ZWO and FIT workout files, explained

What a .ZWO file is

.ZWO is Zwift's workout format — an XML file describing a sequence of blocks (warm-up, steady efforts, intervals, cool-down), each with a duration and a power target as a percentage of FTP. Load it into Zwift and it controls a smart trainer through the whole session automatically, no manual gear changes required.

What a .FIT workout file is

.FIT is the compact binary format Garmin created, now supported broadly across head units and watches — including Garmin, Wahoo, and most other GPS cycling computers. A .FIT workout file describes the same kind of structured session, but instead of running in an app, it's followed directly on the device, with on-screen prompts guiding the athlete through each step during the ride.

Which one your athlete actually needs

If they train indoors on Zwift, they need .ZWO. If they ride with a Garmin, Wahoo, or similar head unit — indoors or out — they need .FIT. Plenty of athletes end up wanting both, depending on the day.

Generating both without touching XML

Hand-writing either format means learning its schema and getting the block structure exactly right. Wattscribe skips that: describe the workout by voice the way you'd coach it, review the structured result, and export it as a .ZWO or a .FIT file — or push it directly to an athlete's intervals.icu account if that's where they train from.