The following categories exist on the wiki, and may or may not be unused. Also see wanted categories.
- Aerosol pandemic (34 members)
- Africa (103 members)
- Africa files (29 members)
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- African American Environmentalist Association (16 members)
- Agricultural subsidies (1 member)
- Agriculture (619 members)
- Agriculture manual (21 members)
- Agrivoltaic (1 member)
- Agrivoltaics (38 members)
- Agroforestry (9 members)
- Agua y Suelo para la Agricultura (ASA) (63 members)
- Aid (11 members)
- Aid and development workers (20 members)
- Air Quality (1 member)
- Air conditioning (16 members)
- Air pollution (35 members)
- Air purification (1 member)
- Air quality (20 members)
- Air travel (4 members)
- Akvo ATOC (10 members)
- Akvopedia (1 member)
- Alcohol fuels (20 members)
- Algae (5 members)
- Alternative building (122 members)
- Alternative building design (4 members)
- Alternative energy (1 member)
- Alternative propulsion (3 members)
- Amaranth (12 members)
- Ambiental (8 members)
- America files (33 members)
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- AmoSmile (61 members)
- Amsterdam (1 member)
- Anaerobic digestion (33 members)
- Analysis (8 members)
- Anatomy (7 members)
- Andhra Pradesh (2 members)
- Android App Browser Testing (1 member)
- Animal husbandry (13 members)
- Animal power (7 members)
- Animals (31 members)
- Apiculture (4 members)
- Applied Thermodynamics (1 member)
- Appropedia (36 members)
- Appropedia's Public Domain Search (15 members)
- Appropedia, Appropedia Foundation (1 member)
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- Appropriate Technology Sourcebook (342 members)
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- Aquaculture (25 members)
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- Are You Ready? An In-depth Guide to Citizen Preparedness (30 members)
- Argentina (38 members)
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- Asia (44 members)
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- Assistive Devices (3 members)
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- Attribution (1 member)
- Australia (80 members)
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- Australia sustainable community action topics (1 member)
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- Automatic translations (3,303 members)
- Aviation (1 member)
- BRIDGE (21 members)
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- Best practice (9 members)
- Beyond Dams (7 members)
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- Bibliographies (0 members)
- Bicycle (4 members)
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- Biochar (20 members)
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- Biodiversity (26 members)
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- Biofilters (1 member)
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- Biology (6 members)
- Biomass (2 members)
- Biomass gasification (3 members)
- Biomimicry (3 members)
- Biophilia (1 member)
- Biotech (13 members)
- Biotico (5 members)
- Birds (16 members)
- Bittersweet (33 members)
- Blenders (17 members)
- Blind Guide (3 members)
- Bolivia (16 members)
- Bolivia files (1 member)
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- BoneDiagrams (39 members)
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- Bootcamp Caminos de Siembra (2023) (26 members)
- Bootcamp de Mapeo de Soluciones 2023 (1 member)
- Bowfishing (1 member)
- Brazil (22 members)
- Brazil files (8 members)
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- Brighton (3 members)
- Bristol (12 members)
- Bristol files (3 members)
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- British Columbia (7 members)
- British Columbia files (2 members)
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- Building elements (33 members)
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- Building with Pumice (13 members)
- Buildings (12 members)
- Built environment (127 members)
- Burning Man (8 members)
- Business (52 members)
- Butchering (8 members)
- CAD (2 members)
- CAN handbook (66 members)
- CASWiki topic news by place (1 member)
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- CASwiki UK topic news (95 members)
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- CASwiki articles with apps (27 members)
- CASwiki events files (1 member)
- CASwiki group (5 members)
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- CASwiki news archive (3 members)
- CASwiki news articles (4 members)
- CASwiki place news (81 members)
- CASwiki resources (27 members)
- CASwiki resources by place (8 members)
- CASwiki stubs (62 members)
- CASwiki topic news (131 members)
- CASwiki topics with newsfeeds (1 member)
- CBaechler (1 member)
- CC-BY-2.0 files (3 members)
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- CC-BY-NC-SA-4.0 files (4 members)
- CC-BY-SA-2.0 files (10 members)
- CC-BY-SA-2.0 images (0 members)
- CC-BY-SA-2.5 files (1 member)
- CC-BY-SA-3.0 files (7,044 members)
- CC-BY-SA-3.0 images (0 members)
- CC-BY-SA-4.0 files (9,921 members)
- CC-BY-SA-4.0 images (0 members)
- CC-ZERO files (3 members)
- CC0-1.0 files (32 members)
- CCAT (211 members)
- CCAT Building (19 members)
- CCAT active project (66 members)
- CCAT green shed (5 members)
- CCAT greywater (6 members)