Cover Page - shares	3 Months Ended
	Jun. 30, 2019	Jul. 24, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
Document Transition Report	false
Entity File Number	000-21783
Entity Registrant Name	8X8 INC /DE/
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	77-0142404
Entity Address, Address Line One	2125 O'Nel Drive
Entity Address, City or Town	San Jose
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95131
City Area Code	408
Local Phone Number	727-1885
Title of 12(b) Security	COMMON STOCK, PAR VALUE $.001 PER SHARE
Trading Symbol	EGHT
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		99,287,508
Entity Central Index Key	0001023731
Amendment Flag	false
Current Fiscal Year End Date	--03-31
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2020