mojo exports all video stories in HD.
To be specific, here are the exact pixels dimensions for each output format:
portrait (9:16) - 1080 x 1920
Instagram feed (4:5) - 1080 x 1350
square (1:1) - 1080 x 1080
landscape (16:9) - 1920 x 1080
If you save the video to your camera roll and you play it back there, you will be able to enjoy 1080p quality.
However, when the video is transferred or posted to social platforms - like Instagram, Snapchat, Facebook - some quality issues may occur.
Here are some things to consider when it comes to video quality:
Transferring stories across devices
You should avoid transferring videos between devices using messaging platforms like Whatsapp, Messenger, etc. Those services highly compress the videos to enable quick transfer, to the detriment of quality.
Third party apps that helps transferring files across devices can reduce video quality.
To transfer your story, you can use cloud storage services like iCloud, Dropbox, Google Drive, etc. Those platforms will not compress the videos.
On Instagram, the video quality depends on the speed of the internet connection of the viewer. For instance, you look at a story with a high bandwidth, the quality should be close to 1080p. If you watch the video with a low bandwidth, the resolution and bitrate can be degraded, so that people watch see it without having to wait for the HD video to be downloaded.
Snapchat
Using the Snapchat button in mojo can result in a loss in quality. If you need high quality stories on Snapchat, it can be preferable to save the mojo story to your Photos first, and then import it from your Photos when you are in the Snapchat app.