Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit) - USD ($)	Common Stock IPO	Common Stock	Additional Paid-in capital IPO	Additional Paid-in capital	Accumulated other comprehensive loss	Accumulated deficit	Series A convertible preferred stock	Series B convertible preferred stock	Series C convertible preferred stock	IPO	Total
Temporary equity, beginning balance at Dec. 31, 2016							$ 6,483,044	$ 26,399,079
Temporary Equity, Beginning Balance (in shares) at Dec. 31, 2016							612,446	3,913,207
Increase (Decrease) in Temporary Equity
Issuance of convertible preferred stock, net of issuance costs								$ 23,343,863
Issuance of convertible preferred stock (in shares)								3,322,762
Temporary equity, ending balance at Dec. 31, 2017							$ 6,483,044	$ 49,742,942
Temporary Equity, Ending Balance (in shares) at Dec. 31, 2017							612,446	7,235,969
Equity, beginning balance at Dec. 31, 2016		$ 126,838		$ 18,940,120	$ (8,782,566)	$ (31,749,937)					$ (21,465,545)
Equity, Beginning Balance (in shares) at Dec. 31, 2016		1,153,061
Increase (Decrease) in Stockholders' Equity
Stock based compensation				395,440							395,440
Foreign currency translation					495,160						495,160
Net loss						(15,190,250)					(15,190,250)
Equity, ending balance at Dec. 31, 2017		$ 126,838		19,335,560	(8,287,406)	(46,940,187)					(35,765,195)
Equity, Ending Balance (in shares) at Dec. 31, 2017		1,153,061
Increase (Decrease) in Temporary Equity
Issuance of convertible preferred stock, net of issuance costs									$ 56,364,645
Issuance of convertible preferred stock (in shares)									4,712,698
Temporary equity, ending balance at Dec. 31, 2018							$ 6,483,044	$ 49,742,942	$ 56,364,645
Temporary Equity, Ending Balance (in shares) at Dec. 31, 2018							612,446	7,235,969	4,712,698
Increase (Decrease) in Stockholders' Equity
Exercise of stock options		$ 253		1,844							$ 2,097
Exercise of stock options (in shares)		2,305									2,306
Stock based compensation				329,184							$ 329,184
Foreign currency translation					(473,919)						(473,919)
Net loss						(15,528,269)					(15,528,269)
Equity, ending balance at Dec. 31, 2018		$ 127,091		19,666,588	(8,761,325)	(62,468,456)					(51,436,102)
Equity, Ending Balance (in shares) at Dec. 31, 2018		1,155,366
Increase (Decrease) in Temporary Equity
Issuance of convertible preferred stock, net of issuance costs									$ 5,598,362
Issuance of convertible preferred stock (in shares)									467,179
Exchange and conversion of preferred stock and common stock of Aprea Therapeutics AB into common stock of Aprea Therapeutics Inc		$ (128,792)		128,792
Temporary Equity, Ending Balance (in shares) at Dec. 31, 2019							0	0	0
Increase (Decrease) in Stockholders' Equity
Exercise of stock options		$ 3,179		67,818							$ 70,997
Exercise of stock options (in shares)		322,267									322,267
Issuance of common stock	$ 6,517		$ 86,899,563	100						$ 86,906,080	$ 100
Issuance of common stock (in shares)	6,516,667	160
Stock based compensation				1,345,722							1,345,722
Foreign currency translation					(2,772,453)						(2,772,453)
Conversion of preferred stock into common stock		$ 13,028		118,175,965			$ (6,483,044)	$ (49,742,942)	$ (61,963,007)		118,188,993
Conversion of preferred stock into common stock (in shares)		13,028,292					(612,446)	(7,235,969)	(5,179,877)
Net loss						(28,059,807)					(28,059,807)
Equity, ending balance at Dec. 31, 2019		$ 21,023		$ 226,284,548	$ (11,533,778)	$ (90,528,263)					$ 124,243,530
Equity, Ending Balance (in shares) at Dec. 31, 2019		21,022,752