| Document and Entity Information | Jan. 19, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Jan. 19, 2022 |
| Entity Registrant Name | CASPER SLEEP INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-39214 |
| Entity Tax Identification Number | 46-3987647 |
| Entity Address, Address Line One | Three World Trade Center |
| Entity Address, Address Line Two | 175 Greenwich Street, Floor 40 |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10007 |
| City Area Code | 347 |
| Local Phone Number | 941-1871 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Entity Central Index Key | 0001598674 |
| Title of 12(b) Security | Common Stock, par value $0.000001 per share |
| Trading Symbol | CSPR |
| Security Exchange Name | NYSE |
