| Cover | Mar. 30, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Mar. 30, 2022 |
| Entity Registrant Name | Expensify, Inc. |
| Entity Incorporation, State | DE |
| Entity File Number | 001-41043 |
| Entity Tax Identification Number | 27-0239450 |
| Entity Address, Street | 401 SW 5th Ave |
| Entity Address, City | Portland |
| Entity Address, State | OR |
| Entity Address, Postal Zip Code | 97204 |
| City Area Code | 971 |
| Local Phone Number | 365-3939 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of each class | Class A Common Stock, par value $0.0001 per share |
| Trading Symbols | EXFY |
| Name of each exchange on which registered | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Entity Central Index Key | 0001476840 |
| Amendment Flag | false |
