Before 2016, a domain-validated certificate typically cost real money every year, which meant a meaningful share of the web — personal blogs, small nonprofits, hobby projects — simply didn't use HTTPS. Let's Encrypt, a nonprofit certificate authority backed by the Internet Security Research Group, changed that by issuing free, short-lived (90-day) certificates through a fully automated protocol (ACME).
Why automation mattered as much as being free
Short-lived certificates only work at scale if renewal doesn't require a human. ACME clients (like Certbot) handle issuance and renewal automatically, which also improved security overall — a shorter validity window shrinks the damage a compromised or misissued certificate can do before it expires.
The effect was industry-wide: browsers began marking plain HTTP sites as "Not Secure," hosting providers began offering free SSL by default, and HTTPS adoption crossed from a minority to the overwhelming majority of web traffic within a few years.
Who founded and backed the Internet Security Research Group
The ISRG was founded with backing from major technology companies including Mozilla, Cisco, and Akamai among its founding sponsors, along with continued support from a broader coalition of sponsors since — this multi-organization backing was significant, since it gave a genuinely free certificate authority the institutional credibility and financial sustainability that earlier, smaller free CA efforts had generally lacked.
How Certbot specifically became the dominant ACME client
The Electronic Frontier Foundation developed and maintained Certbot as the reference ACME client alongside Let's Encrypt's launch, and its combination of broad platform support, active maintenance by a respected organization, and straightforward command-line usability made it the default choice for most server administrators, cementing a close working relationship between EFF and Let's Encrypt's broader mission.
What specific technical hurdles Let's Encrypt had to solve to operate at unprecedented scale
Issuing certificates automatically for potentially any domain on the internet, at a scale no prior CA had attempted, required Let's Encrypt to build genuinely novel infrastructure for automated domain validation, abuse prevention, and issuance rate limiting — solving operational challenges that simply hadn't existed at this scale for any CA relying on traditional, more manual issuance processes.
How Let's Encrypt's success affected the broader CA competitive landscape
Let's Encrypt's rapid growth to become one of the most-used CAs by volume within just a few years forced meaningful strategic responses from established commercial CAs, many of which shifted focus toward higher-validation products, enterprise certificate management tooling, and adjacent services rather than attempting to compete directly on basic DV certificate pricing against a free, well-funded nonprofit alternative.
How Let's Encrypt's nonprofit structure specifically enabled its mission
Operating as a nonprofit, rather than a commercial CA with shareholders expecting returns, let Let's Encrypt prioritize maximizing certificate issuance volume and ecosystem-wide adoption over extracting revenue per certificate — a structural choice directly enabling the free issuance model, since a for-profit CA operating at the same massive scale would have faced very different commercial pressures around pricing.
Its lasting influence on how new internet infrastructure projects get funded and governed
Let's Encrypt's combination of nonprofit governance, broad multi-company sponsorship, and open technical standards has since been referenced as a template for other critical internet infrastructure projects seeking similarly broad, sustainable backing — demonstrating that foundational internet security infrastructure doesn't necessarily require a traditional commercial business model to achieve both financial sustainability and massive, trusted scale.
A closing thought on what Let's Encrypt ultimately proved
Beyond the specific technical and business model innovations, Let's Encrypt's clearest lasting achievement was proving that foundational internet security infrastructure could be both free and trustworthy at massive scale — a combination many in the industry had assumed was fundamentally unsustainable before Let's Encrypt demonstrated otherwise.