Companies Using Caddy

Caddy is a small count, and it says more about platforms than about the companies in it. A domain counts here when the Server header in our crawler's response names Caddy. In our October 2026 crawl that's 68,037 domains, 30,685 of them matched to a company, 6th of 70 in Web Servers with 0.47%. On 12 October I took samples and looked up headers and DNS records by hand, because the header alone doesn't tell you who owns the server.

One in five is a Readymag site

The website builder Readymag is on 19.41% of Caddy domains. Its help centre tells customers to point an A record at 54.194.41.141, and all eight Readymag domains I sampled resolved to that address and answered with a Caddy header. Statsig, a feature-flagging tool, shows on 18.7% of Caddy domains for the same reason: it comes with the Readymag pages. A second builder adds more. 6,190 Caddy domains carry the script set we found on SITE123 sites. I checked 15 of them at random, and 13 were SITE123 sites answering through Caddy; the other two didn't respond. Between them, the two builders account for more than a quarter of the count.

Sales signal: on those sites the web server belongs to the builder, not the company. Don't pitch them hosting or a firewall. Sell what the builder leaves out.

The custom-domain layer

The enterprise rows point the same way. Caddy's On-Demand TLS obtains a certificate the first time a new domain connects, and Caddy's own page calls it the secret sauce of many SaaS products that offer custom domains. Our company list bears that out. Of the 50 detection URLs, 18 are subdomains a software vendor serves for the company. Five are help centres on Help Scout's Docs, Serta's, Transit's and Usborne's among them. Three are partner directories on PartnerPage, for ShipBob, Circle and Lighthouse. Two are affiliate portals on GoAffPro, and AppsFlyer's forms subdomain points at Fillout. Each time, the DNS record points at the vendor and the response comes back from Caddy.

"When a big company turns up on a Caddy list, the first thing I check is the CNAME. Often it points at a SaaS vendor that picked Caddy for its custom-domain certificates." - David Thomson, CTO at TechnologyChecker.io

Sales signal: here the account is the SaaS vendor, not its customer. Help-centre, partner-portal and form vendors running Caddy are prospects for certificate monitoring and edge security.

Lost headers aren't lost customers

The count fell from 74,776 in June to 68,037 in October, with the biggest drop, 7,089 domains, between July (74,254) and August (67,165). Part of that is our side: the domains we crawl turn over every month, with dead sites dropping out and new ones added, and our detection signals widen over time. Since we began tracking it in March 2026, 40,656 domains have dropped the Caddy header, and about 2,700 of them still show it on another hostname. A Server header changes whenever someone adds or removes a proxy, so I don't read those drops as companies leaving Caddy. That's why we suppressed the OpenResty switching rows, the same call we made on our IIS profile.

Sales signal: before you treat a vanished Caddy header as a migration, request the domain again and see what answers. Often it's a proxy change or a dead site.

The companies behind the domains

73.1% of matched companies with a known size have 1 to 10 employees, and 91.96% have 50 or fewer. They're young: 72.05% were founded in 2010 or later, 30.78% in the 2020s alone. Software Development leads the industries at 4.97%, and Design Services (2.42%) makes the top ten. Only 172 companies have more than 1,000 staff, and some of them do run Caddy themselves. Air Liquide's shareholder site answers with Caddy in front of Nginx. Coalfire, Tractebel and Lingoda answer from behind Amazon CloudFront, and the University of North Texas library and Spain's Ministry of Health answer with Caddy directly. Stephen F. Austin State University reports FrankenPHP, a PHP application server that embeds Caddy.

Sales signal: the companies running Caddy on their own infrastructure are the list for observability and PKI tools. Filter out the builder and SaaS rows first, or most of your list won't be yours to sell to.

Europe ahead of the US

The United States has the most matched companies, 6,597, but the ten European countries in our top 15 add up to 11,972, 1.8 times as many. Germany (2,844), the United Kingdom (2,604) and France (1,540) lead them, and Sweden (1,061) and Norway (698) rank above Australia (639). I haven't split the European count by platform, so I can't say how much of that lead is Readymag.

Sales signal: for developer-tool vendors with a European sales team, Caddy's base is a better fit than its 0.47% share suggests.

What runs next to Caddy

Across the 66,265 domains in our clean live set, Readymag is on 19.41% and WordPress on only 7.55%. Next.js is on 5.36%, Ruby on Rails 2.43%, Express 2.39% and Laravel 1.18%. Cloudflare fronts 17.17% and Amazon Web Services hosts 5.89%. Fathom (2.5%) and Umami (1.74%), two privacy-focused analytics tools, show up as well. Caddy's own site credits Fathom for its analytics.

"WordPress on 7.55% of a web server's domains is low. Take out the site builders and what's left leans towards apps that developers deploy themselves." - David Thomson, CTO at TechnologyChecker.io

Sales signal: Next.js, Rails and Express sites behind Caddy are the developer-run segment. That's where API and deployment tools will find buyers.

What Caddy costs

The software is free. Caddy is open source under the Apache 2.0 licence on GitHub, where the latest release is v2.11.7, and its README says it gets certificates from ZeroSSL and Let's Encrypt for public names. The project's income comes from sponsorships, which buy support: $25 a month for an individual, $99 for a startup, $999 for a business and $5,900 for an enterprise. The site's copyright line names ZeroSSL.

Sales signal: you can't undercut a free server on price. What a Caddy shop might buy is help running it: support, monitoring, or someone to take the certificates off their hands.

Key takeaways

1. 68,037 domains, 6th of 70 in Web Servers with 0.47%, counted from the Server header, so a floor.

2. About one in five is a Readymag site, and 6,190 more carry SITE123's script set.

3. 18 of our 50 company rows are subdomains a SaaS vendor serves through Caddy.

4. 73.1% of matched companies have 1 to 10 staff, and 72.05% were founded in 2010 or later.

5. The 40,656 header drops since March are hostname turnover, not customers leaving.

Working with the list

Take out Readymag and SITE123 domains first, then check the CNAME on each enterprise row. For the full list of 68,037 Caddy domains with company and stack data, explore TechnologyChecker.io. Our guide to technology detection methods explains why a header detection can name the platform rather than the site owner.