UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Class A Common Stock	Class B Common Stock	Total Stockholders’ Equity Attributable to Semrush Holdings, Inc.	Common Stock Class A Common Stock	Common Stock Class B Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Noncontrolling Interest
Redeemable Noncontrolling Interest, Beginning balance at Dec. 31, 2023	$ 0
Redeemable Noncontrolling Interest, Ending balance at Mar. 31, 2024	0
Beginning balance (in shares) at Dec. 31, 2023					120,629,147	23,482,057
Beginning balance at Dec. 31, 2023	224,315			$ 219,149	$ 1	$ 0	$ 291,898	$ (752)	$ (71,998)	$ 5,166
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)					469,879
Issuance of common stock upon exercise of stock options	844			844			844
Issuance of common stock upon vesting of restricted stock units (in shares)					145,844
Stock-based compensation expense	5,115			5,115			5,115
Cumulative translation adjustment	(485)			(485)				(485)
Unrealized gain (loss) on investments	(744)			(744)				(744)
Net income (loss)	2,138			2,138					2,138
Net loss attributable to noncontrolling interest	(135)									(135)
Ending balance (in shares) at Mar. 31, 2024					121,244,870	23,482,057
Ending balance at Mar. 31, 2024	231,048			226,017	$ 1	$ 0	297,857	(1,981)	(69,860)	5,031
Redeemable Noncontrolling Interest, Beginning balance at Dec. 31, 2023	0
Redeemable Noncontrolling Interest, Ending balance at Jun. 30, 2024	8,733
Beginning balance (in shares) at Dec. 31, 2023					120,629,147	23,482,057
Beginning balance at Dec. 31, 2023	224,315			219,149	$ 1	$ 0	291,898	(752)	(71,998)	5,166
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative translation adjustment	(604)
Unrealized gain (loss) on investments	(928)
Net income (loss)	3,797
Ending balance (in shares) at Jun. 30, 2024					123,061,442	23,072,256
Ending balance at Jun. 30, 2024	240,422			235,619	$ 1	$ 0	306,103	(2,284)	(68,201)	4,803
Redeemable Noncontrolling Interest, Beginning balance at Mar. 31, 2024	0
Increase (Decrease) in Temporary Equity [Roll Forward]
Acquisition of redeemable noncontrolling interest (See Note 9)	9,846
Net loss attributable to redeemable noncontrolling interest	(70)
Reclassification for Tender Offer obligations (See Note 9)	(2,021)
Recording of redeemable noncontrolling interest at redemption value (See Note 9)	978
Redeemable Noncontrolling Interest, Ending balance at Jun. 30, 2024	8,733
Beginning balance (in shares) at Mar. 31, 2024					121,244,870	23,482,057
Beginning balance at Mar. 31, 2024	231,048			226,017	$ 1	$ 0	297,857	(1,981)	(69,860)	5,031
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of Class B Common Stock to Class A Common Stock (in shares)					409,801	409,801
Issuance of common stock upon exercise of stock options (in shares)					720,880
Issuance of common stock upon exercise of stock options	2,209			2,209			2,209
Issuance of common stock upon vesting of restricted stock units (in shares)					685,891
Stock-based compensation expense	7,015			7,015			7,015
Cumulative translation adjustment	(119)			(119)				(119)
Unrealized gain (loss) on investments	(184)			(184)				(184)
Net income (loss)	1,659			1,659					1,659
Net loss attributable to noncontrolling interest	(228)									(228)
Recording of redeemable noncontrolling interest at redemption value (See Note 9)	(978)			(978)			(978)
Ending balance (in shares) at Jun. 30, 2024					123,061,442	23,072,256
Ending balance at Jun. 30, 2024	240,422			235,619	$ 1	$ 0	306,103	(2,284)	(68,201)	4,803
Beginning balance (in shares) at Dec. 31, 2024		125,834,000	21,009,000		125,833,872	21,009,210
Beginning balance at Dec. 31, 2024	266,352			256,604	$ 1	$ 0	322,586	(2,221)	(63,762)	9,748
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of Class B Common Stock to Class A Common Stock (in shares)					100,800	100,800
Issuance of common stock upon exercise of stock options (in shares)					52,666	111,408
Issuance of common stock upon exercise of stock options	365			365			365
Issuance of common stock upon vesting of restricted stock units (in shares)					643,823
Stock-based compensation expense	8,966			8,966			8,966
Cumulative translation adjustment	1,320			1,320				1,320
Unrealized gain (loss) on investments	590			590				590
Net income (loss)	849			849					849
Net loss attributable to noncontrolling interest	(194)									(194)
Acquisition of additional noncontrolling shares	(90)									(90)
Ending balance (in shares) at Mar. 31, 2025					126,631,161	21,019,818
Ending balance at Mar. 31, 2025	278,158			268,694	$ 1	$ 0	331,917	(311)	(62,913)	9,464
Beginning balance (in shares) at Dec. 31, 2024		125,834,000	21,009,000		125,833,872	21,009,210
Beginning balance at Dec. 31, 2024	266,352			256,604	$ 1	$ 0	322,586	(2,221)	(63,762)	9,748
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of Class B Common Stock to Class A Common Stock (in shares)					100,800
Cumulative translation adjustment	4,370
Unrealized gain (loss) on investments	713
Net income (loss)	(5,718)
Ending balance (in shares) at Jun. 30, 2025		127,472,000	21,020,000		127,472,329	21,019,818
Ending balance at Jun. 30, 2025	288,167			279,047	$ 1	$ 0	345,664	2,862	(69,480)	9,120
Beginning balance (in shares) at Mar. 31, 2025					126,631,161	21,019,818
Beginning balance at Mar. 31, 2025	278,158			268,694	$ 1	$ 0	331,917	(311)	(62,913)	9,464
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of Class B Common Stock to Class A Common Stock (in shares)					0
Issuance of common stock upon exercise of stock options (in shares)					114,295
Issuance of common stock upon exercise of stock options	283			283			283
Issuance of common stock upon vesting of restricted stock units (in shares)					726,873
Issuance of common stock upon vesting of restricted stock units	(426)			(426)			(426)
Stock-based compensation expense	13,342			13,342			13,342
Reclassification of liability-classified awards to equity-classified awards	548			548			548
Cumulative translation adjustment	3,050			3,050				3,050
Unrealized gain (loss) on investments	123			123				123
Net income (loss)	(6,567)			(6,567)					(6,567)
Net loss attributable to noncontrolling interest	(210)									(210)
Acquisition of additional noncontrolling shares	(134)									(134)
Ending balance (in shares) at Jun. 30, 2025		127,472,000	21,020,000		127,472,329	21,019,818
Ending balance at Jun. 30, 2025	$ 288,167			$ 279,047	$ 1	$ 0	$ 345,664	$ 2,862	$ (69,480)	$ 9,120