All Operators in Arknights have two base skills; passive abilities which provides bonus to themselves or the RIIC facility they are working on, improving their efficiency in various ways.
All Operators start with their first base skill (except Nian, Dusk and Fiammetta who starts with both), and gains the second base skill at different points depending on their rarity:
- At the maximum level of 30 for 1★ and 2★ Operators.
- When promoted to Elite 1 for 3★ and 4★ Operators.
- When promoted to Elite 2 for 5★ and 6★ Operators.
Certain Operators have their first and/or second base skill upgraded when they are promoted to Elite 1 and/or Elite 2. Few Operators even starts with both base skills that are upgraded when they are promoted to Elite 1 and/or Elite 2.
Most Operators have two identical base skills with the second being more effective than the first and replaces it. Some Operators have base skills with similar effects that do not stack if multiple Operators with such are stationed together in the same facility; instead, the most effective one will take precedence over the others.
Note that base skills will give no effect when the Operator's morale reaches 0, except for those pertaining to morale recovery.