Companies Using Substack

I'm Elif Arslan, CMO at TechnologyChecker.io, and I read Substack against our September 2026 crawl. The figure is 9,600 domains. It isn't a count of companies, and it isn't a count of Substack's writers either. We detect Substack from a response header its servers send on every page they serve (our guide to technology detection methods explains how header rules work). That header turns up on three kinds of domain: a writer's name.substack.com address, a publication on its own custom domain, and any domain that forwards to either. A site that only links to a Substack never sends it.

What the 9,600 is made of

Of the 9,653 Substack domains live in our September data, 4,112 are name.substack.com publications and 5,541 are custom domains. To see what those rows are in practice, we loaded 150 at random. 67 were substack.com publications, and 3 more redirected to their owner's custom domain. 59 were custom domains serving a publication. 19 were vanity forwards: 9 custom domains pointing at a substack.com address and 10 pointing at another custom domain. Two no longer served Substack at all, one of them now a gambling page. Call it roughly one domain in eight a forward, and very few gone.

The forwards include real companies. luizalabs.com, the domain of Magazine Luiza's technology arm, redirects in full to luizalabs.substack.com, where Luizalabs publishes Think Labs. For that company the newsletter has taken over the front door.

Sales signal: treat every row as a publication. A company newsletter on a subdomain tells you a content team exists; a forward tells you the newsletter may be the company's main web presence.

Growth or coverage?

The monthly readings are 3,438 in June 2026, 3,831 in July, 4,681 in August and 9,600 in September. That last step is not Substack's growth. 4,095 of the 4,112 substack.com publications we now count were first detected in August, when our crawl started reaching them, and 61.0% of all live domains (5,887) were first seen in August or September. The set of domains we crawl also turns over every month, dead sites out and newly found ones in, and our detection widens over time.

"Four in ten of the domains we count live on substack.com and six in ten on custom domains, and 2,726 of the 2,727 companies we can name come from the custom side. A writer's substack.com address has no company behind it to match." - Elif Arslan, CMO & Co-founder at TechnologyChecker.io

Sales signal: don't build a timing story on this line. Use September's 9,600 as the size of the list and the 5,541 custom domains as the part with a business behind it.

Who the companies are

We matched 2,727 domains to a company. They're small and new. 86.42% of those with a known size have 1 to 10 employees, 10.79% have 11 to 50, and only 6 exceed 1,000. 54.72% were founded in 2020 or later and 34.91% in the 2010s. Substack says it has 5 million paid subscriptions (substack.com/about, checked 26 September 2026). We see publications and that figure counts subscribers, so the two numbers measure different things.

The recognisable names publish from a subdomain beside a main site built on something else. Gainsight runs [Un]Churned at unchurned.gainsight.com, dbt Labs The Analytics Engineering Roundup at roundup.getdbt.com, and the DNC's grassroots team The Blue Print at blueprint.democrats.org. Design studio BUCK, fashion title i-D and Boing Boing do the same.

Sales signal: the core account is a company of under ten people founded this decade, often a consultancy or a media outfit. Larger accounts exist, but for them Substack is one newsletter, so sell to the team that writes it.

Industry and geography

No industry reaches 8%. Technology, Information and Internet leads at 7.88%, and two clusters of about equal size sit on top of the long tail: tech companies at 16.03% (adding Software Development and IT Services and IT Consulting) and media at 15.92% (Technology, Information and Media, Media Production, Online Audio and Video Media, Internet News). Business Consulting and Services (5.45%) and Professional Training and Coaching (3.96%) are the consultants and coaches who write to win work.

The United States has 1,046 matched companies, the United Kingdom 187, India 76, and Canada and Australia 53 each, so those five hold 1,415 of the 2,727. France (52), Spain (47) and the Netherlands (46) sit close behind.

Sales signal: for newsletter tooling, the US and UK are most of the list. For services sold to consultants and coaches, filter on those two industries first.

Why there is no migration table

263 domains have dropped Substack since we began tracking it in March 2026, against 9,600 live, and 41.3% of those were seen only once, which is more flicker than exit. No destination passed our tests. The closest was WordPress: 141 Substack domains dropped WordPress over those months, but 274 of the 450 domains that ever showed both still show both. That reads as a newsletter added beside a site more than a switch. Between Substack and Ghost the moves run 11 one way and 10 the other. 4 domains that dropped Substack now run beehiiv, and 11 that dropped beehiiv still run Substack.

"Fewer than 300 domains dropped Substack in the months we have watched, and for most of them we can't name a destination. I'd rather publish no table than a table of guesses." - Elif Arslan, CMO & Co-founder at TechnologyChecker.io

Sales signal: churn is low and slow, so prospect on need rather than on departures. The WordPress overlap is the better angle: 274 domains run both, a website on one and a newsletter on the other.

What sits beside the newsletter

We measure the stack on the 5,541 custom domains only, because on a substack.com address everything we detect is Substack's own platform. On the custom domains, Google Workspace handles email for 29.42% and Microsoft 365 for 6.71%. GoDaddy (27.4%) and Namecheap (4.42%) show up as DNS provider or registrar. The main websites run on Vercel (5.45%), WordPress (4.94%), Squarespace (2.31%) and Webflow (2.13%), each well under one domain in ten.

Sales signal: more than six in ten of these domains show neither Google Workspace nor Microsoft 365, so business email is still open for most of the base.

What reviewers say

G2 lists only 17 reviews for Substack (4.3 out of 5 on 26 September 2026), and most of its themes rest on a single mention, so we don't publish a pros and cons block. The one theme with two mentions is a complaint about limited features, mostly around monetisation. Seventeen reviews against 9,600 domains fits a base of writers more than of software buyers.

Sales signal: tools that fill Substack's gaps, such as a fuller website or deeper analytics, have an opening. The named list shows the pattern: 43 of the 50 companies publish on a subdomain beside a main site built elsewhere.

Key takeaways

1. 9,600 domains: 4,112 substack.com publications and 5,541 custom domains; 19 of 150 in a live sample were forwards.

2. The September jump is coverage: 4,095 substack.com publications were first detected in August.

3. 2,726 of 2,727 matched companies come from custom domains, and 86.42% have 1 to 10 employees.

4. Tech (16.03%) and media (15.92%) are the two largest industry clusters.

5. No migration corridor passes our tests; 263 domains dropped Substack since March 2026.

How to use this list

Start with the custom domains, read the host column to tell a company newsletter from a main site, and filter on size before industry. For the full list of 9,600 Substack domains with company, size and stack data, explore TechnologyChecker.io.