Regular Expressions retrieve matching strings in your JMeter load test. Learn to script Regular Expressions in Groovy, and become a performance testing pro.
Tokens and session IDs are sent in the request header. This post will review how to extract them in JMeter scripts with the Regular Expression Extractor.
Should you use the Boundary Extractor or the Regular Expression Extractor in your JMeter scripts? This ultimate comparison will give you the info to choose.