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CTMeta Standard


CKB Transaction Metadata (aka. CTMeta) is the standard of additional metadata for transactions, tokens, and smart contracts on Nervos CKB. It dramatically reduces CKB state cost by using witness as the static data storage space. The typical user scenarios of CTMeta include transaction postscript, token definition, NFT description, and so on.


The convention

CTMeta uses group_witnesses[0].output_type as the data container. The data should be written in Json format, with the following schema.

"id": "CTMeta", // identifier for off-chain processor
"ver": "1.0", // current version
"target": "output#0", // description for which utxo, format: {input, output}#index
"type": "nft-renderer", // metadata types
"data": <payload_data> // detail metadata for various types
"target": "output#1", // an example for transfer postscript
"type": "postscript",
"data": "I love you."
// ...

Pre-defined metadata type

schema typedescriptionschema standard
cota.nft.define*CoTA NFT definitionCoTA NFT Metadata Schema
cota.ft.defineCoTA FT definitionCoTA Fungible Token Metadata Schema
issuercota token issuer informationWIP
postscriptgeneral transfer postscript for ckb/sudt/nftUTF-8 encoded
sudt-infosudt definitionWIP

* In previous design, the CoTA NFT definition schema type is cota. To keep compatibility, cota.nft.define and cota will both valid.