A hashtag, as in any other note.

Add tag

How this NIP works

Step 1 of 4

Record and upload

The app records a short clip, uploads it (for example to a Blossom server) and puts the file's URL in the content. The content is only the URL, nothing else.

In the course

No course chapter covers this NIP yet. The editor above is the quickest way in.

Builds on

See also

Specification

Specification text is quoted in English from the nostr-protocol/nips repository. Our explanations and the interface are translated. Source on GitHub at commit 0046368

Read the spec466 words, quoted from the repository at commit 0046368.

This NIP defines new events kind: 1222 for root messages and kind: 1244 for reply messages to be used for short voice messages, typically up to 60 seconds in length.

Specification

Event Kind 1222 and Kind 1244

The kind: 1222 event is defined as follows:

  • content: MUST be a URL pointing directly to an audio file.
    • The audio file SHOULD be in audio/mp4 (.m4a) format using AAC or Opus encoding. Clients MAY support other common audio formats like audio/ogg, audio/webm, or audio/mpeg (mp3), but audio/mp4 is recommended for broad compatibility and efficiency.
    • The audio duration SHOULD be no longer than 60 seconds. Clients publishing kind: 1222 events SHOULD enforce this limit or provide a clear warning to the user if exceeded.
  • tags:
    • Tags MAY be included as per other NIPs (e.g., t for hashtags, g for geohash, etc.).

The kind: 1244 event is defined as follows:

  • To be used for replies, kind: 1244 events MUST follow the structure of NIP-22.
  • content: MUST be a URL pointing directly to an audio file.
    • The audio file SHOULD be in audio/mp4 (.m4a) format using AAC or Opus encoding. Clients MAY support other common audio formats like audio/ogg, audio/webm, or audio/mpeg (mp3), but audio/mp4 is recommended for broad compatibility and efficiency.
    • The audio duration SHOULD be no longer than 60 seconds. Clients publishing kind: 1222 events SHOULD enforce this limit or provide a clear warning to the user if exceeded.
  • tags:
    • Tags MAY be included as per other NIPs (e.g., t for hashtags, g for geohash, etc.).

Visual representation with imeta (NIP-92) tag (optional)

The following imeta (NIP-92) tags MAY be included so clients can render a visual preview without having to download the audio file first:

  • waveform: amplitude values over time, space separated full integers, less than 100 values should be enough to render a nice visual
  • duration: audio length in seconds

Examples

Root Voice Message Example

{
  "content": "https://blossom.primal.net/5fe7df0e46ee6b14b5a8b8b92939e84e3ca5e3950eb630299742325d5ed9891b.mp4",
  "created_at": 1752501052,
  "id": "...",
  "kind": 1222,
  "pubkey": "...",
  "sig": "...",
  "tags": [
    [
      "imeta",
      "url https://blossom.primal.net/5fe7df0e46ee6b14b5a8b8b92939e84e3ca5e3950eb630299742325d5ed9891b.mp4",
      "waveform 0 7 35 8 100 100 49 8 4 16 8 10 7 2 20 10 100 100 100 100 100 100 15 100 100 100 25 60 5 4 3 1 0 100 100 15 100 29 88 0 33 11 39 100 100 19 4 100 42 35 5 0 1 5 0 0 11 38 100 94 17 11 44 58 5 100 100 100 55 14 72 100 100 57 6 1 14 2 16 100 100 40 16 100 100 6 32 14 13 41 36 16 14 6 3 0 1 2 1 6 0",
      "duration 8"
    ]
  ]
}