CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Income Statement [Abstract]
Revenue	$ 159,624	$ 73,012	$ 401,584	$ 177,056
Cost of revenue	66,681	29,489	159,684	82,035
Gross profit	92,943	43,523	241,900	95,021
Sales and marketing	134,727	75,668	325,267	213,133
Research and development	74,138	27,669	143,949	75,451
General and administrative	53,532	30,318	116,224	79,413
Total operating expenses	262,397	133,655	585,440	367,997
Operating loss	(169,454)	(90,132)	(343,540)	(272,976)
Interest income	1,517	2,491	5,654	9,252
Other expense, net	(519)	(40)	(1,561)	(819)
Loss before income taxes	(168,456)	(87,681)	(339,447)	(264,543)
Provision for income taxes	433	376	720	738
Net loss	$ (168,889)	$ (88,057)	$ (340,167)	$ (265,281)
Net loss per share attributable to Class A and Class B common stockholders - basic and diluted (in dollars per share)	$ (1.01)	$ (1.92)	$ (3.63)	$ (6.15)
Weighted-average shares used in computing net loss per share attributable to Class A and Class B common stockholders - basic and diluted (in shares)	166,868,200	45,911,449	93,763,599	43,113,683