Instant exchange API

The following methods are used to empower your service with Changelly exchange features. You can request more features by contacting our developers team. Changelly API is a white-label exchange solution.

Table of contents:

• Basic info
• Fixed Rate Exchange Feature
• Getting started
• Your API extra fee
• Usage
  • Use Case
  • Protocol
  • Authentication
    • Node.js authentication
    • Postman authentication
  • Currency List
  • Minimum Exchangable Amount
  • Estimated Exchange Amount
  • Generating Transaction
  • Identifying The Transaction
  • Getting Exchange Status
  • Socket.io
• Fixed Rate Methods
• KYC/AML Policy
• Support
• Dedicated Support-Line
• Online Transactions History
• Generate API Keys

Basic info

1. Please read for better understanding https://medium.com/@Changelly/changelly-api-to-robust-your-crypto-business-25f5030bc803.
2. Welcome to check these articles on implementation examples in the other crypto wallets: Trezor, BRD, Coinomi, Ginco, Huobi, Jelurida
3. The usage scheme could be useful for you.

Fixed Rate Exchange Feature

1. New way of exchanging the crypto assets
2. 90+ cryptos available for the fixed-rate exchanges
3. Users get the exact amount of money as they expected
4. Less technical support requests on the subject of rate fluctuation and compensation

Getting started

1. Register and get an API key — generate;
2. Read the following documentation;
3. Open an issue if you have any questions;
4. You can also connect at [email protected].

---

Your API extra fee

After setting up an API key you may want to set up your API extra fee.

For example, you may choose to charge a 0.5% fee (we can set up any commission you want). Our fee is fixed at 0.5%. Thus, your users should pay a 1% commission in total.

To set up an extra commission, please email us with a link to your service.

Your API extra commission is included in a result of getExchangeAmount function call. All fees are always in output currency.

Usage

Usage schema

Implementation examples on GitHub:

• Node.js
• C#
• Python
• PHP

Postman Collection and short description of API methods with examples: https://api-docs.changelly.com. You will need to set up authentication to use Postman with our API.

API URL: https://api.changelly.com

SOCKET URL: https://socket.changelly.com

Use Case

Here is simple use case of our exchange API:

1. API — get available at the current moment list of currencies with getCurrencies or getCurrenciesFull method;
2. GUI — ask user for currency pair he wants to exchange. For example, it can be LTC (Litecoin) to ETH (Ethereum);
3. API — get minimum exchangeable amount for selected currency pair with getMinAmount method;
4. GUI — ask user for the amount to exchange;
5. API — call getExchangeAmount method to get estimated ETH amount after exchange;
6. GUI — show an estimated amount to user and ask for confirmation;
7. GUI — ask user for his wallet address to send coins after exchange;
8. API — call createTransaction method to get the LTC address to which user should send his funds;
9. GUI — ask user to send LTC coins to the address for exchange;
10. User sends LTC. We receive LTC and exchange it for ETH. We send ETH to the address that was submitted to createTransaction method;
11. Via socket.io API functions you can get the user's transaction status online;
12. Via getTransactions method you can get all the transactions history.

Protocol

Changelly API uses JSON-RPC 2.0 protocol.

Example request:

{
   "jsonrpc": "2.0",
   "id": "test",
   "method": "getMinAmount",
   "params": {
      "from": "ltc",
      "to": "eth"
   }
}

Example response:

{
   "jsonrpc": "2.0",
   "id": "test",
   "result": "0.0008563"
}

Id used is a custom ID generated at the client side to distinguish responses. You may use any value you want.

Authentication

All requests must contain the following headers:

Header	Description
api-key	your api key
sign	the query's serialized body signed by your key's "secret" according to the HMAC-SHA512 method

Node.js authentication

Example of how to sign a request with node.js crypto module:

const crypto = require("crypto");

const message = {
  "jsonrpc": "2.0",
  "id": "test",
  "method": "getMinAmount",
  "params": {
    "from": "ltc",
    "to": "eth"
  },
};

const sign = crypto
   .createHmac('sha512', apiSecret)
   .update(JSON.stringify(message))
   .digest('hex');

Postman authentication

Here is a small guide how to properly sign transaction with postman:

1. Add new environment.

2. Add sign and api-key variables to the new environment.

3. Create new request. Being on the Headers tab add sign and api-key headers. Use postman variable syntax for them in Value column. These variables will be updated for each request using the pre-request script.

