THE SHORT VERSION:

When you post your post is shown to the most engaged and newest followers that are logged into Instagram at that time. This is called your 'sample audience'. If your post doesn't perform well (in terms of engagement ratios) then your post won't get much 'reach'.

When you first post your post is shown to a small group of people. This is called your 'sample audience'.  This usually includes your most engaged followers and your newest followers who happen to be online at this time. 

 

How it works:
Based on the reaction of this audience to your new post, Instagram's algorithm will decide if your post is a high-quality post. If it is very high quality based from this (i.e. it has a lot of engagement) it will give your post more 'reach'.If the reaction is truly exceptional, it will then feature your post on the 'Explore' page, where you can potentially go viral. 

 

Conversely, if when your post goes live it isn't received well by your sample audience - it will be deemed as a low-quality post and be given less reach. 

Manipulating This Rule:
You can make sure that Instagram judges your post as ‘high quality’ by joining our automated comment groups, replying to every single comment to increase comment ratios, using captions with questions to encourage questions etc. This all increasing your post engagement ratios in the first 30 minutes, all of which helps to increase your posts reach and viral potential.