Consolidated Statements of Convertible Preference Shares and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	IPO	Class B Convertible Preference Stock	Class C Convertible Preference Stock	Common Stock	Common Stock IPO	Common Stock Class A Ordinary Shares	Additional Paid-In Capital	Additional Paid-In Capital IPO	Other Comprehensive Loss	Accumulated Deficit
Temporary equity, Balance at Dec. 31, 2019			$ 22,060
Temporary equity, Balance, shares at Dec. 31, 2019			366,301
Balance at Dec. 31, 2019	$ (23,531)				$ 0		$ 28	$ 1,504		$ 1,297	$ (26,360)
Balance, shares at Dec. 31, 2019							177,200
Temporary equity, Issuance of preference shares, net of issuance costs			$ 5,573
Temporary equity, Issuance of preference shares, net of issuance costs, shares			75,845
Temporary equity, issuance of shares upon conversion of securities			$ 10,273
Temporary equity, issuance of shares upon conversion of securities, shares			142,437
Issuance of common stock	(458)							(458)
Equity-based compensation expense	64							64
Currency translation	664									664
Net loss	(12,042)										(12,042)
Temporary equity, Balance at Dec. 31, 2020			$ 37,906
Temporary equity, Balance, shares at Dec. 31, 2020			584,583
Balance at Dec. 31, 2020	(35,303)				0		$ 28	1,110		1,961	(38,402)
Balance, shares at Dec. 31, 2020							177,200
Temporary equity, Issuance of class C preference shares, net of issuance costs of $340 and adjusted for settlement of tranche obligation of $28,276 of which $25,908 is non-cash				$ 175,509
Temporary equity, Issuance of class C preference shares, net of issuance costs of $340 and adjusted for fair value of tranche obligation of $25,908 at non-cash settlement, shares				1,194,864
Temporary equity, issuance of shares upon conversion of securities			$ (37,906)	$ (175,509)
Temporary equity, issuance of shares upon conversion of securities, shares			(584,583)	(1,194,864)
Exchange of preferred and ordinary shares of IO Biotech ApS into common stock of IO Biotech, Inc.	213,415				$ 21		$ (28)	213,422
Exchange of preferred and ordinary shares of IO Biotech ApS into common stock of IO Biotech, Inc., shares					20,592,413		(177,200)
Issuance of common stock, shares					354	8,222,500
Issuance of common stock	0	$ 103,350			$ 0	$ 8			$ 103,342
Equity-based compensation expense	1,791							1,791
Currency translation	(3,450)									(3,450)
Net loss	(67,879)										(67,879)
Temporary equity, Balance, shares at Dec. 31, 2021			0
Balance at Dec. 31, 2021	$ 211,924				$ 29			$ 319,665		$ (1,489)	$ (106,281)
Balance, shares at Dec. 31, 2021					28,815,267