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Quick start

Set up and install Blnk for your product.

Blnk is an open source, double-entry ledger for building financial products.

It is very simple to set up, and it takes less than 5 minutes to start using for your product.

Install Blnk

This runs Blnk on your computer. You need Docker and Compose.

Start Blnk

Clone the repository, then start the server:

git clone https://github.com/blnkfinance/blnk && cd blnk
docker compose up

You’ll find your Blnk instance running at http://localhost:5001.

Instead of self-hosting, start with a sandbox on Blnk Cloud.

Deploy a Core

Blnk Cloud homepage with Deploy new Core

Name the instance

Choose a name, then click Deploy managed Core.

Instance form with Deploy managed Core

Wait until it is connected

Deployment takes about 7–10 minutes. When the status is Connected, open the instance to copy the Core URL and secret key.

Record your first transaction

Let’s record a $1,000.00 transaction between two balances.

We’ll use internal balances so that the balances are auto-created when we record the transaction.

Post the transaction

Send this request to http://localhost:5001 on your machine.

If using Blnk Cloud, use the Core URL from your instance and send your secret key as X-blnk-key.

curl -X POST 'http://localhost:5001/transactions' \
  -H 'X-blnk-key: <api-key>' \
  -H 'Content-Type: application/json' \
  -d '{
    "precise_amount": 100000,
    "reference": "first_transaction_001",
    "currency": "USD",
    "precision": 100,
    "source": "@FundingPool",
    "destination": "@MyBalance",
    "description": "My first Blnk transaction",
    "allow_overdraft": true,
    "skip_queue": true,
    "meta_data": {}
  }'

const response = await blnk.Transactions.create({
  precise_amount: 100000,
  reference: 'first_transaction_001',
  currency: 'USD',
  precision: 100,
  source: '@FundingPool',
  destination: '@MyBalance',
  description: 'My first Blnk transaction',
  allow_overdraft: true,
  skip_queue: true,
  meta_data: {},
});

transaction, _, _ := client.Transaction.Create(blnkgo.CreateTransactionRequest{
    ParentTransaction: blnkgo.ParentTransaction{
        PreciseAmount: big.NewInt(100000),
        Reference: "first_transaction_001",
        Currency: "USD",
        Precision: 100,
        Source: "@FundingPool",
        Destination: "@MyBalance",
        Description: "My first Blnk transaction",
        SkipQueue: true,
    },
    AllowOverdraft: true,
})

response = blnk.transactions.create({
  "precise_amount": 100000,
  "reference": "first_transaction_001",
  "currency": "USD",
  "precision": 100,
  "source": "@FundingPool",
  "destination": "@MyBalance",
  "description": "My first Blnk transaction",
  "allow_overdraft": True,
  "skip_queue": True,
  "meta_data": {},
})

ApiResponse<JsonNode> response = blnk.transactions().create(
    CreateTransactions.create()
        .preciseAmount(100000)
        .reference("first_transaction_001")
        .currency("USD")
        .precision(100)
        .source("@FundingPool")
        .destination("@MyBalance")
        .description("My first Blnk transaction")
        .allowOverdraft(true)
        .skipQueue(true)
        .metaData(Map.of()));

Read the response

{
  "id": "txn_6164573b-6cc8-45a4-ad2e-7b4ba6a60f7d",
  "source": "@FundingPool",
  "destination": "@MyBalance",
  "reference": "first_transaction_001",
  "amount": 1000,
  "precision": 100,
  "precise_amount": 100000,
  "currency": "USD",
  "description": "My first Blnk transaction",
  "allow_overdraft": true,
  "status": "APPLIED",
  "created_at": "2024-12-21T01:36:46.997063436Z",
  "meta_data": {}
}

precise_amount is 100000 and precision is 100, so the amount is 1,000.00 USD.

The transaction is recorded. status is APPLIED, and the balances should have been updated with their correct amounts.

In your Blnk Cloud workspace, open Transactions.

Open Create transaction

Click Create transaction in the top right. You can also press ⌥ T (Alt+T on Windows).

Transactions table with Create transaction

Enter the transaction

Fill in the form:

Amount: 1000
Currency: USD
Precision: 100
Source: @FundingPool
Destination: @MyBalance
Description: My first Blnk transaction

Create transaction form

Allow the funding pool to go negative

Under Advanced options, turn on Apply overdraft. @FundingPool has no funds yet, so the transaction needs this.

Apply overdraft turned on

Create the transaction

Click Create transaction. The new row shows in the Transactions table.

The transaction is recorded. Source is @FundingPool and destination is @MyBalance.