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Fortresses
Hard to copy, hard to dislodge, and they grow without growing costs. All three at once is rare.
21 teardownsEvery teardownFortressesEasy to copy. Won anyway.Built on rented landNumbers straight from a filingDoesn't scale. On purpose.Still here after 15 yearsOne-time money
OnlyFans
Marketplace
Took 20% of content Big Tech would not process.
$1.41B
Estimate · FY24 net rev · $7.2B GMV
One niche, one owner, constant payment risk.
★ The edge: Adult creators are unbankable elsewhere. OnlyFans built the payment rails nobody else would run, and kept the fans.
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Vinted
Marketplace
Europe's clothes resale. Buyers pay, sellers don't.
€1.1B
Stated · $1.2B · 2025 revenue, +38% YoY
Most revenue is one fee buyers love to hate.
★ The edge: Taxes buyers, not sellers. Free listing grows supply, supply grows demand — liquidity fee-charging rivals can't match.
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China Literature
Community
Readers pay by the chapter. Tencent films the hits.
$1.13B
Stated · FY24 group revenue (0772)
Free, ad-funded rivals erode the paywall.
★ The edge: It pioneered pay-per-chapter reading in 2003, then kept the rights and became China's biggest web-fiction IP owner.
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Shutterstock
Marketplace
He shot 30,000 photos to seed an empty marketplace.
$935M
Filed · revenue (FY2024)
AI image generators undercut paid stock.
★ The edge: Buyers pay flat monthly subscriptions; contributors get a royalty. Shutterstock keeps the spread on stock it never shot.
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Doximity
Community
Over 80% of US doctors are members. Pharma pays.
$570.4M
Filed · FY2025 revenue, up 20%
Leans on pharma marketing budgets
★ The edge: Founder Jeff Tangney built Epocrates first, so he already had physician trust and knew pharma pays to reach doctors
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Sansan
Data
Japan runs on business cards. Sansan digitized them.
$280M
Stated · ARR, May 2025 (¥41.5B)
The card ritual fades as work goes remote.
★ The edge: Rivals trust OCR; Sansan runs every card through human operators too — 99.9% accuracy is the data moat.
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Envato
Marketplace
The bootstrapped stock-asset market that paid out $1.3B
$245M
Stated · 2024 sale price, announced
Its subscription now cannibalizes its authors
★ The edge: Launched the marketplace, then built Tuts+ — the web's biggest design-tutorial network — to feed it buyers.
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Just Dial
Marketplace
India found local shops by phone before it had Google.
Rs 1,141.9 cr
Estimate · about $130M · FY25 revenue from ops
Google Maps is eating local discovery.
★ The edge: A decade of door-to-door sales onboarded 50M+ Indian businesses before broadband arrived — a base no crawler can copy.
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Chrono24
Marketplace
Global marketplace for pre-owned luxury watches.
€103.2M
Stated · FY2021 group accounts
Dealers could bypass; GMV swings with prices.
★ The edge: Free built-in escrow lets strangers wire $50K for a used watch across 150 countries without fear of fakes.
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Infomedia
Data
Carmakers endorse it, their dealers pay for it.
A$146.5M
Filed · FY25 revenue · pre-buyout
Tied entirely to the automotive industry.
★ The edge: Microcat is the maker-endorsed parts catalog dealers update monthly and rely on across 186 countries.
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AppSumo
Marketplace
Sells software lifetime deals to a 1.5M-buyer list.
$80M
Stated · 2023 revenue
One-time cash, no recurring revenue.
★ The edge: The product is distribution, not deals: a 1.5M-buyer list makers hand 70-80% of a Select deal to reach.
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Freelancer.com
Marketplace
He didn't build the marketplace. He bought his rivals.
A$55.3M
Filed · FY25 revenue, audited
Freelance revenue grew 0.7% in FY25.
★ The edge: Takes a cut from both sides, 10% from the worker and 3% from the client, then sells upgrades on top.
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BuiltWith
Data
Fingerprints a site's tech stack — then sells the reverse.
$14M/yr
Estimate · annual revenue (est.)
Lookup is free · lead-gen cut first
★ The edge: the lookup is free — the real moat is 18 yrs of crawl history nobody can back-fill.
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Nutrient (formerly PSPDFKit)
Dev
A lawyer fixed the pricing: $20K to $1M ARR in 8 months.
$12M ARR
Stated · 2021 · bootstrapped before PE
Investor-owned now; co-founders cashed out.
★ The edge: The SDK is embedded deep in a customer's app, so ripping it out means re-engineering. Switching cost is high.
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OnlineJobs.ph
Marketplace
Flat $69/mo to hire from 2M Filipino workers.
$10M+/yr
Stated · founder-stated, 2022
Employers cancel right after they hire.
★ The edge: 15 years of free how-to-hire content sends every 'hire a Filipino VA' search to the niche's deepest worker pool.
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BiggerPockets
Community
Real estate's town square — a free forum, 3M+ members.
$7M
Estimate · 2016 rev · last public
⚠ Need cyclical
under 1% pay
under 1% pay
★ The edge: Dorkin kept the forum free for years before charging — trust and UGC compounded into a moat rivals can't buy.
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Nomad List
Community
Find the best city to live & work as a nomad — by data.
$11K/mo
Stated · founder-stated MRR
⚠ Need·Time soft
niche + travel churn
niche + travel churn
★ The edge: the moat isn't the data — it's 11 yrs of user-filled data + community + his public brand (@levelsio), all solo.
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Deque Systems
SaaS
The accessibility test engine Google & MS use.
3 billion+ axe downloads
Stated · revenue never disclosed
Services-heavy; the engine is free.
★ The edge: Deque owns axe-core, the free engine inside Google Lighthouse and Microsoft's tester. Rivals ship its code.
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Foundry VTT
Marketplace
The virtual tabletop you buy once, not rent.
100K
Stated · Discord community members
Owners buy once - little recurring revenue.
★ The edge: Buy-once $50 license in a subscription world; users self-host, so Foundry's server costs stay near zero.
Open →
Shodan
Data
Google indexes web pages. Shodan indexes devices.
3M+
Stated · registered users
Key-person lean; Censys cloned it with VC.
★ The edge: A 15-year, continuously-crawled index of every service on the public internet — a dataset newcomers can't back-fill.
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World Anvil
SaaS
Build your fictional world — a wiki for writers & GMs.
3M+
Stated · users
⚠ Need niche
small TAM · free-heavy
small TAM · free-heavy
★ The edge: anyone can clone a wiki — the lock-in is years of your interlinked lore living inside it, plus a 3M community.
Open →