Microsoft has begun preparations for the next one feature update of Windows 10 "21H1" due to its expected release in the first half of 2021.
In 2021, Microsoft will do the opposite to adjust the release rate of major Windows 10 updates. 
So the version 21H1 will be a small update and Microsoft has already completed the changes that will be included in it.
Windows 10 21H1, which is a small press release service pack, will be released in the spring (between April and May) and will be followed by a major renewal design codenamed "Sun Valley" or "21H2" in the fall.
According to reports found in the Windows 10 KB4598291 update, Microsoft has finally started testing the activation package that will update your device to "21H1 version".
This also confirms that the Windows 10 Spring 2021 update will be a small download, at least if you upgrade from 20H2 and 20H1.
Ουσιαστικά, η λήψη των Windows 10 21H1 θα είναι ένα απλό “on switch” ή ένα μικρό πακέτο ενεργοποίησης, το οποίο θα επιτρέψει την λειτουργία μιας νέας δυνατότητας που υπάρχει ήδη στις τελευταίες αθροιστικές ενημερώσεις για την έκδοση 20H2 (October 2020 Update).
However, if you upgrade from an older version of Windows 10, the size of the 21H1 will be larger than 3 GB. If you are using the 20H2 version (October 2020 Update) and you have not installed the latest update, the download size will be smaller from 500MB.
Windows 21 version 1H10 isn't expected to be released until April or May 2021, meaning the update will be tested by users in Release Preview Ring for the coming months.
