Acrossbridge transfers: choose what your app promises

Across exposes three transfer types, and each controls a different amount: what leaves your wallet, what arrives, or the minimum you will accept. If you are integrating acrossbridge, choose the type that matches the promise your app makes to its user. The Swap API returns a transaction for the user to sign and submit. You can see the current options at acrossbridge, then build your integration around the amount that matters most.

What does each acrossbridge transfer type control?

Exact input fixes the amount taken from the user, while the amount received can vary with the quote. It is the straightforward choice when your interface starts with “send this much.”

Minimum output fixes the least the user should receive; the input amount can vary to meet that target. Use it when your interface promises an amount on the destination chain, and make the maximum input clear before the user signs.

Exact output asks for a precise destination amount, with the input calculated to cover it. It suits flows where a downstream action needs a known amount, though the user still needs to see how much may be taken on the source chain.

When should an integration use exact input?

Use exact input when the user chooses a spend amount, such as sending 50 units of a token across chains. The quote tells your app what the destination amount is expected to be, so show that estimate and any applicable fees before asking for approval.

This mode also makes the budget easy to understand: the user sets the amount they are willing to spend. It does not promise a fixed amount on arrival, so avoid presenting the estimate as a guarantee.

When is minimum output or exact output a better fit?

Choose minimum output when the user cares about a floor, not an exact destination amount. For example, a wallet can let someone specify the least they want to receive while the quote determines the source amount needed.

Choose exact output when another step depends on receiving a particular amount, such as a deposit or purchase with a fixed requirement. Your integration should present the calculated input and any limit clearly; if conditions change, fetch a fresh quote before the user signs.

• Use exact input when the spend amount is the user’s priority.
• Use minimum output when the user needs a guaranteed floor.
• Use exact output when the next action needs a specific amount.

Acrossbridge integrations should also check that the route supports the chosen tokens and chains, and use the returned transaction data rather than assuming every route behaves alike. Fees and available routes can change, so retrieve a current quote at the time of transfer.

Which transfer type should most apps start with?

For a basic bridge flow, exact input is usually the clearest starting point because the user controls the spend amount directly. Move to minimum output when your product promise is about what arrives, or exact output when a destination action needs a precise amount.

Before launch, test the approval and signing flow, show the user both sides of the quote, and handle a quote that expires or a route that is unavailable. Watch the live route and fee response at each transfer, since that is the signal that tells your app what it can offer next.