4. Paste the following code to the Pre-request Script tab for the request. Fill up the apiKey and secret variables. Be very careful not to accidentally share your secret.

const crypto = require('crypto-js')

const apiKey = ''
const secret = ''

const sign = crypto.HmacSHA512(request.data, secret).toString()

postman.setEnvironmentVariable('apiKey', apiKey)
postman.setEnvironmentVariable('sign', sign)

Currency List

Commands getCurrencies and getCurrenciesFull will return you the currency list available for exchange. Check the list of available currencies at Supported currencies page before you start. Example request:

{
   "jsonrpc": "2.0",
   "id": "test",
   "method": "getCurrencies",
   "params": {},
}

Example response:

{
   "jsonrpc": "2.0",
   "id": "test",
   "result": [
      "btc",
      "ltc",
      "eth",
      "doge",
      "xrp",
      "xem",
      "lsk",
      "xmr",
      "zec"
   ]
}

Note and warning: getCurrencies returns a list of currently enabled currencies. We can disable and enable any currency at any time and the response list will reflect the change. Use getCurrenciesFull to get list of all available currencies along with description and state.

Minimum Exchangable Amount

To proceed with exchange we need it to be larger than the certain amount. Use getMinAmount with a currency pair (from, to) to notify users of the minimum amount they need to send.

Example:

{
   "jsonrpc": "2.0",
   "id": "test",
   "method": "getMinAmount",
   "params": {
      "from": "ltc",
      "to": "eth",
   }
}

Example response:

{
   "jsonrpc": "2.0",
   "id": "test",
   "result": "0.0008563"
}

NOTE: most of the users do not read the information about the minimum amount. Be sure to highlight this information in your UI. If users send less than the minimum amount, their coins will likely be lost.

Estimated Exchange Amount

You can show users the estimated amount of coins they receive as a result of exchange using getExchangeAmount. You need to provide the request with currency pair (from, to) and the amount user is going to exchange. Estimated result property includes Changelly plus partner extra fee. All fees are always in output currency. Your API extra fee will decrease the estimated result.

Example:

{
   "jsonrpc": "2.0",
   "id": "test",
   "method": "getExchangeAmount",
   "params": {
      "from": "ltc",
      "to": "eth",
      "amount": "3.99"
   },
}

Example response:

{
   "jsonrpc": "2.0",
   "id": "test",
   "result": "0.72596439091239070521"
}

To get rate for multiple currency pairs, you just have to pass array of arguments, i.e. for one currency pair:

{
   "jsonrpc": "2.0",
   "id": "test",
   "method": "getExchangeAmount",
   "params": [{
      "from": "ltc",
      "to": "eth",
      "amount": "3.99"
   }, {
      "from": "dash",
      "to": "xmr",
      "amount": "3.99"
   }]
}

Example response:

{
   "jsonrpc": "2.0",
   "id": "test",
   "result": [
      {
         "from": "ltc",
         "to": "eth",
         "amount": "3.99",
         "result": "0.7259643909123907"
      },
      {
         "from": "dash",
         "to": "xmr",
         "amount": "3.99",
         "result": "7.08872889023993085566"
      }
   ]
}

Generating Transaction

After a successful call of createTransaction method you get a unique id to track the transaction status and a payin address for user to send money to.

createTransaction, once get called, creates a pair of deposit and payout address. If somebody sends coins to the same address twice, without second call to createTransaction, the coins will be exchanged and sent to the user's payout address.

Property	Required or optional	Description
from	required	currency to exchange from
to	required	currency to exchange for
address	required	recipient address
extraId	optional	property for addresses of currencies that use additional ID for transaction processing (XRP, STEEM/SBD, XLM, DCT, XEM)
refundAddress	optional	used in case of refund
refundExtraId	optional	same as of extraId but for refundAddress

Example request:

{
   "jsonrpc": "2.0",
   "id": "test",
   "method": "createTransaction",
   "params": {
      "from": "doge",
      "to": "ltc",
      "address": "<<valid ltc address>>",
      "extraId": null,
      "amount": 1
   }
}

Example response:

{
   "jsonrpc": "2.0",
   "id": "test",
   "result": {
      "id": "jev5lt0qmg26h48v",
      "apiExtraFee": "0",
      "changellyFee": "0.5",
      "payinExtraId": null,
      "payoutExtraId": null,
      "amountExpectedFrom": 1,
      "amountExpectedTo": 3.99,
      "status": "new",
      "currencyFrom": "eth",
      "currencyTo": "ltc",
      "amountTo": 0,
      "payinAddress": "<<doge address to send coins to>>",
      "payoutAddress": "<<valid ltc address>>",
      "createdAt": "2018-09-24T10:31:18.000Z"
   }
}

Example response fields:

