a16z Wants to Build a Better LinkedIn for Startups

by Dee Miller

Andreessen Horowitz has launched Cosign, a new professional network built specifically for the startup world.

The idea is simple. LinkedIn tells you where someone has worked. Cosign wants to tell you who actually rates them.

Launched on 25 September, Cosign is a curated network for founders, investors, operators and companies. Members can build profiles, endorse people they have worked closely with and create lists around standout talent, companies and sectors. Access is currently curated, with people able to join through an existing member or apply directly.

Where it gets more interesting is its “intent network.”

Users can privately signal that they would invest in someone, hire them, work with them or potentially acquire their company. When that interest is mutual, Cosign can help connect the two sides.

That makes it less like another social feed and more like a reputation and discovery layer for Silicon Valley.

Instead of endorsements disappearing into X posts, Cosign is designed to attach those signals permanently to people and companies. It can also surface answers to questions such as which founders are worth watching, who the strongest fintech angels are or which operators people would happily work with again.

The project has been introduced by Erik Torenberg, David Booth, Dani Grant and Katie Kirsch, and fits into a16z’s broader push to build its own startup ecosystem through initiatives such as a16z Build, its community for founders and operators.

Cosign’s own homepage already combines profiles, community rankings, curated lists, industry updates and startup jobs in one place.

The bigger point is that a16z is no longer simply investing in networks.

It is starting to build one of its own.

And if LinkedIn became the professional identity layer for the wider working world, Cosign is making a bet that the startup ecosystem deserves something much more specific.

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