Probe-based qPCR (quantitative polymerase chain reaction) is a technique used to quantify multiple targets in a single reaction by using a unique fluorescent dye for each amplicon-specific probe.

The principle of probe-based qPCR is based on hydrolysis of a fluorescently-tagged probe to detect complementary strand extension in real time. The probe binds to a specific location on the target DNA sequence and emits fluorescence when cleaved by the Taq polymerase during amplification. The amount of fluorescence generated is directly proportional to the amount of target DNA present in the sample, allowing for real-time quantification of DNA.