Which cards are legal in MTG Arena's pauper format?

MTG Arena doesn't seem to have information available on which cards are legal in its Pauper format. Does this format only allow cards which have had Common rarity in MTG Arena itself? Or is it simply Standard Pauper? I'm not sure if that's the same thing or not—I just started playing Arena recently and am not sure if there has been a set rotation since it began. I have noticed some cards being played at Uncommon rarity but I think they all have Common printings from another set which are still Standard-legal.
Jon N points out that with the Arena Deckbuilder's Advanced filter set to only show commons, some uncommons will nonetheless appear.
Best Answer
Although there is no official format definition for Arena, Pauper as an older format has always been defined as: "cards with a common printing in allowed sets". So in Arena, this could be translated as:
Any card which has a common printing in Standard (i.e. sets which are legal in Arena), no matter if the specific printing of the card is in other rarity.
Having said that, I don't think currently there is a card with printings at different rarity in Standard sets.
Pictures about "Which cards are legal in MTG Arena's pauper format?"



Can you play uncommon cards in pauper?
While it never rotates like Standard, meaning cards from right across the game's history can be used, only common-rarity cards are legal. Uncommon, rare, and mythic rare cards have no place in the Pauper format. For a card to be legal in Pauper, at least one of its printings has to have been at common rarity.Are Commander cards legal in pauper?
Pauper Commander follows the combined paper/online rarities adopted by Pauper but also allows the use of promo cards. This means cards that have only appeared at the common or uncommon rarity in online sets such as Chainer's Edict and Bastion Protector are legal to play.What magic format allows all cards?
ETERNAL. Eternal formats are unique in that they contain every black-bordered card set Wizards has ever printed, each new card set is added to these formats. Allows cards from all legal sets, but bans certain cards for power level reasons.Is Hyupn tourach legal in pauper?
High Tide, Hymn to Tourach, and Sinkhole Banned in Pauper.Magic the Gathering Bans 98 (!!!!!!) Cards from Standard! WHAT?!?!?!?!
Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
Images: Ron Lach, alleksana, Gaspar Zaldo, Mike van Schoonderwalt