There is no max length but here's what works best.
There is no time limit for videos in OnForm. However, the app ensures high quality resolution which means longer videos will be much slower to upload because the file sizes will be very large.
We've also found it most useful to focus on a specific skill to improve, rather than, say, reviewing an entire dressage test. For this reason, we suggest videos under 5 minutes and, optimally, videos which are 30 sec to 2 minutes become easier to manage, easier to provide specific feedback on, and are ultimately better for your clients to consume.
Generally, we'd suggest a 15 minute max, but there is no actual time limit.