Ki sensing is the ability to sense the location, life force, and power level of anyone, the stronger and closer the enemy, the more powerful the sensation. Also, if one has higher energy, he can sense strong people from afar; like Super Buu sensing Ultimate Gohan's energy. Once a fighter masters the skill, they can use it even when their other five senses are incapacitated.No outsider knows the sensations associated with ki sensing, as Mr. Popo likes explaining it to someone as being like "describing sight to the blind." However, the manga and anime usually show a minor spark on their head to signify that the Z Fighter is picking up a power.
Frieza and his army, who did not possess this ability, use a device called a scouter that can give numerical readings of a person's location and power level. However, scouters have been shown to be very fragile, breaking when a fighter powers up too much, making the ki sensing technique preferred for those who know how to use it.
Namekians are able to sense if the life force is good or evil, such as when the Ginyu Force arrived on Namek. Krillin sensed their presences and thought it was Goku, but Nail said "I, too, sense the presense of evil coming." The Namekian ki sense was first displayed when Raditz approached Piccolo, who reasoned that the incoming power couldn't be Goku because "It's too horrible." Trained Saiyans also have the ability to sense whether or not a presence is good or evil, as Goku said "It's a horrible power, too! I'm trembling!" as he sensed Raditz approaching Kame House.
The Instant Transmission technique, requires the user to home in on a ki signature before teleporting them to that ki signatures location or somewhere nearby. Meaning the ability to sense ki is a requirement (the Instantaneous Movement technique however doesn't require a ki signature or the ability to sense ki).
- Goku first learned the technique after drinking the Ultra Divine Water, but was only able to tell where Piccolo was; after training under Mr. Popo, he was able to master the skill to the point where he was not worried about Tien Shinhan fighting Mercenary Tao, because he knew Tien could beat him.
- At the beginning of Dragonball Z, Krillin had also learned the ability through unknown means, and by the time Vegeta and Nappa had invaded Earth, all of the Z Fighters had learned the skill. Vegeta had also managed to learn this ability after his battle on Earth.
- Mr. Popo helped Goku, Krillin, Tien Shinhan, Yamcha, and Chiaotzu master ki sensing.
- Master Roshi is shown to possess this ability at various points in the series.
- Dr. Wheelo is shown to be able to detect ki. It is unknown if this ability is natural or mechnical or a combination of both.
- Though Frieza and King Cold are unable to sense power levels without a scouter, Cooler can (as it is required to use the Instant Transmission technique) sense power levels as well as hide his own immense power level (allowing him to be able to sneak up opponents like Piccolo). The Meta-Coolers appear to be able to detect power levels likely through technological means.
- Android 19 and Android 20/Dr. Gero are able to detect and analize an opponents power level much like a scouter.
- Android 13, Android 14, and Android 15 all possess ki sensing devices linked to Dr. Gero's Super Computer.
- Androids 17 and 18 could not sense power levels, although Android 16 had software in his design that worked much like a scouter.
- Android 18 may have later learned how to sense ki (maybe from her husband, Krillin ).