Your Perception measures your ability to notice things, search for what’s hidden, and tell whether something about a situation is suspicious.

Perception is frequently used for rolling initiative in an encounter, and for the Seek action.

Light

There are three levels of light: bright light, dim light, and darkness. The rules in this book assume that all creatures are in bright light unless otherwise noted. A source of light lists the radius in which it sheds bright light, and it sheds dim light to double that radius.

Bright Light

In bright light, such as sunlight, creatures and objects can be observed clearly by anyone with average vision or better.

Dim Light

Areas in shadow or lit by weak light sources are in dim light. Creatures and objects in dim light have the concealed condition, unless the seeker has darkvision or low-light vision, or a precise sense other than vision.

Darkness

A creature or object within darkness is hidden or undetected unless the seeker has darkvision or a precise sense other than vision. A creature without darkvision or another means of perceiving in darkness has the blinded condition while in darkness, though it might be able to see illuminated areas beyond the darkness. If a creature can see into an illuminated area, it can observe creatures within that illuminated area normally. After being in darkness, sudden exposure to bright light might make you dazzled for a short time, as determined by the GM.

Senses

The ways a creature can use Perception depend on what senses it has. The primary concepts you need to know for understanding senses are precise senses, imprecise senses, and the three states of detection a target can be in: observed, hidden, or undetected. Vision, hearing, and scent are three prominent senses, but each has a different degree of acuity.

Precise Senses

Average vision is a precise sense—a sense that can be used to perceive the world in nuanced detail. The only way to target a creature without having drawbacks is to use a precise sense. You can usually detect a creature automatically with a precise sense unless that creature is hiding or obscured by the environment, in which case you can use the Seek basic action to better detect the creature.

Imprecise Senses

Average hearing is an imprecise sense—it can’t detect the full range of detail that a precise sense can. You can usually sense a creature automatically with an imprecise sense, but it has the hidden condition instead of the observed condition. It might be undetected by you if it’s using Stealth or is in an environment that distorts the sense, such as a noisy room in the case of hearing. In those cases, you have to use the Seek basic action to detect the creature. At best, an imprecise sense can be used to make an undetected creature (or one you didn’t even know was there) merely hidden—it can’t make the creature observed.

Vague Senses

A character also has many vague senses—ones that can alert you that something is there but aren’t useful for zeroing in on it to determine exactly what it is. The most useful of these for a typical character is the sense of smell. At best, a vague sense can be used to detect the presence of an unnoticed creature, making it undetected. Even then, the vague sense isn’t sufficient to make the creature hidden or observed.

When one creature might detect another, the GM almost always uses the most precise sense available.

Pathfinder’s rules assume that a given creature has vision as its only precise sense and hearing as its only imprecise sense. Some characters and creatures, however, have precise or imprecise senses that don’t match this assumption. For instance, a character with poor vision might treat that sense as imprecise, an animal with the scent ability can use its sense of smell as an imprecise sense, and a creature with echolocation or a similar ability can use hearing as a precise sense. Such senses are often given special names and appear as “echolocation (precise),” “scent (imprecise) 30 feet,” etc.

Special Senses

While a human might have a difficult time making creatures out in dim light, an elf can see those creatures just fine. And though elves have no problem seeing on a moonlit night, their vision can’t penetrate complete darkness, whereas a dwarf’s can. Special senses allow a creature to ignore or reduce the effects of the undetected, hidden, or concealed conditions when it comes to situations that foil average vision.

Darkvision and Greater Darkvision

A creature with darkvision or greater darkvision can see perfectly well in areas of darkness and dim light, though such vision is in black and white only. Some forms of magical darkness, such as a 4th-rank darkness spell, block normal darkvision. A creature with greater darkvision, however, can see through even these forms of magical darkness.

Low-Light Vision

A creature with low-light vision can see in dim light as though it were bright light, so it ignores the concealed condition due to dim light.

Scent

Scent involves sensing creatures or objects by smell, and is usually a vague sense. The range is listed in the ability, and it functions only if the creature or object being detected emits an aroma. If a creature emits a heavy aroma or is upwind, the GM can double or even triple the range of scent abilities used to detect that creature, and the GM can reduce the range if a creature is downwind.

Tremorsense

Tremorsense allows a creature to feel the vibrations through a solid surface caused by movement. It is usually an imprecise sense with a limited range (listed in the ability). Tremorsense functions only if the detecting creature is on the same surface as the subject, and only if the subject is moving along (or burrowing through) the surface.

Detecting Creatures

Three conditions measure the degree to which you can sense a creature: observed, hidden, and undetected. However, the concealed and invisible conditions can partially mask a creature, and the unnoticed condition indicates you have no idea a creature is around. With the exception of invisible, these conditions are relative to the viewer—it’s possible for a creature to be observed to you but hidden from your ally. Most of these rules apply to objects as well as creatures. Typically, the GM tracks how well creatures detect each other, since neither party has perfect information. For example, you might think a creature is in the last place you sensed it, but it was able to Sneak away. Or you might think a creature can’t see you in the dark, but it has darkvision. You can attempt to avoid detection by using the Stealth skill to Avoid Notice, Hide, or Sneak, or by using Deception to Create a Diversion.

