FIO Crypto Handles & Domains

FIO Crypto Handles

FIO Crypto Handles (aka FIO Addresses) act as the human-readable wallet identifier for users on the FIO Protocol. They are necessary for users to utilize all the capabilities of the FIO Protocol, but also serve as a replacement for complicated public addresses across all tokens and coins in the user’s wallet.

FIO Crypto Handles have the construct of [email protected] Examples of a FIO Crypto Handle include:

[email protected]


[email protected]

Registration of a FIO Crypto Handle is done directly through a FIO-enabled application, or through a hosted registration site that is open to the community.

The FIO Crypto Handle itself and all subsequent interactions with the FIO Protocol are controlled via a FIO private key. Loss of access to this private key suffers the same consequences as with any crypto asset - the FIO Crypto Handle will no longer be usable by the original owner, nor can it be retrieved.

Format of a FIO Crypto Handle

A FIO Crypto Handle consists of a username and a domain delimited by an @ symbol, there are not specific requirements around a FIO Crypto Handle username, but there are format restrictions around the FIO Crypto Handle as a whole, and then separate requirements for a FIO Domain in particular.

  FIO Crypto Handle ([email protected]) FIO Domain
Min. Chars 3 1
Max Chars 64 (including FIO Domain) 62
Characters allowed ASCII a-z 0-9 - (dash) with single @ (at sign) Domains may contain ASCII a-z 0-9 - (dash)

** The dash can not be the first or last character of the crypto handle or domain

FIO Crypto Handle validation using regex

Regex validation may be used. For example, the following regex may be used to validate a FIO Crypto Handle:


Mapping a FIO Crypto Handle to crypto public addresses

See Mapping Public Addresses in the Integration Guide.

FIO Crypto Handles Do Not Expire

After FIP-31 was implemented, FIO Crypto Handles no longer expire and are only burned if the FIO Domain they are on expires.

FIO Domains

FIO Crypto Handles consist of a username and a domain. While having a FIO Crypto Handle is necessary to use the FIO Protocol, users do not need to own their own FIO Domain. By default, many applications (especially wallets and exchanges) have a domain available as a default for their users. For example, the mobile wallet, Edge Wallet, has @edge domain as a default for their users. Users which desire their own unique FIO domain may register one that is available as a non-fungible token that they control and own.

Outside of centralized services (which own all user private keys, including FIO Crypto Handles), users are not obligated to use a specific domain for their FIO Crypto Handle, regardless of the wallet they choose to use.

Domain Owner Abilities

A domain owner has several unique actions that are specific towards their management of a domain and any subsequent registrations of FIO Crypto Handles.

  • Public/Private Flag - by default, a FIO Domain can only be used for a FIO Crypto Handle registration from the domain owner themselves. If chosen, the domain owner can change their domain to public, which would allow anyone with a FIO private key to register a FIO Crypto Handle on their domain. This functionality is inherent to the mechanics of the FIO Protocol, though whether a particular wallet provides that option through their UI may differ.

Importantly - a domain owner is NOT able to control FIO Crypto Handles on their domain, decrypt any data associated with transactions made by any registered FIO Crypto Handles on their domain, nor are they able to change the fee structure of FIO Crypto Handle registration/renewal as that is dictated by the block producers (this is separate from running a registration site, which allows for various other economic choices).

For a list of public domains see the FIO Grafana Public Domains report.

Storing, Transferring, and Selling FIO Domains

All FIO Domains are non-fungible tokens, which means they can be freely transferred between accounts, users, and wallets as with any other crypto asset.

Future functionality will enable selling a FIO Domain through the use of a built-in escrow smart contract, in which both the domain owner and the buyer deposits their respective NFT and payment before transfer of the domain to the new owner is executed.

FIO Domains and Decentralized Domain Efforts

A number of projects are underway with the goal of creating a decentralized domain name space system for the World Wide Web. Should any of those projects become recognized in the community as the primary decentralized domain space, then the Foundation’s vision is that the FIO Protocol will hopefully endeavor to work collaboratively with them, though such a decision will be up to the protocol Block Producers. Specifically, FIO domains do not currently have the concept of a Top Level Domain (e.g., .com, .org, .net, .io) but such a construct could be added in the future to the notion of a FIO Crypto Handle and a unique TLD for FIO Crypto Handles registered for the FIO Protocol enabling FIO Crypto Handles to work seamlessly with a decentralized domain name space.

FIO Domain Expiry

If the renewal fee for a FIO Domain is not paid by its expiration date, the following restrictions will be placed on the domain and addresses on that domain:

Note: FIO Crypto Handles are referred to as “fio_address” in the calls.

Days after expiration date Domain actions disallowed Address actions disallowed
0 - 30 setdomainpub
31 - 90 setdomainpub
newfundsreq (Payee FIO Crypto Handle only)
rejectfndreq (Payer FIO Crypto Handle only)
recordobt (Payer FIO Crypto Handle only)
On day 90 Domain is burned and can be re-registered by any user. All addresses on that domain and associated data are burned.

It’s important to note that anyone can renew a domain as long as they are willing to pay the renewal fee. This ensures that users with FIO Crypto Handles on abandoned domain, can continue to use it.

Domain Renewal

You can view complete instructions including screenshots for how to renew your FIO Domain with Edge Wallet, the FIO Registration Helper, the Block Explorer, or the API directly here: How to Renew Your FIO Crypto Handle or FIO Domain.