---
id: exchange-managing-zrc2-tokens
title: Managing Fungible Tokens (ZRC-2)
keywords:
  - zrc2
  - polling
  - exchanges
  - zilliqa
description: Managing Fungible Tokens (ZRC-2)
---

---

## Introduction to ZRC-2

[ZRC-2](https://github.com/Zilliqa/ZRC/blob/master/zrcs/zrc-2.md) is the formal
standard for Fungible Token in Zilliqa. It is an open standard for creating
currencies on the Zilliqa blockchain.

The ZRC-2 standard allows for functionalities like

- Minting/burning tokens
- Transferring tokens from one account to another
- Querying account token balance
- Querying total token balances
- Approving third party to spend a certain amount of tokens
- Etc.

## Examples of ZRC-2

- [XSGD](https://www.xfers.com) - the first Singapore dollar-pegged stablecoin
  built by Xfers
- [gZIL](https://github.com/Zilliqa/ZIP/blob/master/zips/zip-11.md#governance-tokens-aka-gzil) -
  Governance ZIL token earned through Zilliqa Seed Node Staking Program

## Checking Whether a Contract is ZRC-2 Compliant

Before you start any integration with ZRC-2, it is important to check the smart
contract to ensure it conforms to the ZRC-2 standard. Non-conformance to the
standard may lead to composability issues with other contracts or dApp/exchange
integration.

Please check the
[ZRC-2 specification](../../developers/user-key-management/dev-keys-zrc2-wallet-support.md)
subsection in the Developers section of this developer portal.

## Contract Operations

Please check the
[Integrating with ZRC-2 Fungible Tokens Contract](../../developers/user-key-management/dev-keys-zrc2-wallet-support.md)
subsection on how to get token balance and transfer tokens.

## Tracking Incoming ZRC-2 Deposit

To track any new **incoming deposit** of a specific ZRC-2 token:

1.  Poll the blockchain block by block using API
    [`GetTxnBodiesForTxBlock`](../../api/transaction-related-methods/api-transaction-get-txbodies-for-txblock.md)
    API and process each transactions
1.  For each transaction in the TxBlock, perform the following:

    - Check whether `toAddr` matches the corresponding ZRC-2 token contract
      address. For example, contract address
      [a845c1034cd077bd8d32be0447239c7e4be6cb21](https://viewblock.io/zilliqa/address/0xa845c1034cd077bd8d32be0447239c7e4be6cb21)
      for gZIL ZRC-2 token.

    - Check that the **success** field is set to `true`. If it is `false`, it
      means that this transaction was not accepted by the network.
    - Under `data`, look for `Transfer` or `TransferFrom` tag. Check the `value`
      to see whether it matches the base16 address format of your deposit
      address.
    - If it matches, `value` represents the amount of tokens that are being
      transferred from the sender to your deposit address.

    !!! note

          When handling `value`, please note the number of decimal places used by
          the smart contract.

1.  **[Optional checks]** You can also check `event_logs` and ensure the
    following:
    - `_eventname` matches `TransferSuccess` and `address` matches your deposit
      address
    - Under `params` map:
      - vname `sender` refers to the sender of the transactions
      - vname `recipient` refers your deposit address
      - vname `amount` is the amount of token transferred

Sample transaction receipt of a ZRC-2 token

```bash
{
  "id": "1",
  "jsonrpc": "2.0",
  "result": {
    "ID": "765efeb58c4e4fd314a861155173de85baed90df4fcd9b2a24c8693e611d1970", <-- Transaction hash
    "amount": "0", <-- This is in term of $ZIL and not ZRC-2 token
    "data": "{\"_tag\":\"Transfer\",\"params\":[{\"vname\":\"to\",\"type\":\"ByStr20\",\"value\":\"0xa795895a4cebe56068439858b6b1f4fe09af4c8c\"},{\"vname\":\"amount\",\"type\":\"Uint128\",\"value\":\"475772968079442\"}]}",
    "gasLimit": "3125",
    "gasPrice": "2000000000",
    "nonce": "71",
    "receipt": {
      "accepted": false,
      "cumulative_gas": "492",
      "epoch_num": "895498",
      "event_logs": [
        {
          "_eventname": "TransferSuccess",
          "address": "0xa845c1034cd077bd8d32be0447239c7e4be6cb21", <-- Contract address of ZRC-2 token
          "params": [
            {
              "type": "ByStr20",
              "value": "0x49355e4ec63634266e0b6c8fa3cbc02a76a6dd75",
              "vname": "sender"
            },
            {
              "type": "ByStr20",
              "value": "0xa795895a4cebe56068439858b6b1f4fe09af4c8c",
              "vname": "recipient"
            },
            {
              "type": "Uint128",
              "value": "475772968079442",
              "vname": "amount"
            }
          ]
        }
      ],
      "success": true, <-- Transaction is successful and confirmed on the blockchain
      "transitions": [
        {
          "addr": "0xa845c1034cd077bd8d32be0447239c7e4be6cb21",
          "depth": 0,
          "msg": {
            "_amount": "0",
            "_recipient": "0xa795895a4cebe56068439858b6b1f4fe09af4c8c",
            "_tag": "RecipientAcceptTransfer",
            "params": [
              {
                "type": "ByStr20",
                "value": "0x49355e4ec63634266e0b6c8fa3cbc02a76a6dd75",
                "vname": "sender"
              },
              {
                "type": "ByStr20",
                "value": "0xa795895a4cebe56068439858b6b1f4fe09af4c8c",
                "vname": "recipient"
              },
              {
                "type": "Uint128",
                "value": "475772968079442",
                "vname": "amount"
              }
            ]
          }
        },
        {
          "addr": "0xa845c1034cd077bd8d32be0447239c7e4be6cb21",
          "depth": 0,
          "msg": {
            "_amount": "0",
            "_recipient": "0x49355e4ec63634266e0b6c8fa3cbc02a76a6dd75",
            "_tag": "TransferSuccessCallBack",
            "params": [
              {
                "type": "ByStr20",
                "value": "0x49355e4ec63634266e0b6c8fa3cbc02a76a6dd75",
                "vname": "sender"
              },
              {
                "type": "ByStr20",
                "value": "0xa795895a4cebe56068439858b6b1f4fe09af4c8c",
                "vname": "recipient"
              },
              {
                "type": "Uint128",
                "value": "475772968079442",
                "vname": "amount"
              }
            ]
          }
        }
      ]
    },
    "senderPubKey": "0x03A4738532329F5867A448B32B16DF65AEC51C09CCAE8C972D78E49E9EFC84EF89",
    "signature": "0x73E84B5FB5AE7D46F941E5BC393253EA19EAE8CD2C5FD07A64D553970EFF8FBDB79384730C10310055E79CA560DC9B79A77ED64E5ADC69260EE32185D3AAF20B",
    "toAddr": "a845c1034cd077bd8d32be0447239c7e4be6cb21",  <-- Contract address of ZRC-2 token
    "version": "65537"
  }
}
```

## Other References

- [Sample codes for various ZRC-2 operations](https://github.com/Zilliqa/ZRC/tree/master/example/zrc2)