| Document And Entity Information | May 17, 2022 |
| Document Information [Line Items] | |
| Entity, Registrant Name | BioLargo, Inc. |
| Document, Type | 8-K |
| Document, Period End Date | May 17, 2022 |
| Entity, Incorporation, State or Country Code | DE |
| Entity, File Number | 000-19709 |
| Entity, Tax Identification Number | 65-0159115 |
| Entity, Address, Address Line One | 14921 Chestnut St. |
| Entity, Address, City or Town | Westminster |
| Entity, Address, State or Province | CA |
| Entity, Address, Postal Zip Code | 92683 |
| City Area Code | 888 |
| Local Phone Number | 400-2863 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | BLGO |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0000880242 |
