# Triggers

While workflows can be instantiated using our API, calling them from existing web2 applications is only one use-case.

{% hint style="info" %}
Triggers start new workflow executions, but you can also send [signals](/core-concepts/signals.md) to already running workflows.
{% endhint %}

There are four methods to trigger workflows in two categories:

### Off-chain triggers

1. **API triggers.** See the API documentation in the left navigation.
2. **Webhook triggers.** Similar to API triggers, webhook triggers allow you to start workflows from any 3rd party app that supports webhook notifications. Just create a custom webhook endpoint in the Wundaflow UI and you're good to go.
3. **Time-based triggers**. Workflows can be executed on a given date-time or, using cron-syntax, regularly on any schedule down to per minute.

### On-chain triggers

1. **Logic triggers**. Workflows are executed based on custom logic conditions being met on the blockchain. *Supported: Bitcoin, Ethereum, Base, BNB Chain, Polygon*.

#### Logic trigger examples:

* **Smart contract address or addresses**. A workflow is executed on any interaction with the contract address.<br>
* **Smart contract balance**. A workflow is executed when a given balance is reached.<br>
* **Smart contract method**. A workflow is created when a specific method is called on a given smart contract address. This is particularly useful for creating NFT-connected workflows or those involving gaming assets. We use this extensively for both Wundaflip and Blobbs NFT.<br>
* **Transaction amount**. A workflow is created based on the value of a given transaction in the native currency/token.<br>
* **Block number**. A workflow is created when the block number is mined.


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