| Cover | Aug. 30, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 30, 2021 |
| Entity File Number | 000-55247 |
| 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 Street |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock, $0.001 par value per share |
| Trading Symbol | FCUV |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Elected Not To Use the Extended Transition Period | false |
