Andreessen Horowitz — a16z — is one of the most influential venture firms in the world, founded in July 2009 by Marc Andreessen and Ben Horowitz, headquartered in Menlo Park, and managing over $90B-$100B+ in assets across a portfolio of more than 1,000 companies. But a venture portfolio has a second, quieter signature: how much of it is programmable. On APIs.io, that signature is measurable.
The footprint on the network
The network tracks 1,100 a16z portfolio companies, and 186 of them — 17% — publish APIs indexed here. That is the firm’s real API footprint: not the whole portfolio, but the slice that has shipped a public developer surface.
The distribution is telling. Only 8 portfolio companies land in the exemplar band — complete, well-documented, and agent-ready:
- Stripe (composite 80.1, 57 APIs)
- Asana (74.8, 45 APIs)
- Svix (73.5, 4 APIs)
- Databricks (73.3, 57 APIs)
- Twilio (73.2, 35 APIs)
- Zapier (73.2, 4 APIs)
- Solana (71.4, 7 APIs)
- Amplitude (70.2, 20 APIs)
Below them, 27 companies sit in the strong band — Figma, Webflow, GitHub (65 APIs), Slack (39 APIs), OpenAI (25 APIs), Box (51 APIs), Okta, Mistral AI — and 45 more in developing, before a long tail of 52 thin, 50 emerging, and 4 minimal.
One observation
The exemplars are almost entirely developer infrastructure and fintech: Stripe, Twilio, Svix, Databricks, Zapier. These are companies whose product is the API, so a mature, agent-ready surface is not a nice-to-have — it is the business. Contrast that with a16z’s most famous consumer and frontier bets. Airbnb sits in developing (53.8), Coinbase in developing (55.5), and defense and hard-tech names like Anduril (29.0), Skydio (39.7), Saronic (16.5), and Shield AI (17.0) score in the emerging or thin bands. The pattern is clear: the companies that publish strong public APIs are the ones selling to developers, while the frontier-tech portfolio is largely closed at the network layer.
Fintech is the other cluster worth watching. Beyond Stripe, the portfolio carries Plaid (39 APIs), Coinbase, Mercury, Wise, Affirm, and Cross River Bank — a dense financial-infrastructure footprint, though most of it lands in developing or thin rather than exemplar.
Takeaway
A venture portfolio’s API footprint is a proxy for how much of it builds for other builders. For a16z, 186 of 1,100 tracked companies publish APIs, but the quality concentrates hard at the top — developer tools and payments are exemplary, while consumer and frontier tech are largely un-indexed or early. See the full banded portfolio, from exemplar to minimal, at apis.io/vcs/a16z.