What is CWAC

The Centralised Web Accessibility Checker (CWAC — pronounced ‘quack’) is software created by the Government Chief Digital Officer (GCDO). It’s designed to scan websites for potential web accessibility issues.

Web accessibility is about making web content that disabled people can use.

What is web accessibility? — Web Accessibility Guide

CWAC’s automated testing primarily focuses on detecting failures to meet the Web Content Accessibility Guidelines (WCAG) 2.2.

This is the international standard that forms the basis of the New Zealand Government Web Accessibility Standard.

Web Content Accessibility Guidelines (WCAG) 2.2 — W3C

NZ Government Web Accessibility Standard

CWAC is open-source software and free for anyone to use.

CWAC GOVTNZ — GitHub

How we’re using CWAC

Starting June 2025, the GCDO is using CWAC to test a range of publicly facing government websites. The results from these scans will be published on Data.govt.nz.

This helps to inform the: 

• agencies’ efforts to improve the accessibility of their websites
• support the GCDO provides agencies in this space.

CWAC monitoring programme

Automated accessibility testing

Automated accessibility testing addresses just a small part of WCAG requirements. A web page that passes all automated accessibility tests does not necessarily conform to WCAG. Assessing WCAG conformance always requires manual testing.

However, automated testing is a reliable, repeatable and low-cost way to gather consistent results about accessibility issues that can be detected by software. It should be used throughout every stage of the design, development and maintenance lifecycle.

What CWAC tests

Axe-core audit

CWAC primarily uses the free and open-source axe-core accessibility engine. Axe-core tests web pages for WCAG failures that can be detected automatically. The axe-core rules are especially useful as they do not raise false positives.

axe-core dequelabs — GitHub

Failures raised by axe-core are categorised by impact by Deque, the company behind the axe-core ruleset.

Issue impacts axe-core dequelabs — GitHub

Other tests

Language audit — text readability

This test provides grade level averages for each web page as calculated by the Flesch-Kincaid and Simple Measure of Gobbledygook (SMOG) algorithms. These averages are a way of estimating how easy it is to read a piece of text. In each case, a score around 8 or lower is recommended.

Flesch-Kincaid readability tests — Wikipedia

SMOG — Wikipedia

CWAC attempts to find passages of text that make sense to test for readability. It only tests paragraphs, list items and headings if there are at least 10 sentences in total and 200 or more words.

The language audit results are indicative only. Manual verification is still required.

Reflow audit

This is a test against WCAG 2.2 Success Criterion (SC) 1.4.10 Reflow. It checks that web pages do not scroll horizontally on narrow screens at a width of 320px.

WCAG 2.2 Success Criterion 1.4.10 Reflow — W3C

The reflow audit results are indicative only. Manual verification is still required.

Focus indicator audit

The focus indicator test checks for the presence of changed pixels on the page when interactive elements receive keyboard focus. This is a requirement of WCAG 2.2. SC 2.4.7 Focus Visible.

WCAG 2.2 SC 2.4.7 Focus Visible — W3C

This is a resource intensive test as it works by comparing screenshots from before and after an element received focus. Keyboard focus is simulated by programmatic pressing of the Tab key. The number of times the Tab key is pressed can be set by the user, limiting and controlling how many screenshots are taken per page. This also limits how many interactive elements on the page are tested for focus indicators.

A failure of the focus indicator audit is reliably a failure of WCAG 2.2 SC 1.4.7 Focus Visible. However, passing the audit does not mean the page as a whole passes SC 1.4.7 — unless CWAC was set to test every focusable element on the page.

Multiple viewport sizes

CWAC can test web pages at different viewport dimensions. This is to support the fact that individual web pages can display different content depending on the size of the browser window. For example, a large browser window might display content in a sidebar, while the same content is hidden behind a menu on a mobile device.

By default, CWAC tests each web page as 2 viewport sizes:

• small — 320 by 450px
• medium — 1280 by 800px.

Contact the team

If you have any questions related to CWAC or the Web Accessibility Standard, email web.standards@dia.govt.nz.