UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Statement [Abstract]
Revenue	$ 97,410,000	$ 78,718,000	$ 274,173,000	$ 224,281,000
Cost of revenue	17,063,000	13,032,000	46,665,000	38,643,000
Gross profit	80,347,000	65,686,000	227,508,000	185,638,000
Operating expenses
Sales and marketing	35,689,000	30,094,000	104,610,000	95,827,000
Research and development	22,183,000	14,075,000	58,775,000	42,071,000
General and administrative	20,770,000	18,769,000	57,556,000	56,797,000
Exit costs	0	0	0	1,292,000
Total operating expenses	78,642,000	62,938,000	220,941,000	195,987,000
Income (loss) from operations	1,705,000	2,748,000	6,567,000	(10,349,000)
Other income, net	2,912,000	2,104,000	9,167,000	6,728,000
Income (loss) before income taxes	4,617,000	4,852,000	15,734,000	(3,621,000)
Provision for income taxes	3,899,000	637,000	11,652,000	2,303,000
Net income (loss)	718,000	4,215,000	4,082,000	(5,924,000)
Net loss attributable to noncontrolling interest in consolidated subsidiaries	(376,000)	0	(809,000)	0
Net income (loss) attributable to Semrush Holdings, Inc.	$ 1,094,000	$ 4,215,000	$ 4,891,000	$ (5,924,000)
Net income (loss) per share attributable to common stockholders
Net income (loss) attributable to Semrush Holdings, Inc. per share attributable to common stockholders—basic (in dollars per share)	$ 0.01	$ 0.03	$ 0.03	$ (0.04)
Net income (loss) attributable to Semrush Holdings, Inc. per share attributable to common stockholders—diluted (in dollars per share)	$ 0.01	$ 0.03	$ 0.03	$ (0.04)
Weighted-average number of shares of common stock used in computing net income (loss) per share attributable to common stockholders
Weighted-average number of shares of common stock used in computing net income (loss) per share attributable to common stockholders—basic (in shares)	146,436,167	142,837,120	145,563,220	142,246,586
Weighted-average number of shares of common stock used in computing net income (loss) per share attributable to common stockholders—diluted (in shares)	149,426,665	146,270,628	148,653,023	142,246,586
Comprehensive income (loss)
Net income (loss)	$ 718,000	$ 4,215,000	$ 4,082,000	$ (5,924,000)
Other comprehensive income (loss):
Foreign currency translation adjustments	1,358,000	(51,000)	754,000	193,000
Unrealized gain (loss) on investments	2,626,000	64,000	1,698,000	(1,179,000)
Comprehensive income (loss)	4,702,000	4,228,000	6,534,000	(6,910,000)
Comprehensive loss attributable to noncontrolling interest in consolidated subsidiaries	(376,000)	0	(809,000)	0
Comprehensive income (loss) attributable to Semrush Holdings, Inc.	$ 5,078,000	$ 4,228,000	$ 7,343,000	$ (6,910,000)