Property	Description
id	Transaction ID. Could be used in getStatus method
apiExtraFee	Your API Extra fee in percents
changellyFee	Changelly fee in percents
payinAddress	Address for a user to send coins to
payinExtraId	ExtraId for payinAddress in case it is required
payoutAddress	Address where the exchange result will be sent to
payoutExtraId	ExtraId for payoutAddress in case it is required
amountExpectedFrom	amount from createTransaction
amountExpectedTo	result from getExchangeAmount at the moment of createTransaction
status	Transaction status
currencyTo	Ticker of input currency
currencyFrom	Ticker of output currency
amountTo	Real amount after the exchange that was sent to payoutAddress
createdAt	Point of time when the transaction was created

Example 2 request:

{
  "jsonrpc": "2.0",
  "id": "test",
  "method": "createTransaction",
  "params": {
    "from": "doge",
    "to": "ltc",
    "address": "<<valid ltc address>>",
    "extraId": null,
    "amount": 1,
    "refundAddress": "<<valid doge address to make automatic refund in case of transaction fail>>",
    "refundExtraId": null
  },
}

Example 2 response:

{
   "jsonrpc": "2.0",
   "id": "test",
   "result": {
      "id": "pgj49c80p572minj",
      "apiExtraFee": "0",
      "changellyFee": "0.5",
      "payinExtraId": null,
      "payoutExtraId": null,
      "refundAddress": "<<doge refund address>>",
      "refundExtraId": null,
      "amountExpectedFrom": 1,
      "status": "new",
      "currencyFrom": "eth",
      "currencyTo": "ltc",
      "amountTo": 0,
      "payinAddress": "<<doge address to send coins to>>",
      "payoutAddress": "<<valid ltc address>>",
      "createdAt": "2018-09-24T10:33:39.000Z"
   }
}

Note: amountTo: 0 is expected. amountTo will have non-zero value when transaction is in finished state.

Identifying The Transaction

To identify transaction the id from the createTransaction method is used.

Also you can use getTransactions method to list all transactions that satisfy request params.

Note on transaction processing: It's common situation when there are many transactions in waiting status when processing payin. In this case transaction with waiting status and the nearest amount is selected. And in case there are many - the earleast of them is selected. If the are no transactions in waiting status then new transaction is created automatically.

All parameters for this method are optional.

Parameter	Description
currency	currencyFrom to filter
address	sender address to filter
extraId	use if address needs any extraId
limit	how many records to retreive
offset	records cursor

Example request:

{
   "jsonrpc": "2.0",
   "id": "test",
   "method": "getTransactions",
   "params": {
      "currency": "doge",
      "address": "<<payin address to search>>",
      "extraId": null,
      "limit": 10,
      "offset" : 10
   }
}

Example response:

{
   "jsonrpc": "2.0",
   "id": "test",
   "result": [{
      "id": "pgj49c80p572minj",
      "createdAt": 1537785219,
      "moneyReceived": 0,
      "moneySent": 0,
      "payinConfirmations": "0",
      "status": "waiting",
      "currencyFrom": "doge",
      "currencyTo": "ltc",
      "payinAddress": "<<payin address>>",
      "payinExtraId": null,
      "payinHash": null,
      "amountExpectedFrom": "1",
      "payoutAddress": "",
      "payoutExtraId": null,
      "payoutHash": null,
      "refundHash": null,
      "amountFrom": "",
      "amountTo": "0",
      "networkFee": null,
      "changellyFee": "0.5",
      "apiExtraFee": "0"
   }, {
      "id": "7kcc21x5z66f5vv9",
      "createdAt": 1535638050,
      "moneyReceived": 1535638050,
      "moneySent": 0,
      "payinConfirmations": "1",
      "status": "confirming",
      "currencyFrom": "btc",
      "currencyTo": "doge",
      "payinAddress": "<<payin address>>",
      "payinExtraId": null,
      "payinHash": "txid4",
      "amountExpectedFrom": "0",
      "payoutAddress": "<<payout address>>",
      "payoutExtraId": null,
      "payoutHash": null,
      "refundHash": null,
      "amountFrom": "1",
      "amountTo": "0",
      "networkFee": null,
      "changellyFee": "0.5",
      "apiExtraFee": "0"
   }]
}

Note: first

Getting Exchange Status

With the transaction ID, obtained from createTransaction call, you can get exchange status to notify your user or provide additional support.

Example:

{
   "jsonrpc": "2.0",
   "id": "test",
   "method": "getStatus",
   "params": {
      "id": "pgj49c80p572minj"
   }
}

Example response:

{
   "jsonrpc": "2.0",
   "id": "test",
   "result": "waiting"
}

Possible transaction statuses:

Status	Description
waiting	Transaction is waiting for an incoming payment.
confirming	We have received payin and are waiting for certain amount of confirmations depending of incoming currency.
exchanging	Payment was confirmed and is being exchanged.
sending	Coins are being sent to the recipient address.
finished	Coins were successfully sent to the recipient address.
failed	Transaction has failed. In most cases, the amount was less than the minimum. Please contact support and provide a transaction id.
refunded	Exchange failed and coins were refunded to user's wallet. The wallet address should be provided by user.
overdue	We did not receive any payment since 36 hours from transaction creation.
hold	Due to AML/KYC procedure, exchange may be delayed

Socket.io

As well as JSON RPC, the API provides socket.io interface for receiving exchange status. The subscription should be signed and have a valid logon message.

