Cover - shares	9 Months Ended
	Sep. 30, 2024	Nov. 01, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2024
Document Transition Report	false
Entity File Number	001-41781
Entity Registrant Name	SEZZLE INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-0971660
Entity Address, Address Line One	700 Nicollet Mall
Entity Address, Address Line Two	Suite 640
Entity Address, City or Town	Minneapolis
Entity Address, State or Province	MN
Entity Address, Postal Zip Code	55402
Country Region	+1
City Area Code	651
Local Phone Number	240 6001
Title of 12(b) Security	Common Stock, par value $0.00001 per share
Trading Symbol	SEZL
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		5,607,034
Entity CIK	0001662991
Amendment flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31