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ioTube - the decentralized bridge for Ethereum, Binance Smart Chain, Polygon(Matic) and IoTeX

Version history

V1.0 IOTX tube

Launch date: Apr 2019 (Announcement)

The first version of ioTube was built by core-dev in Apr. 2019 to facilitate the swap of IOTX-E (ERC20 version of IOTX on Ethereum) and IOTX mainnet token.

V2.0 Multi Token Tube (IoTeX <-> Ethereum)

Launch date: Aug 31, 2020 (Announcement)

V2 generalizes the ioTube V1 to support multiple assets on Ethereum & IoTeX blockchains.

V3.0 Rebuilt with largely fee reduction

Launch date: Feb 8, 2021 (Announcement)

Ethereum has been suffering high gas cost for a long period. The core-dev team rebuilt ioTube to largely reduced the gas cost on ETH side by introducing a relayer and putting signature offchain.

V4.0 Multi-Chain support

Launch date: Apr 13, 2021 (Annoucement)

Because of Ethereum's high gas cost, many projects and users also adopted Binance Smart Chain (BSC) and Huobi Eco Chain (Heco). The need of supporting BSC and Heco is increasing. The demand of cross-chain support from Ethereum and BSC or other blockchains are increasing. We'd love to support them in ioTube.

Matic support is launched on Jun 10, 2021 (Annoucement)

V5.0 Web3 (Babel) Support + Transactions + More Assets + Crosschain Tokens

Beta is open to public:

Any bug report or feedback? Please submit an issue or discuss in

Deployement | Usage | Documentation


Submit a token to ioTube?

Please refer to token submission guide first:

Feel free to reach out to for further discussion.


Different from traditional bridges, ioTube comes with two components:

  • a golang service witnessing what has happened on both changes and relay the finalized information
  • a set of smart contracts pre-deployed on both chains letting the legitimate witnesses relay information back and forth to facilitate cross-chain transferring of assets

Deploy Contracts on IoTeX/Ethereum

  • Deploy a TokenSafe ts
  • Deploy a TokenList tl1, which stores tokens using ts
  • Deploy a MinterPool mp
  • Deploy a TokenList tl2, which stores tokens using mp
  • Deploy a WitnessList wl
  • Deploy a TokenCashier tc with ts, tl1, and tl2
  • Deploy a TransferValidator tv with ts, mp, tl1, tl2, and wl
  • Transfer ownership of mp to tv
  • Transfer ownership of ts to tv
  • Add witnesses to wl
  • Add tokens to tl1 or tl2

Join as a Relayer

  1. Edit witness-service/relayer-config-iotex.yaml and witness-service/relayer-config-ethereum.yaml to fill in the following fields:
  • privateKey
  • clientURL
  • validatorContractAddress
  1. start containers
cd witness-service

Join as a Witness

  1. Edit witness-service/witness-config-iotex.yaml and witness-service/witness-config-ethereum.yaml to fill in the following fields:
  • privateKey
  • clientURL
  • validatorContractAddress
  • cashierContractAddress
  1. start containers
cd witness-service
  1. Clean up everything by running

Transfer assets between IoTeX and Ethereum

Please use dApp ioTube Please note that the service is still in beta mode.

From ERC20 to XRC20

  1. open in a metamask installed browser. (eg. Firefox/Chrome/Brave + metamask)
  2. Choose supported ERC20 token from the list.
  3. Enter the amount.
  4. Click Approve button to approve ERC20 token transfer and sign on metamask.
  5. Click Convert button and sign on metamask.
  6. After 12 confirmations of Ethereum network and 2/3 + 1 confirmations from witnesses, the XRC20 tokens will be minted and sent to your IoTeX address.
  7. You can add the token to your ioPay to see and use them.

From XRC20 to ERC20

  1. open in ioPay desktop supported broswers (eg. Chrome/Firefox/Brave with ioPay desktop installed) or ioPay Android/iOS.
  2. Choose supported XRC20 token from the list.
  3. Enter the amount.
  4. Click Approve button to approve XRC20 token transfer and sign on ioPay.
  5. Click Convert button and sign on ioPay.
  6. After 1 confirmation of IoTeX network and 2/3 + 1 confirmations from witnesses, the XRC20 token will be burnt and ERC20 token will be sent to your ETH wallet.


