Document And Entity Information - shares	6 Months Ended
	Mar. 31, 2017	May 10, 2017
Document Information [Line Items]
Entity Registrant Name	Bridgeline Digital, Inc.
Entity Central Index Key	0001378590
Trading Symbol	blin
Current Fiscal Year End Date	--09-30
Entity Filer Category	Smaller Reporting Company
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Common Stock, Shares Outstanding (in shares)		20,967,876
Document Type	10-Q
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q2
Amendment Flag	false