I want to sell / rent out subnames!

Say you own the wrapped name verypopularname.eth. Obviously you can just manually create wrapped subnames like my.verypopularname.eth and then sell them on an NFT marketplace. But that sure doesn't scale well.

To accomplish this, you will want to create a subname registrar. This is a contract that will handle all the registration / renewal for you, and then users will be able to interact with that contract in order to register their own subnames.

In fact, this is exactly how .eth 2LDs are registered. The owner of the eth TLD (the NFT contract) delegates registration / renewal to the ETHRegistrarController contract. It is acting as a subname registrar for the name eth.

Your contract would expose a register method that anyone can call. Under the hood it will use the setSubnodeOwner or setSubnodeRecord methods to create subnames, passing in the fuses and expiry you want to set.

First, note that if you want to burn any fuses on subnames, then your name must be Locked (meaning CANNOT_UNWRAP is burned).

Assuming that you want your subnames to be "unruggable", such that you cannot replace / revoke them, then you will want to burn PARENT_CANNOT_CONTROL on the subnames. This will place them in the Emancipated state upon registration.

If you want to sell "forever" subnames, where users register once and can then keep them for as long as they wish, then you can consider burning the CAN_EXTEND_EXPIRY fuse.

This will allow the subname owner to extend their own expiry whenever they want. The max expiry is the expiry of the parent name, but the .eth Registrar allows anyoneto renew/extend a .eth 2LD as well.

If you just want to rent subnames, then do not burn CAN_EXTEND_EXPIRY. Instead, you could include a renewmethod on your contract that users can call for another fee.

If you want to enable "unruggable renewals" for your registrar, to guarantee that users will always be able to renew, then you can call approve on the Name Wrapper and approve your registrar contract as the "subname renewal manager" for your name.

Then, burn the CANNOT_APPROVE fuse on your name, to guarantee that you can never revoke that contract for subname renewals. See the Approved Operators section above for more info.

If you want to impose other restrictions on your registered subnames, then you can burn the CANNOT_UNWRAPfuse to Lock the subname, and also burn whatever other fuses you want.

For example, if you want to prevent owners of your subnames (like my.verypopularname.eth from creating their own subnames (like buy.my.verypopularname.eth), then you would burn CANNOT_UNWRAP and CANNOT_CREATE_SUBDOMAIN.

To recap on fuses…

And so on, it's up to you. You can also burn whatever custom parent-controlled or owner-controlled fuses you want to.

Yes! It's your registrar contract, so you can impose whatever rules and fees you want.

For example, the .eth Registrar imposes a 3-character minimum on all names, as well as a custom fee structure and a temporary premium auction upon expiration.

By default there is no character limit on subnames, but your contract could have its own rules and fee structure or whatever you want. For example, you can: