X-box binding protein 1 (XBP1) is a transcription factor that plays a central role in the unfolded protein response, a cellular stress response to the accumulation of misfolded proteins in the endoplasmic reticulum. The XBP1 luciferase reporter vector is designed to study the transcriptional activity of XBP1. The vector contains a XBP1 DNA consensus binding site and TA minimal promoter upstream of a firefly luciferase reporter gene, which can specifically report XBP1 activity while maintaining a low basal level of transcription.