What is a ZWO File? The Zwift Workout Format Explained

What is a ZWO file? ZWO stands for Zwift Workout. It is an XML-based file format used by the Zwift platform to store structured workout data. Each .zwo file contains the instructions for a single workout, including interval durations, power targets (as a % of FTP), cadence goals, and on-screen text instructions.

When you use the "Custom Workouts" folder in Zwift, you are reading ZWO files stored on your device.

What ZWO Files Contain

Unlike .fit files which record what you did, .zwo files are instructions for what to do. A ZWO file tells Zwift:

Metadata: Title, description, author, and tags
Structure: The sequence of intervals (Warmup, SteadyState, IntervalsT, etc.)
Targets: How hard to pedal (e.g., "Power=0.95" means 95% of FTP)
Duration: How long each step lasts
Text: Messages that appear on screen ("Pedal hard!", "Recover now")

Where to Find ZWO Files

On a PC or Mac, your custom workouts are stored locally:

Windows: Documents\Zwift\Workouts\[YourZwiftID]
Mac: Documents/Zwift/Workouts/[YourZwiftID]
iOS/Android/AppleTV: Files are synced from the cloud. To add files, you must use a PC/Mac to sync them first.

ZWO File Structure

Because ZWO is XML (text), you can open and edit it in any text editor like Notepad.

<workout_file>
    <author>Jonas</author>
    <name>My VO2 Max Session</name>
    <description>Hard 3-minute intervals.</description>
    <sportType>bike</sportType>
    <workout>
        <Warmup Duration="600" PowerLow="0.5" PowerHigh="0.75"/>
        <IntervalsT Repeat="5" OnDuration="180" OffDuration="180" OnPower="1.15" OffPower="0.55"/>
        <Cooldown Duration="300" PowerLow="0.75" PowerHigh="0.5"/>
    </workout>
</workout_file>

Key Elements:

Warmup/Cooldown: Ramps power from Low to High (or High to Low).
SteadyState: Holds a constant power.
IntervalsT: Repeats a set of On/Off intervals (time-based).
FreeRide: Lets terrain dictate resistance (like a normal ride).

Converting ZWO Files

Sometimes you need to convert ZWO files to use them elsewhere:

ZWO to FIT: To use the workout on a Garmin/Wahoo head unit outdoors.
- Tool: ZWO to FIT Converter
FIT to ZWO: To turn an outdoor ride recording into a Zwift workout.
- Tool: FIT to ZWO Converter

Creating Custom ZWO Files

You can create ZWO files in three ways:

Zwift Workout Editor: Built into the game. Visual and easy to use.
Text Editor: Write the XML code manually (for advanced users).
Third-Party Tools: Sites like zwofactory.com or whatsonzwift.com offer web-based builders.