Note 8 - Noncontrolling Interest - Clyra Medical (Details Textual) - USD ($)							1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
		Jun. 30, 2023	Jan. 09, 2023	Dec. 20, 2022	Mar. 02, 2022	Jun. 30, 2020	Jul. 31, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 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										$ 1,575,000	$ 100,000
Warrants and Rights Outstanding	[1]							$ 18,000		18,000
Proceeds from Stock Options Exercised										$ 3,000	$ 0
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)								1,660		1,660		1,352
Clyra Medical [Member]
Shares, Outstanding (in shares)								99,501		99,501		91,145
Common Stock, Shares, Outstanding (in shares)								92,035		92,035		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)										$ 171.99	$ 1
Proceeds from Stock Options Exercised								$ 2,964
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period (in shares)								2,964		2,964
Clyra Medical [Member] | Vendors and Employees [Member] | Share-Based Payment Arrangement, Option [Member]
Share-Based Payment Arrangement, Expense								$ 45,000	$ 85,000	$ 172,000	$ 308,000
Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price (in dollars per share)										$ 271
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] | Warrants Issued in Conjunction With the Sale of Series A Preferred Stock [Member]
Warrants and Rights Outstanding, Term (Month)				3 years
Warrants and Rights Outstanding				$ 410,000
Clyra Medical [Member] | Shares Issued for Debt Owed to Biolargo [Member]
Debt Conversion, Converted Instrument, Amount					$ 633,000		$ 96,000
Debt Conversion, Converted Instrument, Shares Issued (in shares)					2,042		308
Clyra Medical [Member] | Series A Preferred Stock [Member]
Preferred Stock, Shares Outstanding (in shares)								7,466		7,466		2,075
Stock Issued During Period, Shares, New Issues (in shares)								928		5,081
Proceeds from Issuance of Preferred Stock and Preference Stock								$ 288,000		$ 1,575,000
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		$ 126,000
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								$ 134,000		$ 134,000		$ 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

[1] Aggregate intrinsic value based on closing common stock price of $0.17 at September 30, 2023.