The full spec table
The 3 minute rule that actually matters
The number people miss is not a technical limit at all. Instagram distributes Reels over 3 minutes to your existing followers but holds them back from new audiences. If the goal of a Reel is discovery, and it usually is, the practical maximum is 3 minutes regardless of what the uploader accepts. Long tutorials belong on YouTube; the Reel is the trailer.
Feed preview cropping
A 9:16 Reel is shown full frame in the Reels tab but cropped towards 4:5 in the main feed preview. Keep the subject and any text in the central 4:5 area of the frame so the feed crop never cuts a head or a headline in half.
Why Reels fail to publish through schedulers
The most common causes we see are an aspect ratio outside Instagram's accepted range, audio muted by licensing, an expired account connection, and files that exceed limits after a high bitrate export. Every one of these is detectable before the scheduled time, which is why SocialPro runs pre flight checks on each Reel rather than discovering the problem when the publish call bounces. If your Instagram connection itself keeps dropping, the disconnection guide below walks through every cause.