> For the complete documentation index, see [llms.txt](https://nexanetwork.gitbook.io/nexa/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://nexanetwork.gitbook.io/nexa/technical-architecture/new-and-existing-tokens.md).

# New & Existing Tokens

## Implementation Types

The **Chain-Agnostic Token** standard has two implementations when being transferred from one chain to another. 

* **New tokens:** Burn & Mint
* **Existing tokens:** Lock & Mint

With both implementations, no tokens are escrowed in third-party bridging contracts. 

<table><thead><tr><th width="118.33333333333331"></th><th width="248">Token Types</th><th>Description</th></tr></thead><tbody><tr><td>Burn &#x26; Mint</td><td><ul><li>New tokens (ERC20)</li><li>New NFTs (ERC721)</li></ul><p><em>Not yet deployed on any chains</em> </p></td><td>Each time tokens are transferred from one chain to another, it will <strong>burn</strong> the amount on the origin chain, and <strong>mint</strong> the amount on the destination chain. </td></tr><tr><td>Lock &#x26; Mint </td><td><ul><li>Existing tokens (ERC20)</li><li>Existing NFTs (ERC721)</li></ul><p><em>Currently deployed on one chain</em></p></td><td>When tokens are transferred from the Home Chain to Chain B, it will <strong>lock</strong> the amount on Home Chain, and <strong>mint</strong> the amount on Chain B. <br><br>When tokens are transferred from Chain B to A, it will <strong>burn</strong> the amount of Chain B, and <strong>unlock</strong> the amount on Home Chain.  <br><br>This approach is necessary for existing token contracts since the original token cannot be modified to support re-minting. Instead, a 'lock' is created in a proxy contract owned by the token issuer. Chain-Agnostic Tokens are not held in third-party bridging contracts, ensuring that there is no risk to the funds in case vulnerabilities exist in bridges.</td></tr></tbody></table>

With both implementations, additional chains can be added at any stage.&#x20;