Tube fees: 0

Network fees:

  1. from ERC20 to XRC20: 0
  2. from XRC20 to ERC20: 2000 IOTX (to cover the high ETH gas fee for witnesses)

Add an ERC20 token to ioTube

  • Add this token to tl on Ethereum
  • Deploy a ShadowToken and add it to tl on IoTeX


  • Each witness needs to be registered to WitnessList contract on both chains based on PoA (Proof-of-Authority).
  • Each transferring of assets from one chain to another needs the endorsement from more than 2/3 of the registered witnesses; otherwise, it will not be successful.
  • IoTeX has instant finality, meaning, to a witness, one confirmed block indicates finalization of a burn event, while on the Ethereum side, a witness needs to wai 12 blocks before making any endorsement.
  • To launch ioTube reliably, we have limited the min/max of the asset that can be moved around. These limits can be lifted once ioTube gets more stress validated.

Gas Costs

Gas fees on IoTeX are negligible, both for bridge maintenance and for asset transfer. The estimated gas fees on Ethereum side are:

  • To transfer token from Ethereum to IoTeX: ~43,952 gas to set allowance and ~151,122 to lock it;
  • To transfer token back from IoTeX to ETH: ~422,525 gas to unlock the token.

Tube of IoTeX <-> Ethereum

Contracts on IoTeX

  • Wrapped IOTX: io15qr5fzpxsnp7garl4m7k355rafzqn8grrm0grz
  • Token Safe: io1cj3f498390srqv765nnvaxuk0rpxyadzpfjz75
  • Minter Pool: io1g7va274ltufv5nh4xawfmt0clel6tfz58p7n5r
  • Standard Token List: io1t89whrwyfr0supctsqcx9n7ex5dd8yusfqhyfz
  • Proxy Token List: io1dn8nqk3pmmll990xz6a94fpradtrljxmmx5p8j
  • Witness List: io1hezp6d7y3246c5gklnnkh0z95qfld4zdsphhsw
  • Token Cashier: io1gsr52ahqzklaf7flqar8r0269f2utkw9349qg8
  • Transfer Validator: io10xr64as4krm5nufd5l2ddc43al6tl0smumkg7y io1dwaxh2ml4fd2wg8cg35vhfsgdcyzrczffp3vus

Contacts on Ethereum

  • WETH: 0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2
  • Standard Token List: 0x7c0bef36e1b1cbeb1f1a5541300786a7b608aede
  • Proxy Token List: 0x73ffdfc98983ad59fb441fc5fe855c1589e35b3e
  • Witness List: 0x8598dF1Ec0ac7dfBa802f4bDD93A6B93bd0AD83f
  • Token Safe: 0xc2e0f31d739cb3153ba5760a203b3bd7c27f0d7a
  • Minter Pool: 0x964f4f19bc823e72cc1f806021937cfc06f63b45
  • Token Cashier: 0xa0fd7430852361931b23a31f84374ba3314e1682
  • Transfer Validator: 0xd8165188ccc135b3a3b2a5d2bc3af9d94753d955

Tube of IoTeX <-> BSC (Binance Smart Chain)

IoTeX Side

  • Validator: io10xr64as4krm5nufd5l2ddc43al6tl0smumkg7y (same for all)
  • Standard Token list: io1h2d3r0d20t58sv6h707ppc959kvs8wjsurrtnk
  • Proxy Token list: io17r9ehjstwj4gfqzwpm08fjnd606h04h2m6r92f
  • Token Cashier: io1zjlng7je02kxyvjq4eavswp6uxvfvcnh2a0a3d

BSC Side

  • Witness List Address: 0x8119411F5A78F73784A1B87dE43d452DA4A1EE3F
  • Minter Pool Address: 0xf72CFb704d49aC7BB7FFa420AE5f084C671A29be
  • Token Safe Address: 0xFBe9A4138AFDF1fA639a8c2818a0C4513fc4CE4B
  • Mintable Token List Address: 0xa6ae9312D0AA3CC74d969Fcd4806d7729A321EE3
  • Standard Token List Address: 0x0d793F4D4287265B9bdA86b7a4083193E8743b34
  • Token Cashier Address: 0x797f1465796fd89ea7135e76dbc7cdb136bba1ca 0x082020Ae0B38fD1bef48895c6cFf4428e420F400
  • Transfer Validator Address: 0x116404F86e97846110EA08cd52fC2882d4AD3123

Tube of IoTeX <-> Heco (Huobi Eco Chain)

Please note this is still being added. They are not in production use yet. Please contact us if you want to use them without interfaces.

