26 categories, each with the trades and specialities under it. You pick one when you add a site, and the crawl checks it.
Your category does not pick your links
This trips people up, so here it is plainly. We do not match a roofer to a roofer. We read the article somebody is writing, find the paragraph in it that would genuinely be better with a source, and look for a page that is a real source for that paragraph. If the subject is local, we also check that both sides actually work in the same area.
So a roofing article can earn a link from a metal fabrication journal, and two roofers with nothing to say to each other will never be matched. The categories do a smaller job: when our reading of a page is uncertain, two related categories are evidence the pairing makes sense. They break a tie. They do not make the decision.
A site covering travel, finance, CBD and software is not a publication with a subject. It is a place to put links, and search engines read it that way too. Past 4 unrelated categories, a site goes to a person for review, and most do not get in.
Real publishers are the exception, and it is a person who grants it. A trade journal, a local paper, or a magazine covers a lot of ground because that is the job, so a reviewer can confirm a site as a publication and give it a wider spread. We never assume it: covering a lot of ground is the thing the rule is looking for, not proof against it.
Being in one category and writing about a neighbouring subject is not sprawl. Nobody is limited to writing about their own category, and nobody is limited to linking inside it.
HVAC · Plumbing · Residential Electrical · Residential Roofing · Landscaping & Lawn Care · Pool Builders & Service · Pest Control · Residential Cleaning · Commercial Cleaning · Painting · Flooring · Garage Doors · Fencing · Window & Door Installation · Handyman · Moving & Storage · Locksmith · Junk Removal · Tree Service · Pressure Washing · Septic & Well · Solar Installation · Home Security & Automation · Appliance Repair · Chimney Sweep · Gutter Services · Home & Local Services (other)
General Contractors · Commercial Construction · Remodeling & Renovation · Commercial Electrical · Concrete & Masonry · Excavation & Site Work · Framing · Commercial Roofing · Metal Fabrication & Welding · Architecture & Engineering · Land Surveying · Demolition · Insulation · Drywall · Steel Erection · Construction & Trades (other)
Primary Care & Family Medicine · General Dentistry · Cosmetic Dentistry · Orthodontics · Oral Surgery · Pediatric Dentistry · Dermatology · Chiropractic · Physical & Occupational Therapy · Mental Health, Counseling & Psychiatry · Optometry & Ophthalmology · Med Spas & Aesthetics · Plastic Surgery · Urgent Care · Home Health Care · Assisted Living & Senior Care · Addiction Treatment & Rehab · Podiatry · Audiology & Hearing · Medical Devices & Equipment · Veterinary · Medical & Healthcare (other)
Personal Injury · Estate Planning & Probate · Family Law & Divorce · Criminal Defense · Business & Corporate Law · Real Estate Law · Immigration Law · Bankruptcy · Employment Law · Tax Law · Intellectual Property · Legal Services (other)
Banking · Accounting & Bookkeeping · Tax Preparation · Financial Planning & Wealth Management · Life Insurance · Health Insurance · Auto Insurance · Home Insurance · Commercial Insurance · Mortgage & Lending · Investment & Brokerage · Payroll Services · Debt Relief & Credit Repair · Payment Processing & Fintech · Finance (other)
Aircraft Charter & Air Travel · Aircraft Maintenance & Overhaul · Flight Training · Aircraft Sales & Brokerage · Avionics & Aviation Parts · Marine Dealers & Sales · Marine Repair & Service · Marina & Boat Storage · Yacht Charter · Marine Electronics · Aviation & Marine (other)
Residential Agents & Brokerages · Commercial Real Estate · Property Management · Real Estate Investment · Title & Escrow · Home Inspection · Appraisal · Real Estate (other)
Auto Repair & Mechanics · Auto Body & Collision · Auto Sales · Auto Detailing · Towing · Tire Shops · RV & Powersports · Automotive (other)
Restaurants · Catering · Food Trucks · Bakeries · Bars & Breweries · Coffee Shops · Specialty Grocery · Restaurant & Food Service (other)
Marketing & Advertising Agencies · IT Services & Managed Providers · Web Design & Development · Staffing & Recruiting · Business Consulting · Printing · Commercial Security Services · Logistics, Freight & Trucking · Manufacturing · Wholesale & Distribution · Professional & B2B Services (other)
Women's Apparel · Men's Apparel · Children's Apparel · Footwear · Activewear & Athleisure · Swimwear · Accessories & Jewelry · Handbags & Luggage · Eyewear · Watches · Apparel & Fashion (other)
Furniture · Home Decor · Bedding & Linens · Kitchenware & Cookware · Rugs · Lighting · Outdoor & Patio Furniture · Storage & Organization · Home Goods & Furniture (other)
Consumer Electronics · Audio Equipment · Smart Home Devices · Gaming Hardware · Computer Components & Accessories · Cameras & Photography Equipment · Wearables · Electronics (other)
Toys & Games · Sporting Goods · Books · Musical Instruments · Arts & Crafts Supplies · Baby Products · Beauty Products · Pet Products · Office Supplies · Party Supplies · Retail & Specialty Goods (other)
K-12 Private Schools · Tutoring · Higher Education · Trade & Vocational Schools · Online Courses & EdTech · Education (other)
Salons & Barbershops · Day Spas · Nail Salons · Tattoo & Piercing · Beauty & Personal Care (other)
Gyms & Personal Training · Yoga & Pilates Studios · Nutrition & Wellness Coaching · Massage Therapy · Fitness & Wellness (other)
Pet Grooming · Pet Boarding & Daycare · Pet Training · Pets & Animals (other)
Charitable Foundations · Advocacy Organizations · Trade Associations & Chambers of Commerce · Community Organizations · Educational Nonprofits · Health Related Nonprofits · Nonprofit & Charity (other)
Churches & Congregations · Faith Based Ministries · Religious Publishing & Media · Faith Based Nonprofits & Missions · Religious Education · Religious & Faith (other)
Municipal & Local Government · State Government · Federal Agencies · Public Utilities · Public Safety · Courts & Judicial · Government & Public Sector (other)
Wedding Venues & Planning · Event Planning · Photography & Videography · Music & DJ Services · Art Galleries · Events, Arts & Entertainment (other)
Hotels & Lodging · Travel Agencies · Vacation Rentals · Tourism & Attractions · Travel & Hospitality (other)
SaaS · Cybersecurity · App Development · Data & AI · Technology & Software (other)
Industry & Trade Publications · Local & Regional News · Business & Financial Press · Consumer Magazines · Enthusiast & Special Interest · Broadcast & Radio · Digital Media & Newsletters · News, Media & Publications (other)
These exchange only with each other. A gambling site can earn a link from a crypto site, and neither can earn one from a roofer or give one to a dentist. It works both ways and there is no setting that opens it, because a link from one of these categories is something a site should choose on purpose and never receive by accident.
Gambling & Casino · CBD · Cannabis · Crypto · Adult · Pharmacy & Online Pharmacy · Peptides & Research Chemicals · Loans & Payday Lending · Firearms · Tobacco & Vape · Regulated & Restricted (other)
In short
Your category tells us what your site is about and which founding niche you are in. What earns you a link is having a page that is a genuinely good source for the sentence somebody is writing.
How matching works goes through it step by step.