Matt Holt

Matt Holt is an American software developer best known as the creator of Caddy, the open-source web server written in Go that turns on HTTPS automatically by default. He works on Caddy full-time, funded by sponsorships from companies that rely on it.

Holt started building Caddy in 2014 to make secure, automatic HTTPS the default rather than an afterthought, and released it in 2015. Before that he had already written Papa Parse, a widely used in-browser CSV parser, and he later created CertMagic, the Go library that powers Caddy's certificate automation, along with small developer utilities such as JSON-to-Go and curl-to-Go. He holds a master's degree in computer science.

Keeping Caddy alive was not easy. When the project outgrew what he could handle around 2016, he received an award from Mozilla that let him work on it full-time for about six months. He then tried monetizing commercial users with professional services and a licensing plan for custom binaries, but by his own account that model did not reach sustainability, and the project came close to shutting down when he started graduate school. A rewritten Caddy 2 shipped in 2020, with Ardan Labs as the project's support contractor.

In 2020 ownership of Caddy and CertMagic passed to apilayer, which became the premier corporate sponsor. The license stayed Apache 2.0 and Holt kept leading development full-time. Caddy's sponsor page now asks every professional and business user to sponsor the project, and conference bios list companies such as Stripe, Framer and Mercedes-Benz among its sponsors. The main repository has passed 78,000 GitHub stars.

Alongside Caddy, Holt builds Timelinize, an open-source personal archival suite that pulls photos, messages, locations and other data onto a single private timeline on your own computer. He speaks often about the economics of open source, including a talk titled The Asymmetry of Open Source.

He matters because Caddy helped make HTTPS-by-default normal, and because his long, public search for a funding model is one of the most honest case studies of sustaining critical open source.