Net Income (loss) per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Jun. 27, 2025	Jun. 28, 2024	Jun. 30, 2023	Feb. 21, 2025
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares issued (in shares)	146,000			145,000
Par value (in dollars per share)	$ 0.01			$ 0.01
Net Income (Loss)	$ (1,641)	$ (672)	$ (2,143)
Weighted average shares outstanding:
Basic (in shares)	145,000	145,000	145,000
Diluted (in shares)	145,000	145,000	145,000
Net loss per common share:
Basic (in dollars per share)	$ (11.32)	$ (4.63)	$ (14.78)
Diluted (in dollars per share)	$ (11.32)	$ (4.63)	$ (14.78)
Antidilutive weighted-average shares (in shares)	2,000	0	0
Western Digital Corporation
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Percent distribution of shares				80.10%