Author - Pauline Mialhe, COO of Happo (Last updated May, 19 2025)

Joe Lencioni helped bring accessibility into the mainstream long before laws required it. Now his new tool could help the rest of us catch up.

A quiet test in 2023

Late 2023. Joe Lencioni is running a test.
On the screen, colors flash:
482 critical accessibility violations, detected instantly on the latest version of his product.

What could feel like a disaster instead feels like clarity.

“It felt like putting on glasses for the first time.”

Joe is co-founder of Happo, a tool originally built for screenshot testing. The feature he just tested is new: an accessibility regression system called <A11y/> by Happo.  Its goal? Make accessibility visible, actionable, and part of the day-to-day development flow.

For Joe, it’s more than a feature. It’s the continuation of a journey that started almost a decade ago.

Back to Airbnb, 2016

In 2016, Joe was working as a frontend engineer at Airbnb. Accessibility in tech was not a hot topic. There were few tools, little awareness, and even less integration in developer workflows.

That’s when Ethan Cohen at Twitter began developing eslint-plugin-jsx-a11y, a plugin for ESLint that would help surface accessibility issues directly in the code editor or review process. Joe helped shape the early thinking and gave the open source project visibility across teams and beyond Airbnb.

“Ethan did most of the implementation. I mostly advised him in the beginning and also gave it a lot of exposure and distribution.”

The plugin became a silent giant. Today, it's downloaded over 16 million times per week. Without buzz, without marketing — just by being genuinely useful.

Although this plugin catches many accessibility issues, a static analysis approach can only take you so far since it is typically scoped to a single file at a time and doesn't have access to the full context that's on the page. Additionally, it is only useful for JSX, so if you aren't using something like React to build your UI, then you are out of luck.

From open source to product design

Years later, Joe left Airbnb to build Happo, a tool that helps teams catch visual bugs through automated screenshot testing. The core principle behind Happo was always the same: surface important issues in a way that’s visible and frictionless.

Eventually, Joe realized this principle applied perfectly to accessibility too. That’s how <A11y/> by Happo was born as a natural extension of Happo’s mission.

What is <A11y/> by Happo? <A11y/> by Happo helps teams build accessible interfaces by detecting accessibility violations as they appear — and before they ship. Powered by Axe by Deque, the system analyzes rendered components and pages, surfacing violations directly inside pull requests.

Key features include:

• Automatically track accessibility violations across your product.

• Get alerts in each pull request when accessibility issues are introduced or fixed.

• See your team’s progress over time — how many violations you’ve fixed, and what’s left to improve.

• No need to write new tests — the tool reuses the components you’re already testing visually.

The Happo team has been using <A11y/> internally throughout its development. On the first run, they found 994 accessibility issues — 430 of them critical. Within a week, most were fixed. And because the testing is continuous, those improvements are now locked in.

“We found that it actually made fixing accessibility issues fun.”

Why now? The EAA is coming

The timing for <A11y/> couldn’t be better. Starting June 2025, companies operating in the EU will be required to comply with the European Accessibility Act (EAA). That means digital interfaces must meet accessibility standards, and organizations must be able to report on their level of compliance. Happo’s approach isn’t about compliance checklists. It’s about integrating accessibility into the way teams already work, making accessible code the default. type: entry-hyperlink id: 1OiXY2XnJLuGoD8EWuiJq8

Making accessibility feel natural

Happo’s team believes accessibility should feel like any other part of quality development: expected, visible, and part of the review process. That belief has guided every feature of <A11y/>, from the interface to the integration.

As Joe puts it:

“Over the last decade, accessibility testing has never felt this easy, frictionless, and integrated.”

Learn more

To read about the law on: The EAA comes into effect in June 2025. Are you ready?
To see how <A11y/> by Happo works in real time, you can watch the launch webinar on LinkedIn.
To try it yourself, visit happo.io.