Cover - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Apr. 01, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2023
Current Fiscal Year End Date	--12-31
Entity File Number	333-193087
Entity Registrant Name	FOCUS UNIVERSAL INC.
Entity Central Index Key	0001590418
Entity Tax Identification Number	46-3355876
Entity Incorporation, State or Country Code	NV
Entity Address, Address Line One	2311 East Locust Court
Entity Address, City or Town	Ontario
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	91761
City Area Code	(626)
Local Phone Number	272-3883
Title of 12(b) Security	Common Stock, $0.001 par value
Trading Symbol	FCUV
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float				$ 47,304,201
Entity Public Float			64,771,817
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Auditor Firm ID	572	6906
Auditor Name	Weinberg & Company, P.A.	Reliant CPA PC
Auditor Location	Los Angeles, CA.	Newport Beach, CA