v3.26.1
Note 11 - Business Segment Information - Segment Information (Details) - USD ($)
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Dec. 31, 2025
Revenue from Contract with Customer, Including Assessed Tax $ 1,115,000 $ 3,269,000  
Stock option expense 699,000 615,000  
Depreciation (34,000) (42,000)  
Research and development expense (907,000) (791,000)  
Operating income (loss) (3,204,000) (1,862,000)  
Operating income (loss) (3,204,000) (1,862,000)  
Interest income (expense) (116,000) (65,000)  
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest (3,405,000) (1,921,000)  
Tangible assets 7,276,000   $ 6,945,000
Operating lease right-of use 979,000   1,028,000
Finance lease right-of-use 310,000   338,000
Total 8,565,000   8,311,000
Segment Reporting, Reconciling Item, Corporate Nonsegment [Member]      
Stock option expense 286,000 409,000  
Depreciation (9,000) (11,000)  
Research and development expense (261,000) (248,000)  
Operating income (loss) (459,000) (817,000)  
Operating income (loss) (459,000) (817,000)  
Interest income (expense) 63,000 3,000  
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest (481,000) (815,000)  
Tangible assets 674,000   694,000
Operating lease right-of use 206,000   238,000
Finance lease right-of-use 0   0
Total 880,000   932,000
Operating Segments [Member] | Odor-No-More [Member]      
Revenue from Contract with Customer, Including Assessed Tax 423,000 2,803,000  
Depreciation (10,000) (10,000)  
Operating income (loss) (95,000) 956,000  
Operating income (loss) (95,000) 956,000  
Interest income (expense) 0 15,000  
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest (95,000) 971,000  
Tangible assets 2,016,000   2,331,000
Operating lease right-of use 0   0
Finance lease right-of-use 0   0
Total 2,016,000   2,331,000
Operating Segments [Member] | Clyra Segment [Member]      
Revenue from Contract with Customer, Including Assessed Tax 154,000 0  
Stock option expense 413,000 206,000  
Depreciation (2,000) (4,000)  
Research and development expense (521,000) (335,000)  
Operating income (loss) (1,712,000) (1,315,000)  
Operating income (loss) (1,712,000) (1,315,000)  
Interest income (expense) (179,000) (83,000)  
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest (1,891,000) (1,398,000)  
Tangible assets 3,520,000   2,650,000
Operating lease right-of use 169,000   175,000
Finance lease right-of-use 310,000   338,000
Total 3,999,000   3,163,000
Operating Segments [Member] | BioLargo Engineering, Science & Technologies, LLC [Member]      
Revenue from Contract with Customer, Including Assessed Tax 797,000 690,000  
Depreciation (11,000) (17,000)  
Research and development expense (208,000) (244,000)  
Operating income (loss) (380,000) (378,000)  
Operating income (loss) (380,000) (378,000)  
Tangible assets 1,022,000   1,169,000
Operating lease right-of use 604,000   615,000
Finance lease right-of-use 0   0
Total 1,626,000   1,784,000
Operating Segments [Member] | BioLargo Energy Technologies, Inc (BETI) [Member]      
Depreciation (2,000) 0  
Research and development expense (142,000) (60,000)  
Operating income (loss) (355,000) (94,000)  
Operating income (loss) (355,000) (94,000)  
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest (355,000) (94,000)  
Tangible assets 235,000   4,000
Operating lease right-of use 0   0
Finance lease right-of-use 0   0
Total 235,000   4,000
Operating Segments [Member] | BioLargo Canada [Member]      
Revenue from Contract with Customer, Including Assessed Tax 58,000 8,000  
Research and development expense (92,000) (136,000)  
Operating income (loss) (113,000) (156,000)  
Operating income (loss) (113,000) (156,000)  
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest (113,000) (150,000)  
Tangible assets 12,000   321,000
Operating lease right-of use 0   0
Finance lease right-of-use 0   0
Total 12,000   321,000
Operating Segments [Member] | BEST [Member]      
Operating income (loss) (90,000) (58,000)  
Operating income (loss) (90,000) (58,000)  
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest (90,000) (58,000)  
Operating Segments [Member] | BLEST [Member]      
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest (380,000) (377,000)  
Consolidation, Eliminations [Member]      
Revenue from Contract with Customer, Including Assessed Tax (317,000) (232,000)  
Research and development expense 317,000 $ 232,000  
Tangible assets (203,000)   (224,000)
Operating lease right-of use 0   0
Finance lease right-of-use 0   0
Total $ (203,000)   $ (224,000)