Cover Page - shares	3 Months Ended
	Mar. 31, 2021	May 05, 2021
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	001-39747
Entity Registrant Name	SEER, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-1153150
Entity Address, Address Line One	3800 Bridge Parkway
Entity Address, Address Line Two	Suite 102
Entity Address, City or Town	Redwood City
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94065
City Area Code	650
Local Phone Number	453-0000
Title of 12(b) Security	Common Stock, par value $0.00001
Trading Symbol	SEER
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Shell Company	false
Entity Central Index Key	0001726445
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Ex Transition Period	false
Class A common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		56,630,310
Class B common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		4,702,381