| Document and Entity Information | Jul. 29, 2020 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0000105319 |
| Current Fiscal Year End Date | --01-02 |
| Document Type | 8-K |
| Document Period End Date | Jul. 29, 2020 |
| Entity Registrant Name | WW INTERNATIONAL, INC. |
| Entity Incorporation State Country Code | VA |
| Entity File Number | 001-16769 |
| Entity Tax Identification Number | 11-6040273 |
| Entity Address, Address Line One | 675 Avenue of the Americas |
| Entity Address, Address Line Two | 6th Floor |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10010 |
| City Area Code | (212) |
| Local Phone Number | 589-2700 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, no par value |
| Trading Symbol | WW |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
