| Segment Reporting [Table Text Block] |
| | | Three Months Ended June 30, | | | Six Months Ended June 30, | |
| | | 2026 | | | 2025 | | | 2026 | | | 2025 | |
| Revenue | | | | | | | | | | | | | | | | |
| ONM Environmental | | $ | 471 | | | $ | 2,006 | | | $ | 895 | | | $ | 4,809 | |
| BioLargo corporate | | | 9 | | | | — | | | | 9 | | | | — | |
| BLEST | | | 1,090 | | | | 940 | | | | 1,888 | | | | 1,630 | |
| Clyra Medical | | | — | | | | — | | | | 154 | | | | — | |
| BioLargo Canada | | | 70 | | | | — | | | | 126 | | | | 8 | |
| Intersegment revenue | | | (392 | ) | | | (169 | ) | | | (709 | ) | | | (401 | ) |
| Total | | $ | 1,248 | | | $ | 2,777 | | | $ | 2,363 | | | $ | 6,046 | |
| | | | | | | | | | | | | | | | | |
| Stock option expense | | | | | | | | | | | | | | | | |
| BioLargo corporate | | $ | 472 | | | $ | 292 | | | $ | 758 | | | $ | 701 | |
| Clyra Medical | | | 250 | | | | 200 | | | | 663 | | | | 406 | |
| Total | | $ | 722 | | | $ | 492 | | | $ | 1,421 | | | $ | 1,107 | |
| | | | | | | | | | | | | | | | | |
| Depreciation expense | | | | | | | | | | | | | | | | |
| BioLargo corporate | | $ | (10 | ) | | $ | (10 | ) | | $ | (19 | ) | | $ | (19 | ) |
| ONM Environmental | | | (9 | ) | | | (10 | ) | | | (23 | ) | | | (23 | ) |
| BLEST | | | (8 | ) | | | (11 | ) | | | (17 | ) | | | (28 | ) |
| Clyra Medical | | | (2 | ) | | | (3 | ) | | | (4 | ) | | | (4 | ) |
| BETI | | | (2 | ) | | | (2 | ) | | | (4 | ) | | | (4 | ) |
| Total | | $ | (31 | ) | | $ | (36 | ) | | $ | (67 | ) | | $ | (78 | ) |
| | | | | | | | | | | | | | | | | |
| Research and development expense | | | | | | | | | | | | | | | | |
| BioLargo corporate | | $ | (323 | ) | | $ | (219 | ) | | $ | (584 | ) | | $ | (466 | ) |
| BLEST | | | (255 | ) | | | (82 | ) | | | (463 | ) | | | (326 | ) |
| BETI | | | (156 | ) | | | (54 | ) | | | (298 | ) | | | (113 | ) |
| BioLargo Canada | | | (87 | ) | | | (120 | ) | | | (179 | ) | | | (256 | ) |
| Clyra Medical | | | (610 | ) | | | (229 | ) | | | (1,131 | ) | | | (564 | ) |
| BCPG | | | (40 | ) | | | — | | | | (40 | ) | | | — | |
| Intersegment R&D | | | 383 | | | | 169 | | | | 700 | | | | 401 | |
| Total | | $ | (1,088 | ) | | $ | (535 | ) | | $ | (1,995 | ) | | $ | (1,324 | ) |
| | | | | | | | | | | | | | | | | |
| Operating income (loss) | | | | | | | | | | | | | | | | |
| BioLargo corporate | | $ | (889 | ) | | $ | (1,045 | ) | | $ | (1,338 | ) | | $ | (1,858 | ) |
| ONM Environmental | | | (110 | ) | | | 823 | | | | (204 | ) | | | 1,780 | |
| BLEST | | | (45 | ) | | | 16 | | | | (426 | ) | | | (364 | ) |
| BETI | | | (339 | ) | | | (122 | ) | | | (694 | ) | | | (217 | ) |
| BEST | | | (75 | ) | | | (67 | ) | | | (165 | ) | | | (125 | ) |
| BioLargo Canada | | | (105 | ) | | | (144 | ) | | | (218 | ) | | | (300 | ) |
| BCPG | | | (60 | ) | | | — | | | | (60 | ) | | | — | |
| Clyra Medical | | | (2,105 | ) | | | (1,263 | ) | | | (3,826 | ) | | | (2,580 | ) |
| Total | | $ | (3,728 | ) | | | (1,802 | ) | | $ | (6,931 | ) | | $ | (3,664 | ) |
| | | | | | | | | | | | | | | | | |
| Interest income (expense) | | | | | | | | | | | | | | | | |
| BioLargo corporate | | $ | 1 | | | $ | 3 | | | $ | 64 | | | $ | 6 | |
| ONM Environmental | | | (3 | ) | | | 33 | | | | (3 | ) | | | 47 | |
| Clyra Medical | | | (270 | ) | | | (116 | ) | | | (450 | ) | | | (198 | ) |
| Total | | $ | (272 | ) | | $ | (80 | ) | | $ | (389 | ) | | $ | (145 | ) |
| | | | | | | | | | | | | | | | | |
| Net income (loss) | | | | | | | | | | | | | | | | |
| BioLargo corporate | | $ | (888 | ) | | $ | (1,042 | ) | | $ | (1,359 | ) | | $ | (1,853 | ) |
| ONM Environmental | | | (113 | ) | | | 856 | | | | (207 | ) | | | 1,827 | |
| BLEST | | | (45 | ) | | | 16 | | | | (426 | ) | | | (363 | ) |
| BETI | | | (339 | ) | | | (122 | ) | | | (694 | ) | | | (217 | ) |
| BEST | | | (75 | ) | | | (67 | ) | | | (165 | ) | | | (125 | ) |
| BioLargo Canada | | | (105 | ) | | | (144 | ) | | | (219 | ) | | | (294 | ) |
| BCPG | | | (60 | ) | | | — | | | | (60 | ) | | | — | |
| Clyra Medical | | | (2,375 | ) | | | (1,379 | ) | | | (4,275 | ) | | | (2,778 | ) |
| Total | | $ | (4,000 | ) | | $ | (1,882 | ) | | $ | (7,405 | ) | | $ | (3,803 | ) |
| As of June 30, 2026 | | BioLargo | | | ONM | | | CLYRA | | | BLEST | | | BETI | | | BioLargo Canada | | | Elimination | | | Total | |
| Tangible assets | | $ | 515 | | | $ | 1,629 | | | $ | 2,113 | | | $ | 1,248 | | | $ | 46 | | | $ | 112 | | | $ | (203 | ) | | $ | 5,460 | |
| Operating lease right-of use | | | 173 | | | | — | | | | 162 | | | | 592 | | | | — | | | | — | | | | — | | | | 927 | |
| Finance lease right-of-use | | | — | | | | — | | | | 282 | | | | — | | | | — | | | | — | | | | — | | | | 282 | |
| Total | | $ | 688 | | | $ | 1,629 | | | $ | 2,557 | | | $ | 1,840 | | | $ | 46 | | | $ | 112 | | | $ | (203 | ) | | $ | 6,669 | |
| 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 | |
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