There are several terms for a person who notices everything, depending on the context and the specific type of observation:
Observant
This is a general term for someone who is attentive to their surroundings and details. They are good at noticing changes, patterns, and subtle cues that others might miss.
Perceptive
This term implies a deeper understanding of what they observe. Perceptive people not only notice details but also grasp their significance and implications.
Attentive
This describes someone who pays close attention to their environment and the people around them. They are actively engaged in their surroundings and readily pick up on details.
Astute
This term suggests sharp intelligence and the ability to make insightful observations. Astute individuals often possess a keen understanding of human behavior and motivations.
Mindful
This term emphasizes a conscious awareness of the present moment and all its details. Mindful people are present in their surroundings and notice things that others might overlook.
Detail-Oriented
This describes someone who focuses on the specifics and nuances of a situation. They are meticulous and thorough in their observations.
The specific term you choose depends on the context and the specific type of observation. For example, you might call someone "observant" if they notice a change in someone's behavior, while you might call someone "astute" if they can accurately predict the outcome of a situation based on their observations.