---
title: 'Overview'
description: 'How OneHazel workflows, nodes, and connectors fit together.'
---
# Workflow Nodes

OneHazel is an AI-powered iPaaS (integration platform as a service) that lets you
connect external APIs and orchestrate them into **workflows** — event-driven
automations that run without you writing any code.

This documentation covers three concepts:

- **Connectors** — pre-built integrations for services like Stripe, HubSpot,
  Postmark, and ~280 others. Connectors define *how* to talk to a specific API.
- **Connections** — your authenticated instance of a connector (API keys,
  OAuth tokens, etc.). You can have multiple connections per connector
  (e.g. one Stripe connection for test mode and another for live).
- **Nodes** — the building blocks of a workflow. Each node does one specific
  thing: call an API, branch on a condition, transform data, delay, retry, etc.

## How a workflow runs

1. A **trigger** node starts the workflow. Triggers can be event-driven
   (when an event matching a filter is received), schedule-driven (cron),
   or webhook-driven (external system POSTs to a unique URL).
2. The engine walks the graph, executing each downstream node in order.
   Branching nodes (If/Else, Switch, Try/Catch, Filter, Retry) decide
   which outgoing edges fire based on the node's outputs.
3. Each node writes its result into an implicit execution context that
   downstream nodes can reference using `{{node_id.path.to.field}}`
   template syntax.
4. When every leaf branch finishes, the workflow execution is marked
   complete. You can view every past run under the Workflows tab.

## Referencing data between nodes

Any node that accepts a **data reference** field (marked with the branch
icon in the config drawer) lets you pull values from earlier nodes using
`{{...}}` syntax:

```
{{trigger.data.amount}}
{{stripe_call.data.customer_id}}
{{loop.index}}
```

The data picker inside those fields renders a tree of every value any
upstream node has produced. Pick from the tree and it inserts the correct
reference token — no need to type the path manually.

## Where to go next

- **Triggers** — how workflows start (Event, Schedule, Webhook).
- **Actions** — how workflows *do things* (API Call, HTTP Request, Emit Event).
- **Flow Control** — If/Else, Switch, Loop, Parallel, Merge, Delay.
- **Data** — Transform, Filter, Aggregate.
- **AI** — AI Transform and AI Classify nodes (LLM-powered steps inside a workflow).
- **Error Handling** — Try/Catch and Retry for resilience.
- **Connectors** — reference pages for every connector in the marketplace.