Document and Entity Information - shares
6 Months Ended
Dec. 31, 2015
Jan. 31, 2016
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Dec. 31, 2015  
Document Fiscal Year Focus 2016  
Document Fiscal Period Focus Q2  
Trading Symbol QNST  
Entity Registrant Name QUINSTREET, INC  
Entity Central Index Key 0001117297  
Current Fiscal Year End Date --06-30  
Entity Filer Category Accelerated Filer  
Entity Common Stock, Shares Outstanding   45,233,509