Skills

A skill is a capability a character may have, and a specific aspect of an ability score. Rolling for success on a skill is usually called making an ability check. Proficiency in a skill indicates a focus or talent in the capability. Almost everything has at least some skills that give it an edge in performing certain tasks or stunts.

For example, Stealth is a commonly used skill. It is a Dexterity check made when determining how well hidden a character is, or how well they sneak around without being detected. A character proficient in Stealth is notably good at Dexterity checks made to sneak and hide.

Proficiency
Proficiency in a skill allows a character to add their proficiency bonus to rolls made with the skill. All skill rolls will use the ability score modifier they're associated with, but proficiency enables a higher bonus. One without proficiency is just a normal ability check.

Most of a character's skill proficiencies are determined upon character creation, though more can be acquired through class features or feats.

While proficiency is used to indicate a particular talent, it is not the final word on capability. It's possible for a character without proficiency to roll higher than someone who does. However, some GMs may require checks that only those who are proficient in the certain skill can make, meaning that the subject of the check is obscure enough that only characters who specialize in the field would know about it.

Expertise
Expertise is a special type of proficiency. It allows a character to add their proficiency bonus twice to the skill roll they make. You cannot have expertise in a skill you don't first have proficiency in.

In official terms, only bards and rogues can gain expertise. Other classes feature it, but word it as adding double your proficiency bonus instead of labeling it as expertise. Among players, all instances of adding your proficiency bonus twice is called expertise for ease of communication.

Acrobatics
Acrobatics is a skill used when trying to maintain balance or general nimbleness. Examples include walking across a thin or rickety bridge, running along a slippery surface, or moving out of the way of a projectile. It can also be used to break free of a grapple.

Animal Handling
When dealing with animals, Animal Handling is called upon to determine how well that goes. Situations that might call for it range from calming a spooked horse or agitated wild animal, or petting a creature you find. It may also be used when trying to figure out an animal's intentions and instincts.

Arcana
Arcana is used for recalling magical lore. This can include but is not limited to deciphering spells or summoning circles, determining magic items, knowing the planes of existence and its inhabitants, reading eldritch symbols, and remembering or understanding magic rites or rituals.

Athletics
Athletics checks are used when determining feats of endurance, usually when difficulty is encountered while climbing, jumping, or swimming. Examples include trying to scale a steep or slippery cliff, trying to make an unusually long jump, and resisting the pull of tides or monsters while swimming. It's also used when grappling a creature, and can be used to break free of a grapple.

Deception
Deception is used when lying. This can be verbally or not. If you're attempting to convince others of something untrue, Deception is called for. Using disguises, hiding the truth of situations, conning someone, and other situations of ambiguous truth all use Deception.

History
Much like the name suggests, History is used when recalling lore of the past. This can include wars big or small, legendary people, ancient kingdoms or lost civilizations, and miscellaneous historical events. It's also occasionally used when the name of an obscure land is brought up and determining if anyone knows of it.

Insight
Insight is a famous and frequently used skill. Primarily, it's used to determine if someone is being truthful or not. It can also be used to glean how suspicious someone may be, if they're hiding something even if not lying, and any other situation which calls for studying a creature's behaviors and what can be learned from it.

Intimidation
When trying to scare someone through threats, Intimidation is used. This can be through words alone, threatening to do something violent; or pulling out a dagger in a silent show. Intimidation can be applied to multiple situations, such as trying to get information out of a prisoner, convincing someone to reconsider their decisions, or showing off your lack of tolerance for nonsense.

Investigation
Not to be confused with Perception, Investigation determines what you're able to deduce about your surroundings or what you're studying. You might be able to figure out what weapon killed someone, locations of hidden doors or objects, weak points in structure, or the important bit of knowledge in a large book of text.

Medicine
Medicine checks are mostly used to stabilize a dying creature. The DC to do so is 10. It can also be used to diagnose illnesses and occasionally used when determining how something died.

Nature
Nature checks are used when remembering lore about nature. This includes terrain, plants and which might be safe to eat, animals and their behaviors, the weather, and natural cycles.

