Stack Exchange


Today we are announcing that A16z is leading a $40M investment in Stack Exchange, along with earlier investors USV, Bezos Expeditions, Spark, and Index.

1 5dOUhQl1ati7FpCfQehhrQ

Stack Exchange is a network of 133 sites (and growing) where people can ask and answer questions about topics related to engineering, science, hobbies, and more. The biggest site on the network is Stack Overflow, which alone gets over 40 million unique visitors per month. The other sites cover a very wide variety of topics, including: math, gardening, English language usage, graphic design, physics, cryptography, chess, astronomy, Buddhism, data science, martial arts, home improvement, photography, bicycles, board games, economics, to name a few. Most likely, you’ve used Stack Exchange without even knowing it —the network had over 300M unique visitors last year. Many users come in through Google, get their answer, and then leave, usually a little bit smarter.

One of the major startup opportunities of the information age is: now that more than two billion people have internet-connected devices, how do we create systems to efficiently share and store their collective knowledge? Requirements for successful collective knowledge systems include: 1) users need to be given the proper incentives to contribute, 2) the contributions of helpful users need to make the system smarter (not just bigger), and 3) users with malicious intent can’t be allowed to hurt the system.

Many entrepreneurs and inventors have tried and failed to solve this problem. As far as I know, only two organizations have succeeded at scale: Stack Exchange and Wikipedia. Stack isn’t as large as Wikipedia on the readership side — the topics are more specialized—but, on the contributor side, is closely comparable to Wikipedia. Last year, Stack had over 300 million unique visitors, and 3.8 million total registered users, who contributed over 3.1M questions, 4.5M answers, 2.7M edits, and 17M comments.

Stack’s business model is based on job placement. Employers create company pages (here is Amazon’s—over 6000 companies have created pages) and then run targeted ad campaigns for open job opportunities. Revenue has grown quickly, and the company employs over 200 people. The HQ is in NYC, with offices in Denver and London, and remote workers in Israel, Brazil, Japan, Germany, Slovenia, France, and across the US.

I believe Stack Exchange’s growth has now reached escape velocity. Not only will the existing topics continue to grow, but many new topics will emerge, until the network covers every topic that is amenable to objective Q&A. As new generations of people grow up on the internet, old habits — searching through textbooks or how-to books, or asking friends—will fade away. People will come to expect that any objective question can be instantly answered with a Google search.

I’ve been a personal investor in Stack since its initial funding, and it has always been one of my favorite investments. Stack’s cofounder & CEO, Joel Spolsky, is an amazing entrepreneur and internet visionary. I’m very happy to back him again with this new investment.

Next post: Virtual reality: a new creative medium where the default state is belief
Previous post: Skydio

Views expressed in “content” (including posts, podcasts, videos) linked on this website or posted in social media and other platforms (collectively, “content distribution outlets”) are my own and are not the views of AH Capital Management, L.L.C. (“a16z”) or its respective affiliates. AH Capital Management is an investment adviser registered with the Securities and Exchange Commission. Registration as an investment adviser does not imply any special skill or training. The posts are not directed to any investors or potential investors, and do not constitute an offer to sell -- or a solicitation of an offer to buy -- any securities, and may not be used or relied upon in evaluating the merits of any investment.

The content should not be construed as or relied upon in any manner as investment, legal, tax, or other advice. You should consult your own advisers as to legal, business, tax, and other related matters concerning any investment. Any projections, estimates, forecasts, targets, prospects and/or opinions expressed in these materials are subject to change without notice and may differ or be contrary to opinions expressed by others. Any charts provided here are for informational purposes only, and should not be relied upon when making any investment decision. Certain information contained in here has been obtained from third-party sources. While taken from sources believed to be reliable, I have not independently verified such information and makes no representations about the enduring accuracy of the information or its appropriateness for a given situation. The content speaks only as of the date indicated.

Under no circumstances should any posts or other information provided on this website -- or on associated content distribution outlets -- be construed as an offer soliciting the purchase or sale of any security or interest in any pooled investment vehicle sponsored, discussed, or mentioned by a16z personnel. Nor should it be construed as an offer to provide investment advisory services; an offer to invest in an a16z-managed pooled investment vehicle will be made separately and only by means of the confidential offering documents of the specific pooled investment vehicles -- which should be read in their entirety, and only to those who, among other requirements, meet certain qualifications under federal securities laws. Such investors, defined as accredited investors and qualified purchasers, are generally deemed capable of evaluating the merits and risks of prospective investments and financial matters. There can be no assurances that a16z’s investment objectives will be achieved or investment strategies will be successful. Any investment in a vehicle managed by a16z involves a high degree of risk including the risk that the entire amount invested is lost. Any investments or portfolio companies mentioned, referred to, or described are not representative of all investments in vehicles managed by a16z and there can be no assurance that the investments will be profitable or that other investments made in the future will have similar characteristics or results. A list of investments made by funds managed by a16z is available at Excluded from this list are investments for which the issuer has not provided permission for a16z to disclose publicly as well as unannounced investments in publicly traded digital assets. Past results of Andreessen Horowitz’s investments, pooled investment vehicles, or investment strategies are not necessarily indicative of future results. Please see for additional important information.