---
url: /docs/formats/zwo.md
description: >-
  Read, write, and validate Zwift workout XML files using @kaiord/zwo. Supports
  all ZWO interval types and power targets.
---

# ZWO Format

The `@kaiord/zwo` package provides reading, writing, and validation of Zwift workout XML files.

## Installation

```bash
pnpm add @kaiord/core @kaiord/zwo
```

## Usage

### Pre-built adapters

```ts twoslash
import { fromText, toText } from "@kaiord/core";
import { zwiftReader, zwiftWriter } from "@kaiord/zwo";
import { readFile, writeFile } from "node:fs/promises";

// ZWO to KRD
const zwoContent = await readFile("workout.zwo", "utf-8");
const krd = await fromText(zwoContent, zwiftReader);

// KRD to ZWO
const zwoString = await toText(krd, zwiftWriter);
await writeFile("output.zwo", zwoString);
```

### Factory with custom logger

```ts twoslash
import { createConsoleLogger } from "@kaiord/core";
import { createZwiftReader, createZwiftWriter } from "@kaiord/zwo";

const logger = createConsoleLogger();
const reader = createZwiftReader(logger);
const writer = createZwiftWriter(logger);
```

## API

| Function                       | Description                                                  |
| ------------------------------ | ------------------------------------------------------------ |
| `zwiftReader`                  | Pre-built ZWO text reader                                    |
| `zwiftWriter`                  | Pre-built ZWO text writer                                    |
| `createZwiftReader(logger?)`   | Factory for ZWO reader with optional logger                  |
| `createZwiftWriter(logger?)`   | Factory for ZWO writer with optional logger                  |
| `createZwiftValidator(logger)` | XSD validator (Node.js) or well-formedness checker (browser) |

## Supported features

* SteadyState intervals
* Warmup and Cooldown ramps
* IntervalsT (structured intervals)
* FreeRide segments
* Power targets (FTP percentage)
* Heart rate and cadence targets
* Text events

## ZWO-specific notes

When converting ZWO to KRD:

* Power targets are expressed as FTP percentage (Zwift's native unit)
* Heart rate targets have limited support in ZWO format
* Distance-based durations may be converted to time-based
* Original ZWO-specific data is preserved in `extensions.zwift`

Ready to convert? Follow the [Quick Start](/guide/quick-start).