Note 9 - Business Segment Information - Segment Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Revenue	$ 1,500,000	$ 712,000	$ 3,786,000	$ 1,743,000
Operating loss	(943,000)	(1,455,000)	(3,973,000)	(5,013,000)
Interest expense	(14,000)	(26,000)	(42,000)	(208,000)
Research and development	(271,000)	(344,000)	(1,018,000)	(1,027,000)
Tangible assets	3,442,000		3,442,000		$ 2,522,000
Operating Lease, Right-of-Use Asset	896,000		896,000		453,000
Investment in South Korean joint venture	33,000		33,000		48,000
Total	4,371,000		4,371,000		3,023,000
Investment in South Korean Joint Venture [Member]
Investment in South Korean joint venture	33,000		33,000		48,000
Corporate, Non-Segment [Member]
Revenue	2,000	0	4,000	7,000
Operating loss	(783,000)	(868,000)	(2,925,000)	(2,726,000)
Interest expense	(6,000)	(6,000)	(18,000)	(106,000)
Research and development	(140,000)	(220,000)	(570,000)	(765,000)
Tangible assets	785,000		785,000		690,000
Operating Lease, Right-of-Use Asset	157,000		157,000		222,000
Total	975,000		975,000		960,000
Corporate, Non-Segment [Member] | Investment in South Korean Joint Venture [Member]
Investment in South Korean joint venture	33,000		33,000		48,000
Operating Segments [Member] | Odor-No-More [Member]
Revenue	1,199,000	420,000	2,499,000	1,058,000
Operating loss	400,000	(72,000)	418,000	(355,000)
Tangible assets	1,079,000		1,079,000		451,000
Operating Lease, Right-of-Use Asset	0		0		0
Total	1,079,000		1,079,000		451,000
Operating Segments [Member] | Odor-No-More [Member] | Investment in South Korean Joint Venture [Member]
Investment in South Korean joint venture	0		0		0
Operating Segments [Member] | Clyra Medical [Member]
Tangible assets	814,000		814,000		832,000
Operating Lease, Right-of-Use Asset	0		0		0
Total	814,000		814,000		832,000
Operating Segments [Member] | Clyra Medical [Member] | Investment in South Korean Joint Venture [Member]
Investment in South Korean joint venture	0		0		0
Operating Segments [Member] | BLEST [Member]
Tangible assets	590,000		590,000		445,000
Operating Lease, Right-of-Use Asset	739,000		739,000		231,000
Total	1,329,000		1,329,000		676,000
Operating Segments [Member] | BLEST [Member] | Investment in South Korean Joint Venture [Member]
Investment in South Korean joint venture	0		0		0
Operating Segments [Member] | BioLargo Water [Member]
Revenue	1,000	2,000	1,000	9,000
Operating loss	(141,000)	(156,000)	(572,000)	(461,000)
Research and development	(119,000)	(109,000)	(446,000)	(366,000)
Tangible assets	194,000		194,000		152,000
Operating Lease, Right-of-Use Asset	0		0		0
Total	194,000		194,000		152,000
Operating Segments [Member] | BioLargo Water [Member] | Investment in South Korean Joint Venture [Member]
Investment in South Korean joint venture	0		0		0
Operating Segments [Member] | BioLargo Engineering, Science & Technologies, LLC [Member]
Revenue	401,000	416,000	1,613,000	1,070,000
Operating loss	(179,000)	(140,000)	(158,000)	(513,000)
Research and development	(100,000)	(123,000)	(288,000)	(358,000)
Operating Segments [Member] | Clyra Segment [Member]
Revenue	17,000	9,000	34,000	114,000
Operating loss	(240,000)	(219,000)	(736,000)	(958,000)
Interest expense	(8,000)	(20,000)	(24,000)	(96,000)
Research and development	(31,000)	(20,000)	(73,000)	(53,000)
Consolidation, Eliminations [Member]
Revenue	(120,000)	(135,000)	(365,000)	(522,000)
Research and development	119,000	$ 135,000	359,000	$ 515,000
Tangible assets	(20,000)		(20,000)		(47,000)
Operating Lease, Right-of-Use Asset	0		0		0
Total	(20,000)		(20,000)		(47,000)
Consolidation, Eliminations [Member] | Investment in South Korean Joint Venture [Member]
Investment in South Korean joint venture	$ 0		$ 0		$ 0