Robotics topped online staffing provider Upwork’s third-quarter list of 20 fastest-growing skills for freelancers. It was followed by blockchain and bitcoin skills in the No. 2 and No. 3 slots.

It was the first time robotics ranked as the fastest-growing skill, and it was the first time blockchain and bitcoin appeared on the fastest-growing list. Bitcoin is a cryptocurrency supported by blockchain, a distributed ledger technology.

The skills categories on the list in the third quarter all experienced more than 100% year-over-year growth; the top 10 grew more than 200%.

The top 20 fastest-growing skills:

1. Robotics
2. Blockchain
3. Bitcoin
4. Penetration testing
5. React.js
6. Amazon Web Services Lambda
7. Augmented reality
8. Deep learning
9. Instagram marketing
10. Final Cut Pro X
11. Swift development
12. AngularJS development
13. Salesforce
14. Vulnerability assessment
15. Natural language processing
16. HubSpot marketing
17. Machine learning
18. Objective-C development
19. Learning Management System (LMS)
20. jQuery development