IoTeX Side:

  • Validator: io10xr64as4krm5nufd5l2ddc43al6tl0smumkg7y (same for all)
  • Standard Token list: io1kh0vgtxyamdkzvrlvga3r8l7r2plm7phd9ywv9
  • Proxy Token list: io18uqxuel6d93hluua4d9jxs8rjw3r2qe5g3adgk
  • Token Cashier: io1s6m6j3cdj0j7hlgupx0pww7wscvkepdjfwgkra

Heco Side:

  • Witness List Address: 0x2f1a0BCa4005eBfD6A589850F436c8D8f9c2aEd2
  • Minter Pool Address: 0xd2165D222B3dAF2528Fc1b1Aa2DB18B8821EE623
  • Token Safe Address: 0x1E58cA53d90fe9B37F7f6AEB548b4BC7c6292C17
  • Mintable Token List Address: 0x12af43ef94B05A0a3447A05eEE629C7D88A30a5f
  • Standard Token List Address: 0xA239F03Cda98A7d2AaAA51e7bF408e5d73399e45
  • Token Cashier Address: 0xC8DC8dCDFd94f9Cb953f379a7aD8Da5fdC303F3E
  • Transfer Validator Address: 0xDe9395d2f4940aA501f9a27B98592589D14Bb0f7

Tube of IoTeX <-> Polygon (formerly Matic)

Launched on Jun 10, 2021.

We started adding 0x address to this doc because of IoTeX start supporting 0x address and web3 from IoTeX V1.2 (Babel API). Some IoTeX address are same as other tubes and we include 0x addresses here.

IoTeX side:

  • Validator: io10xr64as4krm5nufd5l2ddc43al6tl0smumkg7y
    • (0x7987aaf615b0f749f12da7d4d6e2b1eff4bfbe1b)
  • Standard Token list: io197rk3nff9622pkncvuvhfwyms73esdtwph4rlq
    • (0x2F8768cD292E94A0Da78671974B89B87a398356E)
  • Proxy Token list: io16at6mlcwcsrqutz2zhuhwam87h988r9fcdauk8
    • (0xD757adFF0eC4060e2c4A15f9777767f5Ca738Ca9)
  • Token Cashier:
    • io12s9f9hv4zsr7umy5hxt6g0k0xr4x6pxdp5w998
    • (0x540a92dd951407ee6c94b997a43ecf30ea6d04cd)
  • Token safe: from old.
    • (0xc4A29a94f12be03033daa4e6Ce9b9678c26275a2)
  • Minter pool (old); io1g7va274ltufv5nh4xawfmt0clel6tfz58p7n5r
    • (0x4799d57abf5f12ca4ef5375c9dadf8fe7fa5a454)

Matic side:

  • Witness List Address: 0x1E58cA53d90fe9B37F7f6AEB548b4BC7c6292C17
  • Minter Pool Address: 0x12af43ef94B05A0a3447A05eEE629C7D88A30a5f
  • Token Safe Address: 0xA239F03Cda98A7d2AaAA51e7bF408e5d73399e45
  • Mintable Token List Address: 0xC8DC8dCDFd94f9Cb953f379a7aD8Da5fdC303F3E
  • Standard Token List Address: 0xDe9395d2f4940aA501f9a27B98592589D14Bb0f7
  • Token Cashier Address: 0xf72CFb704d49aC7BB7FFa420AE5f084C671A29be
  • Transfer Validator Address: 0xFBe9A4138AFDF1fA639a8c2818a0C4513fc4CE4B

Crosschain IOTX (WIP)

  • CIOTX on IoTeX: 0x99B2B0eFb56E62E36960c20cD5ca8eC6ABD5557A
  • CIOTX on Polygon: 0x300211Def2a644b036A9bdd3e58159bb2074d388
  • CIOTX on BSC: 0x2aaF50869739e317AB80A57Bf87cAA35F5b60598


📡 A multi-assets, fully decentralized, and tridirectional bridge for exchanging ERC20/BEP20/XRC20 tokens between Ethereum, Binance Smart Chain and IoTeX







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