Note 8 - Noncontrolling Interest - Clyra Medical (Details Textual)					1 Months Ended		3 Months Ended				6 Months Ended		12 Months Ended		60 Months Ended
		Dec. 04, 2024 USD ($)	Jan. 09, 2023 shares	Jun. 30, 2020 USD ($) shares	Jun. 30, 2024 USD ($) $ / shares shares	Oct. 31, 2023 USD ($) $ / shares shares	Jun. 30, 2025 USD ($) $ / shares shares	Mar. 31, 2025 USD ($)	Jun. 30, 2024 USD ($) $ / shares shares	Mar. 31, 2024 USD ($)	Jun. 30, 2025 USD ($) $ / shares shares	Jun. 30, 2024 USD ($) $ / shares shares	Dec. 31, 2024 USD ($) shares	Dec. 31, 2023 shares	Jun. 30, 2025 USD ($) $ / shares shares	Jun. 05, 2025 USD ($)
Warrants and Rights Outstanding	[1]						$ 40,000				$ 40,000				$ 40,000
Class of Warrant or Right, Issued During Period (in shares) | shares												4,127,516
Stock Issued During Period, Value, Issued for Services							$ 212,000	$ 61,000	$ 116,000	$ 83,000
Share Price (in dollars per share) | $ / shares							$ 0.21				$ 0.21				$ 0.21
Financing Receivable, after Allowance for Credit Loss																$ 3,572,000
Clyra Medical [Member] | Common Stock [Member]
Investment Owned, Balance, Shares (in shares) | shares							5,305,156				5,305,156		5,305,156		5,305,156
Clyra Medical [Member] | Preferred Stock, Series A [Member]
Investment Owned, Balance, Shares (in shares) | shares							165,765				165,765		165,765		165,765
Measurement Input, Price Volatility [Member]
Warrants and Rights Outstanding, Measurement Input							0				0				0
Minimum [Member] | Measurement Input, Price Volatility [Member]
Warrants and Rights Outstanding, Measurement Input													0.64
Maximum [Member] | Measurement Input, Price Volatility [Member]
Warrants and Rights Outstanding, Measurement Input													0.95
Clyra Medical [Member]
Shares, Issued (in shares) | shares							10,878,410				10,878,410		10,544,527		10,878,410
Shares, Outstanding (in shares) | shares							10,878,410				10,878,410		10,544,527		10,878,410
Stock Issued During Period, Shares, New Issues (in shares) | shares											49,167
Proceeds from Issuance or Sale of Equity											$ 295,000
Finance Lease, Liability							$ 405				405				$ 405
Clyra Medical [Member] | Sale Leaseback of Equipment [Member]
Proceeds from Sale of Property, Plant, and Equipment		$ 350,000
Financing Receivable, after Allowance for Credit Loss		$ 82,000
Receivable with Imputed Interest, Effective Yield (Interest Rate)		15.00%
Lessee, Finance Lease, Purchase Option, Amount		$ 82,000
Lessee, Finance Lease, Term of Contract (Year)		49 years
Finance Lease, Liability							$ 524,000				$ 524,000				$ 524,000
Clyra Medical [Member] | Share-Based Payment Arrangement, Option [Member]
Share Price (in dollars per share) | $ / shares					$ 4.5				$ 4.5			$ 4.5
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Discount Rate												30.00%
Clyra Medical [Member] | Vendors [Member]
Stock Issued During Period, Shares, New Issues (in shares) | shares											9,698
Stock Issued During Period, Value, Issued for Services											$ 60,000
Clyra Medical [Member] | Employees and Consultants [Member] | Share-Based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Fair Value											$ 406,000		$ 122,000
Share Price (in dollars per share) | $ / shares							$ 4.5				$ 4.5				$ 4.5
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Discount Rate											30.00%
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount							$ 629,000				$ 629,000				$ 629,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)											2 years
Clyra Medical [Member] | Preferred Shares Issued for Debt Owed to Biolargo [Member]
Debt Conversion, Converted Instrument, Amount					$ 741,000
Debt Conversion, Converted Instrument, Shares Issued (in shares) | shares					148,156
Clyra Medical [Member] | Series A Preferred Stock [Member]
Shares, Issued (in shares) | shares							746,418				746,418		746,418		746,418
Shares, Outstanding (in shares) | shares							746,418				746,418		746,418		746,418
Shares Issued, Price Per Share (in dollars per share) | $ / shares						$ 3.1
Preferred Stock, Dividend Rate, Percentage						15.00%
Preferred Stock, Convertible, Sale of Stock Amount						$ 5,000,000
Clyra Medical [Member] | Preferred Class A [Member]
Stock Issued During Period, Shares, New Issues (in shares) | shares						746,618
Proceeds from Issuance of Preferred Stock and Preference Stock						$ 1,800,000
Clyra Medical [Member] | Revolving Credit Facility [Member] | Vernal Bay Capital Group, LLC [Member] | Inventory Line of Credit [Member]
Debt Instrument, Interest Rate, Stated Percentage				15.00%
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) | shares				32,200
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		$ 134,000		134,000
Clyra Medical [Member] | Warrants Issued Concurrently with Note Payable [Member]
Debt Instrument, Face Amount							$ 575,000				$ 575,000				$ 575,000
Debt Instrument, Interest Rate, Stated Percentage							15.00%				15.00%				15.00%
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares							$ 6				$ 6				$ 6
Clyra Medical [Member] | Warrant In Connection With Convertible Note [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares							$ 7.5				$ 7.5				$ 7.5
Warrants and Rights Outstanding							$ 231,000				$ 231,000				$ 231,000
