Note 1 - Business and Organization (Details Textual)	3 Months Ended						9 Months Ended
	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)	Sep. 30, 2017
Number of Wholly-Owned Subsidiaries	6						6
Revenue from Contract with Customer, Including Assessed Tax	$ 2,672,000			$ 1,500,000			$ 7,860,000	$ 3,786,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(1,508,000)	$ (1,626,000)	$ (494,000)	(847,000)	$ (1,333,000)	$ (1,544,000)	(3,628,000)	(3,724,000)
Net Cash Provided by (Used in) Operating Activities							(2,363,000)	$ (2,803,000)
Working Capital (Deficit)	2,951,000						2,951,000
Assets, Current	4,691,000						4,691,000		$ 3,153,000
Stock Issued During Period, Value, New Issues	203,000	494,000	800,000	$ 1,117,000	$ 948,000	$ 1,202,000
Cash and Cash Equivalents, at Carrying Value	3,042,000						3,042,000		$ 1,851,000
Vehicle Loan [Member]
Long-Term Debt	71,000						71,000
SBA CARES Act Paycheck Protection Program [Member]
Long-Term Debt	140,000						140,000
Economic Injury Disaster Loan [Member]
Long-Term Debt	148,000						148,000
Inventory Line of Credit [Member] | Clyra Medical Technologies [Member]
Long-Term Line of Credit	$ 234,000						234,000
The 2020 Unit Offering [Member]
Stock Issued During Period, Value, New Issues							995,000
Lincoln Park Capital Fund, LLC [Member]
Stock Issued During Period, Value, New Issues							$ 502,000
Clyra Medical Technologies [Member]
Subsidiary, Ownership Percentage, Parent	53.00%						53.00%
Noncontrolling Interest, Increase from Subsidiary Equity Issuance	$ 288,000	$ 1,062,000	225,000				$ 1,575,000
BioLargo Engineering, Science & Technologies, LLC [Member]
Subsidiary, Ownership Percentage, Parent										100.00%
BioLargo Engineering, Science & Technologies, LLC [Member] | Approximation [Member]
Subsidiary, Ownership Percentage, Parent	82.00%						82.00%
BioLargo Energy Technologies, Inc (BETI) [Member]
Subsidiary, Ownership Percentage, Parent	96.00%						96.00%
Noncontrolling Interest, Increase from Subsidiary Equity Issuance			$ 550,000				$ 905,000