Key	Description
sign	message object signed with your secret using hmac sha512 method
message	logon message object to sign

Events:

Event	Trigger condition
status	any of transaction properties are changed
payin	payin status gets confirmed
payout	transaction status became finished or failed

Example:

socket.on("connect", function() {
  socket.emit("subscribe",
    {
   "apiKey": apiKey,
   "sign": sign,
   "message": {
       "Login": {}
     }
   }
  );
});

socket.on("status", function(data) {
  console.log(data);
});

Event data example:

{
   "id": "adfa2359b68d",
   "status": "finished",
   "payinConfirmations": "10",
   "hash": "9f19186213799b82776c6792238c6b1c016404bb7003346f890bf754b36f69ca",
   "payinHash": "9f19186213799b82776c5792238c6b1c016504bb7003346f890bf754b36f69ca",
   "payoutHash": "0x1d04f3df2f7209ca985895ecf2e31a07e04889367d37d98c1e8d90fdfb568ec8",
   "payinAddress": "NBLQ6PE7Z5CVANJNXGOR74UQLOJ2YMGJJOZ4YFAQ",
   "payinExtraId": "7c5aefb158ec11e7bbdcafa2978ff15b",
   "payoutAddress": "0x988fa9Bb5C0a462932d9C714E2643a4692E4ABc5",
   "payoutExtraId": null,
   "currencyFrom": "ltc",
   "currencyTo": "eth",
   "amountFrom": "10",
   "amountTo": "0.2",
   "networkFee": "0.01"
}

Fixed Rate Methods

For fixed-rates we’ve added two methods in our API: getFixRate and createFixTransaction.

Getting the Fixed Rate

API Call - getFixRate

Request params example:

[{ "from": "eth", "to": "btc" }, { "from": "trx", to:" eth" }, ...]

Response example:

[{ "from": "eth", "to": "btc", "min": 0.1, "max": 3, "id": "xxx", "result": 31 }, { "from": "trx", to:" eth", "min": 100, "max": 10000, "rateId": "yyy", "id": "yyy", "result": 0.001 }, ...]

• “Max” and “min” params here denote the frame, inside of which we would be able to perform the fix rate exchange and give to the user the exact amount of assets that was shown initially
• getFixRate returns rateId that can be used for 5 minutes. This time should be enough for user to initiate the exchange
• id has to be stored somewhere and will be used as rateId param while calling
• Expired rateId cannot be used for creation of the fixed-rate transaction
• ‘getFixRate’ is designed for bulk requests
• result is a parameter that you can show to the user as the exchange rate
• Important: users shall send the exact amount of funds which were specified as a pay-in amount. In case, users send different sum - the transaction would be automatically refunded
• Important: for fixed rate transactions to process successfully, refund address must be presented as well as refund extraId if needed

Creating a fixed rate transaction

• Using createFixTransaction call you shall add the same params as with the createTransaction float rates method adding only rateId
• Important: in response there will be same fields presented as with the float rate api with amountExpectedTo. The number shown in the amountExpectedTo should be understood as a pay-out amount to the user

KYC/AML Policy

1. Kindly note that we have AML/KYC policy;
2. Due to this policy, users’ transactions may be held for KYC procedures;
3. That is why, before users start an exchange via our API, please, notify them about the possibility of holding the transactions for KYC procedures;
4. You may want to use the following text: “Exchange services provided by Changelly. By clicking “Accept”, I acknowledge and understand that my transaction may trigger AML/KYC verification according to Changelly AML/KYC”;
5. The text may appear in a form of a pop-up window, you are welcome to check the examples of a desktop version notification and a mobile version notification;
6. We also propose you to notify the users when their transaction is held for KYC, using API ‘Hold’ status. You are welcome to check the example of such notification.

Support

Dedicated Support Line

Changelly provides two options for support. Please choose your support line and inform us at [email protected]:

— You just redirect users to our support line;

— You provide the first line support from your side and send your tickets directly to our dedicated email address. These tickets are forwarded strictly to our second level support team. It will be assigned the highest priority. Please don't make our email public.

Inform us in case the dedicated support line is needed. Feel free to request it at [email protected].

Also, send us a link to your service, confirm that you are ready to provide support from your side and you won’t share this email with your clients.

The support line option is provided at the discretion of the Changelly's developer team.

Online Transactions History

You can check all the transactions with online stats on the history page in your personal account.