Observed

In most circumstances, you can sense creatures without difficulty and target them normally. Creatures in this state are observed. Observing requires a precise sense, which for most creatures means sight. If you can’t observe the creature, it’s either hidden, undetected, or unnoticed, and you’ll need to factor in the targeting restrictions. Even if a creature is observed, it might still be concealed.

Hidden

A creature that’s hidden is only barely perceptible. You know what space it occupies, but little else. Perhaps the creature just moved behind cover and successfully used the Hide action. Your target might be behind a waterfall, where you can see some movement but can’t determine an exact location. Maybe you’ve been blinded or the creature is invisible, but you used the Seek basic action to determine its general location based on hearing alone. Regardless of the specifics, you’re off-guard to a hidden creature. When targeting a hidden creature, before you roll to determine your effect, you must attempt a DC 11 flat check. If you fail, you don’t affect the creature, though the actions you used are still expended—as well as any spell slots, costs, and other resources. You remain off-guard to the creature, whether you successfully target it or not.

Undetected

If a creature is undetected, you don’t know what space it occupies, you’re off-guard to it, and you can’t easily target it. Using the Seek basic action can help you find an undetected creature, usually making it hidden from you instead of undetected. If a creature is undetected, that doesn’t necessarily mean you’re unaware of its presence— you might suspect an undetected creature is in the room with you, even though you’re unable to find its space. The unnoticed condition covers creatures you’re unaware of. Targeting an undetected creature is difficult. If you suspect there’s a creature around, you can pick a square and attempt an attack. This works like targeting a hidden creature, but the flat check and attack roll are both rolled in secret by the GM. The GM won’t tell you why you missed—whether it was due to failing the flat check, rolling an insufficient attack roll, or choosing the wrong square. The GM might allow you to try targeting an undetected creature with some spells or other abilities in a similar fashion. Undetected creatures are subject to area effects normally. For instance, suppose an enemy elf wizard cast invisibility and then Sneaked away. You suspect that with the elf’s Speed of 30 feet, they probably moved 15 feet toward an open door. You move up and attack a space 15 feet from where the elf started and directly on the path to the door. The GM secretly rolls an attack roll and flat check, but they know that you were not quite correct—the elf was actually in the adjacent space! The GM tells you that you missed, so you decide to make your next attack on the adjacent space, just in case. This time, it’s the right space, and the GM’s secret attack roll and flat check both succeed, so you hit!

Unnoticed

If you have no idea a creature is even present, that creature is unnoticed by you. A creature that is undetected might also be unnoticed. This condition usually matters for abilities that can be used only against targets totally unaware of your presence.

Concealed

A concealed creature is in mist, within dim light, or amid something else that obscures sight but isn’t a physical barrier. When you target a creature that’s concealed from you, you must attempt a DC 5 flat check before you roll to determine your effect. If you fail, you don’t affect the target. The concealed condition doesn’t change which of the main categories of detection apply. A creature in a light fog bank is still observed even though it’s concealed.

Invisible

A creature with the invisible condition (by way of an invisibility spell, for example) is automatically undetected to any creatures relying on sight as their only precise sense. Precise senses other than sight ignore the invisible condition. You can Seek to attempt to figure out an invisible creature’s location, making it only hidden from you. This lasts until the invisible creature successfully uses Sneak to become undetected again. If you’re already observing a creature when it becomes invisible, it starts out hidden, since you know where it was, though it can then Sneak to become undetected. Other effects might partially foil invisibility. For instance, if you were tracking an invisible creature’s footprints through the snow, the footprints would make it hidden. Throwing a net over an invisible creature would make it observed but concealed for as long as the net is on it.

Detecting with Other Senses

Most abilities that designate “a creature you can see” or the like function just as well if the user can precisely sense the subject with a different sense. If a monster uses a sense other than vision, the GM can adapt ways of avoiding detection that work with the monster’s senses. For example, a creature that has echolocation might use hearing as a primary sense. This could mean its quarry is concealed in a noisy chamber, hidden in a great enough din, or invisible under a silence spell.

Using Stealth with Other Senses

The Stealth skill is designed to use Hide for avoiding visual detection and Avoid Notice and Sneak to avoid being both seen and heard. For many special senses, a player can describe how they’re avoiding detection by that special sense and use the most applicable Stealth action. For instance, a creature stepping lightly to avoid being detected via tremorsense would be using Sneak.

In some cases, rolling a Dexterity-based Stealth skill check to Sneak doesn’t make the most sense. For example, a PC trying to avoid being detected by a creature that senses heartbeats might meditate to slow their heart rate, using Wisdom instead of Dexterity for their Stealth check. When a creature could detect you using multiple different senses, use your lowest applicable attribute modifier.