CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Underwriters' Option	Follow-on Public Offering	Total Stockholders’ Equity (Deficit) Attributable to Semrush Holdings, Inc.	Total Stockholders’ Equity (Deficit) Attributable to Semrush Holdings, Inc. Underwriters' Option	Total Stockholders’ Equity (Deficit) Attributable to Semrush Holdings, Inc. Follow-on Public Offering	Common Stock	Additional Paid-in Capital	Additional Paid-in Capital Underwriters' Option	Additional Paid-in Capital Follow-on Public Offering	Accumulated Other Comprehensive Loss	Accumulated Deficit	Noncontrolling Interest in Consolidated Subsidiary	Series A	Series A-1	Series B Preferred Stock	Common Class A	Common Class A Common Stock	Common Class A Common Stock Underwriters' Option	Common Class A Common Stock Follow-on Public Offering	Class B Common Stock	Class B Common Stock Common Stock
Beginning balance (in shares) at Dec. 31, 2020														3,379,400	1,837,600
Beginning balance at Dec. 31, 2020														$ 7,789	$ 10,270
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of preferred stock (in shares)														(3,379,400)	(1,837,600)
Conversion of preferred stock														$ (7,789)	$ (10,270)
Ending balance (in shares) at Dec. 31, 2021														0	0
Ending balance at Dec. 31, 2021														$ 0	$ 0
Beginning balance (in shares) at Dec. 31, 2020																4,681,400
Beginning balance (in shares) at Dec. 31, 2020							95,050,041											0				0
Beginning balance at Dec. 31, 2020	$ (6,840)			$ (6,840)			$ 0	$ 4,975			$ 0	$ (35,815)	$ 0			$ 24,000		$ 0				$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of Class B Common Stock to Class A Common Stock (in shares)							29,695,200									4,681,400		17,121,795				17,121,795
Conversion of Class B Common Stock to Class A Common Stock	18,058			18,058				42,058								$ (24,000)
Issuance of Class A Common Stock (in shares)																		10,000,000	719,266	4,000,000
Issuance of Class A Common Stock	126,622	$ 9,245	$ 77,903	126,622	$ 9,245	$ 77,903		126,622	$ 9,245	$ 77,903
Reclassification of Common Stock to Class B Common Stock in connection with the initial public offering (in shares)							124,745,241															124,745,241
Reclassification of Common Stock to Class B Common Stock in connection with the initial public offering	0							(1)														$ 1
Issuance of common stock upon exercise of stock options (in shares)																						1,194,918
Issuance of common stock upon exercise of stock options	1,327			1,327				1,327
Vesting of Class B Common Stock in connection with Restricted Stock (in shares)																						51,762
Stock-based compensation	2,742			2,742				2,742
Cumulative translation adjustment	(230)			(230)							(230)
Unrealized (loss) gain on investments	0
Net income (loss)	(3,285)			(3,285)								(3,285)
Ending balance (in shares) at Dec. 31, 2021																0
Ending balance (in shares) at Dec. 31, 2021							0											31,841,061				108,870,126
Ending balance at Dec. 31, 2021	225,542			225,542			$ 0	264,871			(230)	(39,100)	0			$ 0		$ 0				$ 1
Ending balance (in shares) at Dec. 31, 2022														0	0
Ending balance at Dec. 31, 2022														$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of Class B Common Stock to Class A Common Stock (in shares)																		11,078,315				11,078,315
Issuance of common stock upon exercise of stock options (in shares)																		681,860
Issuance of common stock upon exercise of stock options	981			981				981
Vesting of Class B Common Stock in connection with Restricted Stock (in shares)																		77,182				51,759
Issuance of shares in connection with Employee Stock Purchase Plan (in shares)																		64,756
Issuance of shares in connection with Employee Stock Purchase Plan	758			758				758
Stock-based compensation	7,447			7,447				7,447
Cumulative translation adjustment	(851)			(851)							(851)
Unrealized (loss) gain on investments	(125)			(125)							(125)
Net income (loss)	$ (33,848)			(33,848)								(33,848)
Ending balance (in shares) at Dec. 31, 2022	0															0
Ending balance (in shares) at Dec. 31, 2022							0										43,743,000	43,743,174			97,844,000	97,843,570
Ending balance at Dec. 31, 2022	$ 199,904			199,904			$ 0	274,057			(1,206)	(72,948)	0			$ 0		$ 0				$ 1
Ending balance (in shares) at Dec. 31, 2023														0	0
Ending balance at Dec. 31, 2023														$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of Class B Common Stock to Class A Common Stock (in shares)																		74,414,844				74,414,844
Conversion of Class B Common Stock to Class A Common Stock	$ 0																	$ 1				$ (1)
Issuance of common stock upon exercise of stock options (in shares)	1,917,922																	1,917,922				0
Issuance of common stock upon exercise of stock options	$ 2,240			2,240				2,240
Issuance of shares in connection with Employee Stock Purchase Plan (in shares)																		38,879
Issuance of shares in connection with Employee Stock Purchase Plan	264			264				264
Issuance of common stock upon vesting of restricted stock units (in shares)																		514,328				53,331
Stock-based compensation	15,337			15,337				15,337
Cumulative translation adjustment	451			451							451
Unrealized (loss) gain on investments	3
Net income (loss)	950			950								950
Acquisition of noncontrolling interest (See Note 9)	$ 5,166												5,166
Ending balance (in shares) at Dec. 31, 2023	0															0
Ending balance (in shares) at Dec. 31, 2023							0										120,629,000	120,629,147			23,482,000	23,482,057
Ending balance at Dec. 31, 2023	$ 224,315			$ 219,149			$ 0	$ 291,898			$ (752)	$ (71,998)	$ 5,166			$ 0		$ 1				$ 0