Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2025	May 02, 2025
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2025
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Registrant Name	AMPLITUDE, INC.
Entity Central Index Key	0001866692
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Class A Common Stock, $0.00001 par value per share
Trading Symbol	AMPL
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Incorporation, State or Country Code	DE
Entity File Number	001-40817
Entity Tax Identification Number	45-3937349
Entity Address, Address Line One	201 Third Street
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94103
City Area Code	415
Local Phone Number	231-2353
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		98,795,586
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		32,093,043