Document and Entity Information - USD ($)	12 Months Ended
	Dec. 28, 2019	Feb. 01, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 28, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Trading Symbol	WW
Entity Registrant Name	WW INTERNATIONAL, INC.
Entity Central Index Key	0000105319
Current Fiscal Year End Date	--12-28
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		67,427,547
Entity Public Float			$ 889,175,384
Entity File Number	001-16769
Entity Incorporation, State or Country Code	VA
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
Title of 12(b) Security	Common Stock, no par value
Security Exchange Name	NASDAQ
Entity Interactive Data Current	Yes
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	Portions of the registrant’s definitive Proxy Statement for its 2020 annual meeting of shareholders are incorporated herein by reference in Part III, Items 10-14. Such Proxy Statement will be filed with the SEC no later than 120 days after the registrant’s fiscal year ended December 28, 2019.