Perception
Perception is among the most well-known skills, and is frequently mistakenly used in place of investigation. It's used to determine how much a character notices of their surroundings. This can be intentional or not. It relies on basic senses rather than contemplative thought or deductions. Situations that might call for perception include standing guard, eavesdropping, and detecting hidden creatures or subtle sights.

Performance
Performance checks are used when entertaining audiences. This can range from playing music to telling stories. It can, on occasion, also replace Deception or Intimidation if the act is dramatic enough. It determines how well a character can exaggerate to impress others.

Persuasion
Persuasion is used when trying to convince others your way. It is distinct from Deception and Intimidation because it's not through lies or threats, but convincing arguments, tact, social graces, and good nature. It's used when acting in good, honest faith. Situations that call for persuasion include convincing guards to let you speak to a noble, settling disputes between warring groups, or inspiring crowds into action.

Religion
Religion is used when remembering religious lore, such as deities of your pantheon or not, rites and prayers, holy symbols, religious hierarchies and organizations, and even the practices of cults.

Sleight of Hand
Commonly associated with thievery, Sleight of Hand is used in situations that requires careful hand work. While attempting to pickpocket someone does require it, other examples include hiding an object on your person or planting something on someone else. It may also be called upon when doing activities that require fine movements, such as carving.

Stealth
Stealth checks are among the most common. They are used to determine how sneaky a character is being. Situations that use Stealth include slipping past guards, escaping situations unnoticed, hiding from enemies, or sneaking up on someone for a surprise.

Survival
Survival is a skill used for dealing with the wilds. Situations that can call for Survival include tracking footprints, foraging for food or water, navigating wilderness, identifying signs of creatures nearby or living in the area, predicting the weather, and avoiding hazards such as pits or quicksand.

Skills by Ability Score
Skills are directly linked to ability scores. Each skill is marked to which it's typically used in. If a skill is written without an ability specified, that means it uses its default ability.

Strength

 * Athletics

Dexterity

 * Acrobatics
 * Sleight of Hand
 * Stealth

Constitution
No skills are innately related to Constitution.

Intelligence

 * Arcana
 * History
 * Investigation
 * Nature
 * Religion

Wisdom

 * Animal Handling
 * Insight
 * Medicine
 * Perception
 * Survival

Charisma

 * Deception
 * Intimidation
 * Performance
 * Persuasion

Skills with Different Abilities
While skills almost always use their usual associated ability, in some cases, a GM might ask for a different ability to be used, or a player can request to use a different ability.

One of the most well-known instances of this is Intimidation. While normally a Charisma check, Strength can also be used for it if a character is attempting to scare someone through a show of power, not through words. In this case, a Strength check would be made instead of Charisma, and thus the character's Strength modifier would be used. If they have proficiency in Intimidation, then they can also add their proficiency bonus to this Strength check.

Passive Checks
A passive check is an ability check that doesn't involve any die rolls. Instead, it's assumed that the roll is 10, and any relevant modifiers are applied. If a character has advantage, 5 is added, meaning it's assumed the roll is 15. If they have disadvantage, then 5 is subtracted, so the roll is assumed to be 5. Passive checks always use their default ability score.

Passive Perception
While any skill can be used passively, the most famous and used of these is passive perception. It describes how aware a character is of their surroundings even without paying attention. It is frequently used to determine if a character can detect a sneaking or hidden monster. Many players see this as possibly saving their lives and place great importance on passive perception. It can also be used to notice robbery, notable background events, or any other indirect but important detail.

Passive perception can also be used against characters when they attempt Stealth checks. If the Stealth roll is lower than the enemy's passive perception, then the enemy will notice the sneaking character.

Passive Investigation
A lesser-known passive check is passive investigation, which is noted in the Observant feat. It follows the same rules as any other passive check. However, passive investigation is used to determine what a character can deduce just from looking, while passive perception is determining if they even notice the subject.

Passive investigation can completely negate the need for rolling, which runs the risk of rolling lower than 10. It also negates the need for physical handling of the subject, which isn't always available if you're looking at a guarded artifact from afar, or may allow you to notice traps and how they work without risking activating them.