# FAQ

## What is the difference between Deploy and Transaction?

Casper has two transaction formats:

- **Deploy** - the original format used in Casper 1.x. Still supported by all nodes.
- **TransactionV1** - introduced in Casper 2.0. More efficient, supports new features.

Use `Transaction` (the SDK wrapper class) which holds either format. All builders produce `Transaction`.

Use `putTransaction()` for `Transaction` and `putDeploy()` only for raw `Deploy` objects.

## How do I check my account balance?

```ts
const result = await rpcClient.queryLatestBalance({
  mainPurseUnderPublicKey: publicKey.toHex(),
});
console.log(result.balance.toString()); // in motes
// 1 CSPR = 1,000,000,000 motes
```

## Why do I get `AccountMigratedToEntity`?

Your account was created on Casper 1.x and migrated during the Casper 2.0 upgrade. Use `getLatestEntity` instead of `getAccountInfo`:

```ts
const entity = await rpcClient.getLatestEntity({
  publicKey: publicKey.toHex(),
});
```

## What is a mote?

The smallest unit of CSPR. `1 CSPR = 1,000,000,000 motes (10^9)`. All SDK amounts are in motes as strings to avoid floating point issues.

## How do I call a smart contract?

```ts
const args = Args.fromMap({
  amount: CLValue.newCLUInt256('1000000000'),
  recipient: CLValue.newCLPublicKey(recipientKey),
});

const tx = new ContractCallBuilder()
  .from(senderPublicKey)
  .byHash('hash-contract-abc...')
  .entryPoint('transfer')
  .runtimeArgs(args)
  .chainName('casper')
  .payment(3_000_000_000)
  .build();
```

## What is a URef?

An Unforgeable Reference - a capability token that grants access to a storage location (purse, dictionary, contract state). Format: `uref-{32-byte-hex}-{octal-access-rights}`.

## Does the SDK work in the browser?

Yes. Use `dist/lib.web.js` or import from the package with a bundler. The `eventsource` package provides SSE support in environments without native `EventSource`.

## How do I use hardware wallets?

Get the bytes to sign, send them to the hardware wallet, then set the signature:

```ts
const tx = new NativeTransferBuilder()...build();
const bytesToSign = tx.getTransactionV1()!.hash.toBytes();
// → send bytesToSign to hardware wallet
const signature = await hardwareWallet.sign(bytesToSign);
tx.setSignature(signature, publicKey);
```