Long-Term Debt, Gross							$ 575,000				$ 575,000				$ 575,000
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares) | shares							88,462				88,462				88,462
Clyra Medical [Member] | Warrant In Connection With Convertible Note [Member] | Measurement Input, Share Price [Member]
Warrants and Rights Outstanding, Measurement Input							6				6				6
Clyra Medical [Member] | Warrant In Connection With Convertible Note [Member] | Minimum [Member]
Debt Instrument, Convertible, Conversion Price (in dollars per share) | $ / shares							$ 6				$ 6				$ 6
Clyra Medical [Member] | Warrant In Connection With Convertible Note [Member] | Maximum [Member]
Debt Instrument, Convertible, Conversion Price (in dollars per share) | $ / shares							$ 7.5				$ 7.5				$ 7.5
Clyra Medical [Member] | Warrants Issued With Secured Promissory Notes and Convertible Promissory Notes [Member]
Class of Warrant or Right, Discount Percentage							30.00%				30.00%				30.00%
Clyra Medical [Member] | Warrants Expiring February 28, 2027 [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares					$ 7.5		$ 7.5		$ 7.5		$ 7.5	$ 7.5			$ 7.5
Warrants and Rights Outstanding							$ 38,000				$ 38,000				$ 38,000
Stock Issued During Period, Shares, New Issues (in shares) | shares												223,000
Class of Warrant or Right, Issued During Period (in shares) | shares											24,584
Number of Accredited Investors					5		5		5		5	5			5
Proceeds from Issuance or Sale of Equity												$ 1,115,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) | shares					111,500				111,500			111,500
Clyra Medical [Member] | March 31, 2025 Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares							$ 6				$ 6				$ 6
Warrants and Rights Outstanding							$ 6,000				$ 6,000				$ 6,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) | shares							7,849				7,849				7,849
Warrants and Rights Outstanding, Term (Month)							5 years				5 years				5 years
Clyra Medical [Member] | Warrants Issued in Conjunction With the Sale of Series A Preferred Stock [Member]
Warrants and Rights Outstanding						$ 524,000
Warrants and Rights Outstanding, Term (Month)						3 years
Shares Issued, Price Per Share (in dollars per share) | $ / shares						$ 3.72
Clyra Medical [Member] | Notes Payable, Other Payables [Member]
Debt Instrument, Face Amount							$ 436,000				$ 436,000				$ 436,000
Debt Instrument, Interest Rate, Stated Percentage							15.00%				15.00%				15.00%
Warrants and Rights Outstanding							$ 99,000				$ 99,000				$ 99,000
Long-Term Debt, Gross							1,300,000				1,300,000		840,000		1,300,000
Clyra Medical [Member] | Convertible Debt [Member]
Debt Instrument, Face Amount							$ 250,000				$ 250,000				$ 250,000
Debt Instrument, Interest Rate, Stated Percentage							10.00%				10.00%				10.00%
Warrants and Rights Outstanding							$ 80,000				$ 80,000				$ 80,000
Long-Term Debt, Gross							$ 250,000				$ 250,000		200,000		$ 250,000
Debt Instrument, Term (Year)											2 years
Debt Instrument, Convertible, Conversion Price (in dollars per share) | $ / shares							$ 6				$ 6				$ 6
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares) | shares							72,667				72,667				72,667
Clyra Medical Technologies [Member]
Preferred Stock Dividends and Other Adjustments											$ 762,000		$ 590,000
Clyra Medical Technologies [Member] | Warrants Issued With Secured Promissory Notes and Convertible Promissory Notes [Member] | Minimum [Member] | Measurement Input, Price Volatility [Member] | Valuation Technique, Black-Scholes-Merton Model [Member]
Warrants and Rights Outstanding, Measurement Input							35				35				35
Clyra Medical Technologies [Member] | Warrants Issued With Secured Promissory Notes and Convertible Promissory Notes [Member] | Maximum [Member] | Measurement Input, Price Volatility [Member] | Valuation Technique, Black-Scholes-Merton Model [Member]
Warrants and Rights Outstanding, Measurement Input							43				43				43
Clyra Medical Technologies [Member] | Warrant Holder Unit Offering [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares							$ 7.5				$ 7.5				$ 7.5
Warrants and Rights Outstanding							$ 172,000				$ 172,000				$ 172,000
Class of Warrant or Right, Issued During Period (in shares) | shares							237,774
Proceeds from Issuance or Sale of Equity							$ 1,309,000
Clyra Medical Technologies [Member] | Warrant Holder Unit Offering [Member] | Minimum [Member]
Class of Warrants or Rights, Purchase Price Per Share (in dollars per share) | $ / shares							$ 3.72				$ 3.72				$ 3.72
Clyra Medical Technologies [Member] | Warrant Holder Unit Offering [Member] | Maximum [Member]
Class of Warrants or Rights, Purchase Price Per Share (in dollars per share) | $ / shares							6.5				6.5				6.5
Clyra Medical Technologies [Member] | Warrant Holder Unit Offering [Member] | Median [Member]
Class of Warrants or Rights, Purchase Price Per Share (in dollars per share) | $ / shares							$ 6				$ 6				$ 6
Vernal Bay Capital Group, LLC [Member] | Conversion of Clyra Medical Stock Into Biolargo Common Stock [Member]
Stock Issued During Period, Shares, Commitment Fee (in shares) | shares														32,200
Conversion of Stock, Shares Issued (in shares) | shares			527,983

[1] Aggregate intrinsic value based on closing common stock price of $0.21 at June 30, 2025.