| Document and Entity Information | Nov. 09, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Nov. 9, 2021 |
| Entity Registrant Name | EngageSmart, Inc. |
| Entity Central Index Key | 0001863105 |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Title of 12(b) Security | Common stock, $0.001 par value per share |
| Trading Symbol | ESMT |
| Security Exchange Name | NYSE |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
