# Certificate Registry

**Certificate Registries** are smart contracts that allow users to issue ERC-1155/ERC-1888 type of NFTs.\
\
Multiple Issuers can connect to the same Registry and issue NFTs on it.

Only a single Issuer (smart contract or blockchain account) can issue NFTs with a specific [topic](/zerolabs-tokenization-module/domain-definitions/issuer/topics.md).\
\
Each topic can have a separate agreed-upon NFT [metadata](https://app.gitbook.com/s/J1hmZlUO8raciusperMH/~/changes/MQ7T6VtrjPWiHnuzLbWf/domain-definitions/smart-contracts/certificate-registry/issuance-metadata) structure upon issuance.

### Class Diagram

Source code: [https://github.com/zerolabsgreen/tokenization/blob/develop/packages/contracts/contracts/CertificateRegistry.sol](https://github.com/zerolabsgreen/token/blob/develop/packages/contracts/contracts/CertificateRegistry.sol)

![](/files/HVntO7fHFIWpnBaj0i18)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.zerolabs.green/zerolabs-tokenization-module/domain-definitions/smart-contracts/certificate-registry.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.