axe DevTools: Deque’s extension for catching accessibility issues while you build

Once installed, the extension sits in the browser’s developer tools, next to the Elements and Console tabs. It analyzes the page code as the browser has built it, including content added by JavaScript, pages behind a login and sites running locally, without sending anything to a server. Results are sorted by severity, from critical to minor. Click an issue and it is highlighted on the page, with its CSS selector, the WCAG rule involved and a help page. You pick the target standard, WCAG 2.0, 2.1 or 2.2 at level A, AA or AAA, and can add “best practices” that go beyond the guidelines. The full version runs in Chrome and Edge; the Firefox version is more limited and doesn’t get the paid features.

Everything rests on axe-core, an open-source JavaScript library (MPL 2.0 license) that Deque has published since June 2015. According to Deque, it automatically finds 57% of WCAG issues on average and only reports definite defects, which is why so many tools use it: Google picked it in 2017 for the accessibility audits in Lighthouse. The rest, what a machine can’t decide on its own, is the job of the Intelligent Guided Tests in the Pro version: the extension asks you questions about the page (is this image decorative? does this table have proper headers?) and turns your answers into a report. With these guided tests, Deque claims up to 80% of issues detected.

The company behind the tool is Deque Systems, founded in 1999 by Preety Kumar, who still runs it. It is based in Herndon, Virginia, with offices in Utrecht and Hyderabad. A digital accessibility specialist, Deque also sells audits, training (Deque University) and a monitoring platform. The product was called WorldSpace Attest until May 2020, when Deque brought its software together under the axe brand; the Pro plan arrived on March 1, 2021. Deque reports more than 400,000 weekly active users for its extension.