Standard format - the main Play Mode format, uses the Core Set + cards from the most recent 2 years of expansions.
After 2 years the cards from expansions “rotate” out of Standard and become Wild only. You are able to play all the old cards in Wild format.
In collection you have to click under the “Wild cards” filter to see all your Wild cards - it shows Standard cards by default.
To switch between playing Wild, Standard, Classic and Casual there is a small button on the top right of the Play screen, which currently shows a Gryphon. Click on that to switch.
Rise of Shadows, Saviors of Uldum, Descent of Dragons, Galakrond’s Awakening, and the Demon Hunter Initiate Set rotated out on 30 March 2021. The Classic and Basic sets moved to Wild and Classic formats only. But of those cards, 88 Classic and 52 Basic cards remain in Standard, now available for free in the Core Set.
Before 30 Mar 2021
Standard format - the main Play Mode format, uses Basic, Classic cards + cards from the most recent 2 years of expansions.
After 2 years the cards from expansions move out of Standard and become Wild only. You are able to play all the old cards in Wild format.
In collection you have to click under the “All cards” filter to see all your Wild cards - it shows Standard cards by default.
To switch between playing Wild and Standard, there is a small button on the top right of the Play screen, which currently shows a Phoenix. Click on that to switch.
Rise of Shadows, Saviors of Uldum, Descent of Dragons, Galakrond’s Awakening, and the Demon Hunter Initiate Set will rotate out some time in April 2021. So you have a bit over 5 months left in Standard for those cards.