| Document and Entity Information | May 05, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | May 5, 2021 |
| Entity Registrant Name | LESLIE’S, INC. |
| Entity Central Index Key | 0001821806 |
| Entity Emerging Growth Company | false |
| Entity File Number | 001-39667 |
| Entity Incorporation State Country Code | DE |
| Entity Tax Identification Number | 20-8397425 |
| Entity Address Address Line1 | 2005 East Indian School Road |
| Entity Address City Or Town | Phoenix |
| Entity Address State Or Province | AZ |
| Entity Address Postal Zip Code | 85016 |
| City Area Code | (602) |
| Local Phone Number | 366-3999 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security12b Title | Common Stock, par value $0.001 per share |
| Trading Symbol | LESL |
| Security Exchange Name | NASDAQ |
