> ## Documentation Index
> Fetch the complete documentation index at: https://developer.uphold.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Card transfer integration overview (debit and credit cards)

> Let users fund accounts and cash out with debit or credit cards in EUR, GBP, or USD. Covers card linking, 3DS authorization, and card limits.

Allow users to fund or cash out with their debit/credit cards, globally, in EUR, GBP, or USD.

## Key concepts

* **External account lifecycle** — when a card is added, its status starts as `processing` and transitions to `ok` once validated, or `failed` if the card is invalid or declined. If using the Payment Widget, card-linking specific errors (duplicates, country mismatch, card limits) are handled internally.
* **3DS authorization** — when the transaction response includes a `confirmationUrl` on the card node, 3DS needs to be fulfilled. Either handle the redirect in your app or use the Payment Widget to manage the authorization flow.
* **Card limits** — users may be subject to active card limits and unique card limits. These are enforced as capability restrictions.

## Testing in sandbox

Use [Test cards](/rest-apis/core-api/accounts/test-helpers/fund-sandbox-accounts#test-cards) to simulate card deposits and withdrawals in the Sandbox environment. The table lists card numbers by network, type, and country, along with reserved amounts that trigger specific error responses.

## Start building

<CardGroup cols={2}>
  <Card title="Deposit via API" icon="code" href="/developer-guides/card-transfers/deposit/via-rest-api">
    Set up card deposits and handle 3DS authentication programmatically.
  </Card>

  <Card title="Deposit via Widget" icon="puzzle-piece" href="/developer-guides/card-transfers/deposit/via-payment-widget">
    Let users add their card and deposit funds with a low-code, embeddable widget.
  </Card>

  <Card title="Withdrawal via API" icon="code" href="/developer-guides/card-transfers/withdrawal/via-rest-api">
    Create quotes and submit payouts to your users' cards.
  </Card>

  <Card title="Withdrawal via Widget" icon="puzzle-piece" href="/developer-guides/card-transfers/withdrawal/via-payment-widget">
    Let users withdraw funds to their card with a low-code, embeddable widget.
  </Card>
</CardGroup>