# Exact Output (toAmount)

## Overview

By default, Squid routes use **exact input** — you specify how much to send (`fromAmount`) and receive the best available output. With **exact output**, you specify how much you want to receive (`toAmount`) and the system calculates the required input amount.

This lets users say "I want to receive exactly X tokens" instead of "I want to send exactly X tokens."

{% hint style="info" %}
Exact output requires the `ExactOutputRouting` feature flag. Contact the Squid team to enable it for your integrator ID.
{% endhint %}

***

## Usage

Specify `toAmount` instead of `fromAmount` in your route request. Exactly one must be provided.

```json
// Forward (existing) — specify how much to send
{
  "fromAmount": "1000000000000000000",
  "fromToken": "...",
  "toToken": "..."
}

// Exact output — specify how much to receive
{
  "toAmount": "1000000",
  "fromToken": "...",
  "toToken": "..."
}
```

The response will include a calculated `fromAmount` representing how much input is needed to receive exactly `toAmount`. The `toAmountMin` will equal the `toAmount` — the output is guaranteed.

***

## Slippage

Slippage works in reverse compared to forward mode:

|            | Forward (fromAmount)         | Exact Output (toAmount)                   |
| ---------- | ---------------------------- | ----------------------------------------- |
| **Output** | May receive less than quoted | **Guaranteed** — `toAmountMin = toAmount` |
| **Input**  | Fixed at `fromAmount`        | May need to send slightly more            |

In exact output mode, slippage is applied to the **input** side. You may need to provide up to `fromAmount × (1 + slippage)` as input. Any unused input tokens are automatically returned to your address.

***

## Supported Route Types

| Route Type                                                  | Supported |
| ----------------------------------------------------------- | --------- |
| EVM single-chain swaps                                      | ✅         |
| EVM-to-EVM cross-chain (Coral V2)                           | ✅         |
| All chains accessible via Coral V2                          | ✅         |
| Routes with post-hooks                                      | ✅         |
| Routes with pre-hooks                                       | ❌         |
| Traditional bridge (Axelar GMP, Chainflip, ITS, Noble CCTP) | ❌         |
| Cosmos routes (Osmosis, Astroport)                          | ❌         |
| Solana single-chain (Jupiter)                               | ❌         |

***

## Limitations

* **Feature flag required** — `ExactOutputRouting` must be enabled for your integrator ID.
* **No pre-hooks** — Pre-hooks are not supported because the input amount is unknown at pre-hook execution time. Post-hooks work normally.
* **Coral V2 only for cross-chain** — Traditional bridge protocols are not supported for cross-chain exact output routes.
* **Some DEXes unsupported** — Paths through Curve, KyberSwap Elastic, Osmosis, Astroport, Printr, or Saddle will fail in exact output mode.


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