| Schedule of Segment Reporting Information, by Segment [Table Text Block] |
| | | 2025 | | | 2024 |
| Revenues | | | | | | | |
| ONM Environmental | | $ | 5,905 | | | $ | 15,597 |
| BLEST | | | 2,545 | | | | 3,197 |
| Clyra Medical | | | — | | | | — |
| BioLargo Canada | | | 86 | | | | 72 |
| Intersegment revenue | | | (771 | ) | | | (1,087 |
| Total | | $ | 7,765 | | | $ | 17,779 |
| | | | | | | | |
| Research and development | | | | | | | |
| BioLargo corporate | | $ | (865 | ) | | $ | (1,173 |
| BLEST | | | (617 | ) | | | (1,158 |
| Clyra Medical | | | (1,168 | ) | | | (827 |
| BETI | | | (274 | ) | | | (379 |
| BioLargo Canada | | | (440 | ) | | | (432 |
| Intersegment research and development | | | 771 | | | | 1,087 |
| Total | | $ | (2,593 | ) | | $ | (2,882 |
| | | | | | | | |
| Operating income (loss) | | | | | | | |
| BioLargo corporate | | $ | (3,933 | ) | | $ | (4,027 |
| ONM Environmental | | | (2,317 | ) | | | 5,920 |
| BLEST | | | (1,091 | ) | | | (1,453 |
| Clyra Medical | | | (6,065 | ) | | | (3,324 |
| BETI | | | (639 | ) | | | (642 |
| BEST | | | (276 | ) | | | (273 |
| BioLargo Canada | | | (534 | ) | | | (532 |
| Total | | $ | (14,855 | ) | | $ | (4,331 |
| | | | | | | | |
| Depreciation expense | | | | | | | |
| BioLargo corporate | | $ | (38 | ) | | $ | (42 |
| ONM Environmental | | | (41 | ) | | | (33 |
| BLEST | | | (48 | ) | | | (71 |
| Clyra Medical | | | (9 | ) | | | (9 |
| BETI | | | (9 | ) | | | — |
| Total | | $ | (145 | ) | | $ | (155 |
| | | | | | | | |
| Stock option expense | | | | | | | |
| BioLargo corporate | | $ | (1,762 | ) | | $ | (1,535 |
| Clyra Medical | | | (1,203 | ) | | | (528 |
| Total | | $ | (2,965 | ) | | $ | (2,063 |
| | | | | | | | |
| Interest income (expense) | | | | | | | |
| BioLargo corporate | | $ | 10 | | | $ | (6 |
| ONM Environmental | | | 90 | | | | 31 |
| Clyra Medical | | | (499 | ) | | | (60 |
| BLEST | | | 59 | | | | — |
| BioLargo Canada | | | — | | | | 2 |
| Total | | $ | (340 | ) | | $ | (33 |
| | | | | | | | |
| Net income (loss) | | | | | | | |
| BioLargo corporate | | $ | (3,923 | ) | | $ | (4,033 |
| ONM Environmental | | | (2,227 | ) | | | 5,951 |
| BLEST | | | (1,032 | ) | | | (1,356 |
| Clyra Medical | | | (6,564 | ) | | | (3,490 |
| BETI | | | (639 | ) | | | (642 |
| BEST | | | (276 | ) | | | (273 |
| BioLargo Canada | | | (528 | ) | | | (504 |
| Consolidated net loss | | $ | (15,189 | ) | | $ | (4,347 |
| As of December 31, 2025 | | BioLargo | | | ONM | | | Clyra | | | BLEST | | | BETI | | | BioLargo Canada | | | Elimination | | | Total | |
| Tangible assets | | $ | 694 | | | $ | 2,331 | | | $ | 2,650 | | | $ | 1,169 | | | $ | 4 | | | $ | 321 | | | $ | (224 | ) | | $ | 6,945 | |
| Operating lease right-of-use | | | 238 | | | | — | | | | 175 | | | | 615 | | | | — | | | | — | | | | — | | | | 1,028 | |
| Finance lease right-of-use | | | — | | | | — | | | | 338 | | | | — | | | | — | | | | — | | | | — | | | | 338 | |
| Total | | $ | 932 | | | $ | 2,331 | | | $ | 3,163 | | | $ | 1,784 | | | $ | 4 | | | $ | 321 | | | $ | (224 | ) | | $ | 8,311 | |
| As of December 31, 2024 | | BioLargo | | | ONM | | | Clyra | | | BLEST | | | BETI | | | BioLargo Canada | | | Elimination | | | Total | |
| Tangible assets | | $ | 775 | | | $ | 5,879 | | | $ | 1,696 | | | $ | 790 | | | | 46 | | | $ | 104 | | | $ | (234 | ) | | $ | 9,056 | |
| Operating lease right-of-use | | | 333 | | | | — | | | | — | | | | 659 | | | | — | | | | — | | | | — | | | | 992 | |
| Finance lease right-of-use | | | — | | | | — | | | | 451 | | | | — | | | | — | | | | — | | | | — | | | | 451 | |
| Investment in South Korean joint venture | | | 14 | | | | — | | | | — | | | | — | | | | — | | | | — | | | | — | | | | 14 | |
| Total | | $ | 1,122 | | | $ | 5,879 | | | $ | 2,147 | | | $ | 1,449 | | | $ | 46 | | | $ | 104 | | | $ | (234 | ) | | $ | 10,513 | |
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