Cover Page - shares	6 Months Ended
	Mar. 31, 2020	May 08, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--09-30
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Registrant Name	Twist Bioscience Corp
Entity Central Index Key	0001581280
Entity Shell Company	false
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Security Exchange Name	NASDAQ
Entity Address, State or Province	CA
Title of 12(b) Security	Common Stock
Trading Symbol	TWST
Entity Common Stock, Shares Outstanding		40,978,695
Entity Incorporation, State or Country Code	DE