The Sixth Force: Complementors in Five Forces Analysis
A complementor is a company whose product makes yours more valuable — apps to a smartphone, games to a console, integrations to a SaaS tool. Some strategists add complementors to Porter's Five Forces as a "sixth force." Porter's canonical model, though, contains exactly five; the sixth force is a proposed extension, not part of the original.
Quick Answer: Complementors are the proposed "sixth force" in competitive analysis — players whose products increase demand for yours. The idea comes from Andy Grove's Only the Paranoid Survive and from Brandenburger and Nalebuff's Co-opetition, not from Porter. Add them to your analysis when you compete in platforms, ecosystems, or integration-heavy markets.
Porter's Five Forces is a map of the pressures that squeeze profit out of an industry: new entrants, suppliers, buyers, substitutes, and rivals. Every one of them is, in effect, a threat. But sit inside a real market and you notice something the map leaves out — some companies make you more money by existing, not less. A payments API makes an e-commerce platform more useful. Those are complementors, and whether they deserve a formal seat at the table is one of strategy's longest-running arguments. If you are new to the base model, start with our guide to Porter's Five Forces for startups.
Complementors vs. competitors: two mirror-image relationships
A company is your complementor when customers value your product more because the other product exists, and your competitor when they value it less. Brandenburger and Nalebuff drew it exactly that way in Co-opetition: complementors and competitors sit on opposite sides of their "Value Net," a four-player schematic of customers, suppliers, competitors, and complementors.
The distinction flips the strategic goal. With a competitor, you fight over a fixed pie — every sale they win is one you lose. With a complementor, you both benefit from growing the pie — more games sold means more consoles sold. That positive-sum dynamic is what the authors named co-opetition: players cooperate to create value, then compete to capture it.
Here is how the three player types compare on the one thing that matters — what they do to how much customers value you.
| Player type | Effect on your product's value | Underlying relationship | Everyday example |
|---|---|---|---|
| Complementor | Raises it — customers want you more when the other exists | Positive-sum: grow the pie together | Game studios to a console maker |
| Competitor / rival | Lowers it — customers want you less when the other exists | Rivalrous: split a fixed pie | A second console maker |
| Substitute | Replaces it — customers pick the other instead of you | Threat: substitution away | Cloud gaming vs. owning a console |
Takeaway: Complementors are the only player type here that can make your market bigger rather than just redividing it — which is exactly why some argue the five-force map is incomplete without them.
Why strategists propose complementors as a sixth force
Complementors get proposed as a sixth force because all five of Porter's forces describe threats — pressures that compete away your profit — while complementors can expand the profit pool itself. Left out, the model only ever sees how an industry destroys value, never the players who create it.
The extension has two well-known parents, both from 1996. In Only the Paranoid Survive, Intel's Andy Grove argued that Porter's model needed a sixth force to capture complementors — companies whose products, like the software running on Intel's chips, made his own more valuable. The same year, Adam Brandenburger and Barry Nalebuff formalized the idea in Co-opetition, giving complementors an equal seat in the Value Net.
Porter himself has never adopted the addition. His position, argued in later writing, is that complements are real and important but not a separate force determining profitability — instead they act through the existing five, changing demand, the threat of substitutes, or the barriers to entry. So the honest framing: the five forces are canonical, and complements are a genuine factor; whether that factor earns the title of a standalone "sixth force" is a modeling choice, not settled doctrine — and one of the sharper items on any list of where Five Forces falls short for startups.
Startup examples of complementors: integrations, platforms, and ecosystems
For most startups, complementors show up in three recognizable shapes — integration partners, platform developers, and the wider ecosystem around a standard. Each raises your product's value in a slightly different way, and each creates a slightly different dependency.
Integrations: partner apps that make your product stickier
An integration is a complementor you can see on your settings page. When your project tool connects to Slack, Google Calendar, and Zapier, each makes yours more useful without you building their features — and customers who depend on those connections are harder to pry loose, so the integrations quietly become switching costs. The dependency runs both ways: if a partner changes its API or pricing, your value shifts with it.
