Note 8 - Noncontrolling Interest - Clyra Medical (Details Textual) - USD ($)				3 Months Ended			6 Months Ended		12 Months Ended
	Dec. 20, 2022	Mar. 02, 2022	Jun. 30, 2020	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022	Apr. 08, 2022
Preferred Stock, Shares Outstanding (in shares)				0			0		0
Proceeds from Issuance of Preferred Stock and Preference Stock							$ 1,287,000	$ 0
Clyra Medical [Member]
Shares, Outstanding (in shares)				95,301			95,301		91,145
Common Stock, Shares, Outstanding (in shares)				89,070			89,070		89,070
Shares Issued, Price Per Share (in dollars per share)	$ 310
Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price (in dollars per share)							$ 146.06	$ 1.00
Clyra Medical [Member] | Vendors and Employees [Member] | Share-Based Payment Arrangement, Option [Member]
Share-Based Payment Arrangement, Expense				$ 66,000		$ 82,000	$ 127,000	$ 223,000
Clyra Medical [Member] | Employees and Consultants [Member] | Share-Based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Discount Rate							30.00%
Clyra Medical [Member] | Employees and Consultants [Member] | The Remaining Options [Member]
Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price (in dollars per share)							$ 310
Clyra Medical [Member] | Warrants Issued in Conjunction With the Sale of Series A Preferred Stock [Member]
Warrants and Rights Outstanding, Term (Year)	3 years
Warrants and Rights Outstanding				$ 324,000			$ 324,000
Clyra Medical [Member] | Shares Issued for Debt Owed to Biolargo [Member]
Debt Conversion, Converted Instrument, Amount		$ 633,000
Debt Conversion, Converted Instrument, Shares Issued (in shares)		2,042
Clyra Medical [Member] | Series A Preferred Stock [Member]
Preferred Stock, Shares Outstanding (in shares)				6,231			6,231		2,075
Stock Issued During Period, Shares, New Issues (in shares)				3,427			4,879
Proceeds from Issuance of Preferred Stock and Preference Stock				$ 1,062,000			$ 1,287,000
Shares Issued, Price Per Share (in dollars per share)	$ 372
Preferred Stock, Dividend Rate, Percentage	15.00%
Preferred Stock, Convertible, Sale of Stock Amount	$ 5,000,000
Clyra Medical [Member] | Revolving Credit Facility [Member] | Vernal Bay Capital Group, LLC [Member] | Inventory Line of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity			$ 1,000,000
Proceeds from Lines of Credit, Total			260,000
Repayments of Lines of Credit			$ 117,000
Stock Issued During Period, Shares, Commitment Fee (in shares)			322						322
Stock Issued During Period, Value, Commitment Fee			$ 70,000
Debt Instrument, Percentage of Principal Payment, Cap									15.00%
Long-Term Line of Credit				$ 143,000			$ 143,000		$ 161,000
Clyra Medical [Member] | Notes Payable, Other Payables [Member]
Debt Instrument, Face Amount										$ 100,000
Debt Instrument, Interest Rate, Stated Percentage										8.00%
Debt Instrument, Convertible, Sale of Stock Amount										$ 5,000,000
Debt Instrument, Convertible, Conversion Percentage										70.00%
Vernal Bay Capital Group, LLC [Member] | Conversion of Clyra Medical Stock Into Biolargo Common Stock [Member]
Conversion of Stock, Shares Issued (in shares)					527,983
Clyra Medical Technologies [Member]
Noncontrolling Interest, Ownership Percentage by Parent				56.00%			56.00%
Clyra Medical [Member] | Common Stock [Member]
Investment Owned, Balance, Shares (in shares)				51,571			51,571		51,571
Clyra Medical [Member] | Preferred Stock, Series A [Member]
Investment Owned, Balance, Shares (in shares)				1,352			1,352		1,352