Cosign: The New Website Challenging LinkedIn
Quick Reads:
- Cosign is a new website, not an app, built by a16z’s Erik Torenberg and David Booth to be a more accurate version of LinkedIn for the startup world.
- It works like a searchable directory of investors, companies, and operators, so you can quickly find who’s real, who worked with who, and who’s worth watching.
- Endorsements stick to your profile permanently, and you can privately signal interest in hiring, investing, or working with someone without any public rejection risk.
Cosign is a new website, not an app, built for people in the startup world: founders, investors, and operators. It’s not meant to replace your resume or your Twitter feed. Think of it as a place where your actual work history and real professional reputation live, verified by the people who were there with you, instead of scattered across old posts and half-updated LinkedIn profiles.
Launched by Andreessen Horowitz, one of the biggest venture capital firms in tech, built by Erik Torenberg and David Booth, who says they’ve wanted to build this for seven years but didn’t have “the firepower” to make it happen until now.
“Cosign is a community, not a business.”- Erik Torenberg, announcing Cosign
Who Built It, And Why Now
Cosign is the first product to come out of a16z’s newly formed New Media product team. Torenberg, who recruited the team, has spent years trying to build something like it. Earlier in his career at Product Hunt, he helped builders get their work discovered by the right people; in 2016, he launched the Rise Awards to recognize tech talent that wasn’t getting enough credit. David Booth, a16z’s Partner and Head of Ecosystem, brings his own history in building networks, having previously co-founded On Deck and worked early at both AngelList and Carta.
According to a16z, the reason the idea works now, after seven years of false starts, comes down to AI. The core product team is just three people, two of them former founders or CEOs, and they lean on AI to auto-populate company data, auto-research information online, filter out spam, and generate an ongoing “industry watch” feed, work that would have taken a much larger team to do manually.
How Cosign Actually Works
At its core, Cosign is a directory: a searchable list of investors, companies, and operators, showing what each person worked on and who they worked with. That alone solves a real, everyday problem in the startup world. If you’re trying to find a good fintech investor or figure out which AI companies are worth watching, you normally have to ask around your network for weeks and hope someone points you in the right direction. Cosign is meant to answer that in a search bar.
Beyond the directory, Cosign tracks something most networking platforms don’t bother capturing: real working relationships. Not just “connected,” but who actually shaped your career, who you were in the trenches with, and who would work with you again if given the chance. Those endorsements stick to a person’s profile permanently, instead of getting a few likes on social media and disappearing into the feed a week later.
A Directory Built Around Real, Verified People
Because access is invite-based rather than open to anyone with an email address, the people and companies listed on Cosign are meant to be substantiated by actual working history, not self-reported titles or inflated bios. The directory’s promise is that a name on Cosign, whether it’s a known investor, a startup operator, or someone further along at an established tech company, is backed by people who’ve genuinely worked alongside them, rather than a profile they built themselves. That’s the credibility problem Cosign is trying to solve: on other networks, anyone can claim a connection or an achievement; here, the goal is that reputation only sticks if the people who actually worked with you say it does.
There’s also a private layer for signaling interest. Members can quietly indicate “I’d hire this person,” “I’d invest in this company,” or eventually “I’d acquire this company,” and the platform only surfaces a match when the interest goes both ways. That removes a lot of the awkwardness of cold outreach, since nobody sees a rejected signal.
Access to Cosign isn’t Open by Default
New members need to be “cosigned” by someone already on the platform, though applying directly is also an option for people without an existing connection there. Torenberg has compared the concept to what you’d get “if Wikipedia, LinkedIn, and OG AngelList had a baby,” combining a reference encyclopedia, a professional network, and an early-stage community in one place.
Cosign is live now at cosign.co, with applications open to founders, investors, and operators who want in.
