Properties

Inscriptions may include CBOR properties, stored as data pushes in fields with tag 17. Since data pushes are limited to 520 bytes, CBOR longer than 520 bytes must be split into multiple tag 17 fields which are then concatenated before decoding.

Properties are a structured counterpart to metadata. While metadata may contain arbitrary CBOR which has no protocol-defined meaning, and is presented on /inscription as free-form HTML, properties have protocol-defined meaning and must conform to a strict schema.

Indefinite-length CBOR types are not supported in properties. All maps, arrays, byte strings, and text strings must be definite.

The non-normative CDDL schema of the properties value is as follows:

Properties = {
  ? 0: [*Item],
  ? 1: Attributes,
  * any => any,
}

Item = {
  ? 0: bytes .size (32..36),
  ? 1: Attributes,
  * any => any,
}

Attributes = {
  ? 0: text,   ; title
  ? 1: Traits, ; traits
  * any => any,
}

Traits = {
  ; trait names must be unique
  text => Trait,
}

Trait = bool / int / null / text;

The above CDDL schema is provided as a convenience. As always, the ordinals reference implementation ord is the normative specification of inscriptions, and thus the properties field.

Fields matching the * any => any wildcard must be accepted but ignored, for compatibility with future additions.

Compression

If the inscription property encoding field, tag 19, is set to "br", the value of the properties field will be decompressed with Brotli.

Inscription properties my be compressed when inscribing with ord wallet inscribe and ord wallet batch with the --compress flag.

To avoid decompression bombs, the maximum size of decompressed properties is 4,000,000 bytes.

To avoid denial-of-service attacks, the maximum compression ratio of decompressed properties is 10:1. So, for example, if the compressed properties are 100 bytes, the maximum size of the decompressed properties is 1,000 bytes.

Inscriptions with any of the below issues are treated by ord as if they have no properties:

• properties encoding field set to a value other than "br"
• properties which decompress to over 4,000,000 bytes
• properties with a compression ratio greater than 10:1

Galleries

Inscriptions whose properties field contains Items are galleries.

Galleries contain Items, whose key 0 contains a serialized inscription ID. Inscription ID TXIDiINDEX is serialized as a byte string containing the 32 byte TXID, concatenated with by the four-byte little-endian INDEX. Trailing zeros may be removed from four-byte INDEX, so IDs ending in i0 may be serialized in 32 bytes.

Gallery items are displayed on the inscriptions /inscription page on the explorer.

Galleries are similar to children, in that they provide a way to create collections of inscriptions. However, galleries are permissionless. Anyone may create a gallery including any inscriptions. Thus, inclusion in a gallery does not imply provenance. Additionally, because of this, inclusion in a gallery does not create a backlink from the gallery item's /inscription page to the gallery.

Galleries may be created when batch inscribing with ord wallet batch by including an array of string inscription IDs of under the gallery key of the inscription entry in the batch file, or when using ord wallet inscribe using the --gallery option.

Attributes

Attributes are structured metadata that may be attached to both inscriptions and gallery items.

Traits

Traits are a structured counterpart to metadata. While metadata may be arbitrary CBOR, traits are ordered maps of string names to values. Names must be unique, and values may be booleans, integers, null, or strings.