Platforms: developers who build on top of you
If other companies build products on yours, you are a platform and they are your complementors. Apple's App Store is the textbook case — every useful app makes an iPhone more valuable, and Apple never had to write it. Game consoles work the same way: PlayStation and Nintendo compete partly on who attracts the best studios.
Ecosystems: the whole market around a standard
Sometimes the complementor is an entire category rather than one firm. Electric vehicles are worth more when a dense charging network exists, and the network is worth more when more EVs are on the road — neither controls the other, yet each needs the other's growth. Grove's own example had this shape: more capable software made Intel's faster chips worth buying, so the software industry acted as a complementor to Intel.
Mapped out, the pattern is consistent across all three shapes.
| Your product | Its complementor | Why value rises together |
|---|---|---|
| SaaS project tool | Slack, Zapier, calendar apps | Each integration extends what your tool can do |
| Smartphone | Third-party app developers | More apps make the device more useful to own |
| Game console | Independent game studios | Strong exclusive titles sell the hardware |
| Electric vehicle | Public charging network | Each side's growth makes the other more practical |
Takeaway: In every row, neither company fully succeeds alone — the source of both the upside and the risk. A complementor that lifts your value today can capture it tomorrow or turn into a competitor, so mapping them belongs in your broader competitor analysis playbook alongside your rivals.
When complementor strategy matters most
Complementors matter most when your product only reaches its full value alongside someone else's — platforms, marketplaces, hardware-plus-software, and any market thick with integrations. For a standalone, self-contained product, the five forces alone usually tell the story, and bolting on a sixth force just adds noise.
The tell is dependency. If a large share of your value is created by products you do not own, you are in complementor territory and should model those players deliberately: who are they, how healthy are they, and who is splitting the value? This is also where complementors blur into other moats — a thriving complement ecosystem often produces network effects as a moat.
The flip side is platform risk. Depend on a complementor and you inherit their decisions — a pricing change, an API deprecation, or a strategic pivot can erase value you did not create and cannot protect. The discipline is to name your complementors explicitly, alongside the five forces rather than instead of them, and keep asking who captures the value you build together — the kind of structured mapping a tool like Edmired is built to keep in one place.
Key Takeaways
- A complementor makes your product more valuable. Customers want you more when the complement exists — apps to a phone, games to a console, integrations to a SaaS tool.
- The sixth force is a proposed addition, not part of Porter's model. Porter's Competitive Strategy defines exactly five forces; complementors were added by other thinkers later.
- Credit goes to Grove and to Brandenburger and Nalebuff. Andy Grove's Only the Paranoid Survive and the Value Net in Co-opetition both introduced complementors as a distinct player in 1996.
- Complementors are the mirror image of competitors. Competitors make customers value you less and split a fixed pie; complementors make them value you more and grow it together.
- Porter treats complements as a factor, not a force. In his view they shape the existing five forces rather than forming a sixth — so the "sixth force" label is a modeling choice, not consensus.
- Dependency is the price of the upside. A complementor can raise your value and then capture it, so always model who splits the jointly created value.
- The sixth force earns its place in platform and ecosystem markets. For standalone products, the original five forces usually suffice.
Frequently Asked Questions
Are complementors part of Porter's Five Forces?
No. Porter's original model in Competitive Strategy has exactly five forces — new entrants, suppliers, buyers, substitutes, and rivalry. Complementors are a proposed sixth force added later by Andy Grove and by Brandenburger and Nalebuff. Porter himself treats complements as a factor that influences the five forces, not as a separate one.
What is an example of a complementor?
App developers are complementors to a smartphone maker: every useful app makes the phone more valuable, yet the phone maker never had to build it. Other examples include game studios to a console, charging networks to electric vehicles, and Slack or Zapier integrations to a SaaS tool.
What is the difference between a complementor and a substitute?
They are opposites. A substitute replaces your product — customers buy it instead of yours, which is why substitution is one of Porter's five forces. A complementor is bought alongside yours and makes it more valuable. Cloud gaming can substitute for a console; a game studio complements it — one pushes customers away, the other pulls them in.