Substack raises $65M Series B led by Andreessen Horowitz
Substack BlogHamish McKenzie
Context & Ripple Effects
The raise was leaked a day earlier: Axios reported Substack raising $65M at a $650M valuation with Andreessen Horowitz leading. For a16z this is a repeat bet — it also led the company's $15.3M Series A in 2019, when Substack counted 50,000 paying subscribers across its newsletters.
The arc matters because the valuation barely moves for years afterward. By mid-2025 Substack was still pitching a round above only ~$700M while generating about $45M in ARR (Newcomer), before the $100M Series C finally pushed it to a $1.1B valuation — four years for the price of this round to double.
First-order effects
Substock's treasury jumps tenfold from its Series A, giving it runway to push past email newsletters into broader products — which is where its 2025 social-network and advertising ambitions ultimately land.
Andreessen Horowitz deepens its position as Substack's anchor institutional investor, now having led both priced rounds to date.
Second-order effects
Two years later Substack turns its own writers into investors, opening the Series B as an extension via community raises of $2M and then $5M+ (Axios) — converting the people who earn on the platform into stakeholders who keep capital inside it.
A $650M price on newsletter subscription revenue pressures competing creator-monetization platforms to justify their own multiples against a business whose ARR growth proved slower than the headline valuation implied.
Third-order effects
If the pattern holds, creator-economy platforms are valued less on current revenue than on optionality toward media networks — the gap between Substack's ~$45M ARR and its eventual $1.1B mark suggests investors are underwriting distribution, not subscriptions.
Repeat lead investors like a16z effectively set the private pricing floor for their portfolio companies across successive rounds, making founder-friendly community extensions a tool to sustain momentum between institutional marks.
The trend: Creator-platform valuations are compounding ahead of revenue, with a16z anchoring every priced round and writer-community sales bridging the gaps.
Substack wrote a little bit about what it plans to spend its new $65 million investment on. The most eye-catching item on here is “investing in initiatives to support local news and reporting.” https://blog.substack.com/...
Huh! I wonder if there's any correlation between this news and how Andreessen's least favorite NYT journalist gets dogpiled by Substack writers and their followers every few weeks. Probably not. https://twitter.com/...
congrats i guess, but as a regular user of substack this fills me with dread... $65M of vc money means the company needs to succeed in a very specific way or it will be acquired and/or sunsetted at some point. i love tech, but at this point vc money into my fav products scares me…
Page me if (when?) they up their fee to 20-30% and start making it difficult to export your subs lists. Because that kind of Vc money comes W a lot of strings and growth goals https://twitter.com/...
Substack is becoming a weird hybrid of tech platform, book publisher, and VC: https://blog.substack.com/... I don't know if it will work, but it's going to be fascinating to watch!
Announcement: A16z is leading Substack's $65M Series B! This is one of my favorite startups on many levels, as a writer/author. I'm proud to be an investor 😎 The funding will be used to provide deeper value for writers on the platform. Details: https://blog.substack.com/...
A yikes from me, Bos. Just because Facebook is aware of its problems doesn't mean it's actually going to enact change when it's antithetical to its bottom line. In fact, these issues are still up for debate today on already established “flat” platforms. https://www.technologyrevi…
This is an excellent 10 minutes with Boz on the topics of security, privacy and trust with your #VR data. This is worth watching and understanding that the goals of VR are human and societal improvement and not another way to abscond with your data. https://twitter.com/...
I'm really glad to see more efforts from @FBRealityLabs & @boztank to start a public conversation about some of the ethical & privacy implications of augmented & virtual reality. Look for me to dig into some of the low-level specifics + contextual & relational dynamics here soon.…
This interview last night with @boztank (VP of Reality Labs at Facebook) & @emilychangtv is one of the best about #AugmentedReality & #VirtualReality I've seen that anyone can easily understand. Emily got Andrew to explain #AR & #VR's future in such simple terms for everyone http…
Substack announces $65 million in new funding, promises major investment in writers including, “more fellowships, grants, mentorship programs, educational resources, events.” https://blog.substack.com/... via @SubstackInc