Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Jul. 31, 2020
Document and Entity Information [Abstract]
Entity Registrant Name	CYREN Ltd.
Entity Central Index Key	0001084577
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Type	10-Q
Document Period End Date	Jun. 30, 2020
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2020
Entity Filer Category	Non-accelerated Filer
Entity Current Reporting Status	Yes
Entity Small Business	true
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		60,413,557
Entity File Number	000-26495
Entity Interactive Data Current	Yes
Entity Incorporation State Country Code	L3