Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2023	Oct. 31, 2023
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Entity Registrant Name	EngageSmart, Inc.
Entity Central Index Key	0001863105
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		168,096,841
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity File Number	001-40835
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	83-2785225
Entity Address, Address Line One	30 Braintree Hill Office Park
Entity Address, Address Line Two	Suite 101
Entity Address, City or Town	Braintree
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02184
City Area Code	781
Local Phone Number	848-3733
Document Quarterly Report	true
Document Transition Report	false
Security 12b Title	Common stock, $0.001 par value per share
Trading Symbol	ESMT
Security Exchange Name	NYSE