Below are the Exploits available to Barbarians. If an Exploit has a prerequisite, like a minimum Ability Score or level, you can learn it at the same time you meet the prerequisites.
1st-Degree Exploits
Exploits of the 1st-degree are minor techniques slightly more complicated than swinging a weapon. They can be learned by warriors with modest training and have no level prerequisite.
2nd-Degree Exploits
Exploits of the 2nd-degree represent the peak of martial skill and ability achievable by warriors without dedicated training. These can be learned by any Barbarian of 5th level or higher.
3rd-Degree Exploits
3rd-degree Exploits are feats of savagery, and can be learned by Barbarians of 9th level or higher. Each 3rd-degree Exploit you know can only be used once per short or long rest.
4th-Degree Exploits
Exploits of this degree can only be learned by Barbarians of 13th level or higher, and each 4th-degree Exploit that you know can only be used once per short or long rest.
5th-Degree Exploits
Exploits of the 5th degree are primal feats that rival legendary monsters. These Exploits can only be learned by Barbarians of 17th level or higher. Each 5th-degree Exploit that you know can only be used once per long rest.