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Purple HATS

Purple hats - Sample Screenshot Dark

Purple HATS is a customisable, automated web accessibility testing tool that allows software development teams to find and fix accessibility problems, to ensure all users have access to inclusive digital services, especially the elderly and persons with disabilities (PWDs). It is an open-sourced solution to automate periodic tasks and the testing of government digital services.

Innovation Summary

Innovation Overview

With information and transactions increasingly being shared on and conducted in the digital sphere, it is imperative for digital services to be accessible to and inclusive of all users, especially the elderly and persons with disabilities (PWDs). This challenge inspired a group of passionate Singapore public service officers, one of whom has low vision, to find a way to make Singapore’s digital services more digitally inclusive.

The open-sourced Purple HATS tool was developed by GovTech’s Accessibility Enabling (A11y) Team, to enable software development teams to build more inclusive digital services products in a systematic way. Purple HATS runs a bot that scans through webpages and analyses the markup language that displays webpages. For example, the bot will check:

  • Whether buttons are properly labelled and how those buttons are read by screen readers. If a button is incorrectly labelled or given a generic label (e.g. just ‘button’), a screen reader user will not be able to understand what the button does.
  • Whether pictures or images are labelled correctly, with alternate text (alt text) provided. The absence of alt text causes these pictures to be flagged as an accessibility issue.

The bot then scores the impact of the identified accessibility issue using the open-sourced AXE accessibility testing engine by Deque Systems, a company that provides digital accessibility audits and software tools. Purple HATS results are compiled in JSON format, after which a HTML report is generated. The scoring system has been augmented with a local factor that allows for more fine-grained categorisation of accessibility problems, reflecting whether an accessibility issue is regarded as an existing functional issue by elderly and PWD users in each contextual inquiry. Thus, the results generated by Purple HATS enables software development teams to prioritise their accessibility fixes based on the specific needs of affected users (e.g. low vision, deaf-blind, colour blindness, mobility, sighted keyboard user).

Key Features:

  • Automated testing tool – identifying potential accessibility issues at the code level with choice of sitemap or website scans
  • Scan result reports in JSON and HTML formats – report contains description, link to Web Content Accessibility Guidelines (WCAG), a code snippet of the affected page and a help link (please refer to provided visuals)
  • Purple HATS can be used as a standalone tool, and can also be seamlessly incorporated into a software development team’s CI/CD process.

This grassroots initiative aims to bring digital accessibility considerations to the forefront of the development of Singapore’s government digital services. It also aims to improve the internal digital accessibilities capabilities of the government as part of Singapore’s SmartNation ambitions, to provide citizens with inclusive digital services. The GovTech A11y Team is actively working towards institutionalising accessibility testing as part of the Singapore government’s software development process.

Innovation Description

What Makes Your Project Innovative?

Traditionally, it can be time-consuming and costly to conduct regression testing. Purple HATS automates code-testing of digital services across various web browsers to identify code-level issues so that they can be immediately rectified. It is the first tool of its kind to be developed in-house by the Singapore public service.

What is the current status of your innovation?

Technology alone cannot solve accessibility and inclusivity challenges. The GovTech A11y Team was formalized in 2022 to drive the Singapore government’s efforts to make its digital services accessible, in support of the government’s Enabling Masterplan 2030. The GovTech A11y Team supports the Singapore government in four (4) main areas: consultancy, education and thought leadership, digital policy reviews, and developer tools like Purple HATS.

Innovation Development

Collaborations & Partnerships

The GovTech A11y Team reached out to citizens and fellow public servants to ascertain their pain points. Co-creating with the community enables the GovTech A11y Team to determine how a tool like Purple HATS could best support its users’ needs. Open-sourcing Purple HATS means that both public service officers and private companies can use it when designing and testing their digital services.

Users, Stakeholders & Beneficiaries

See “Innovation Overview” section.

Innovation Reflections

Results, Outcomes & Impacts

Purple HATS was first piloted during a government digital service bug bounty in 2020; GovTech used it successfully to identify bugs across active, public-facing government digital services. The respective product teams were notified of the bugs, and were then able to rectify them within the year. While it originated in GovTech, Purple HATS can now be used by any software development team across Singapore’s public service.

The GovTech A11y Team continues to independently monitor the accessibility of public-facing government digital services, and works directly with product teams to address their accessibility needs. As part of the Enabling Masterplan 2030, the Singapore government aims to make 100% of its high-traffic websites accessible by 2030.

Challenges and Failures

The findings are technical and it may be difficult for non-practitioners of software development to understand them. The GovTech A11y Team continues to iterate to make the test results easier for users to understand, through using simple, didactic language and by laying out the information clearly (please refer to the attached visual).

Education and awareness are also ongoing challenges, and the GovTech A11y Team is working on a slew of activities to engage public service officers at different levels. At the same time, the GovTech A11y Team also collaborates with large private tech organisations to share best practices in the digital accessibility space.

Conditions for Success

A tech solution requires firm policy in place to garner resource as well as guidance to recognise the important of accessibility testing at the forefront.


Manual testing is laborious, and we hope open-sourcing Purple HATS will make its integration and use for testing easier. Ultimately, we see the tool as a medium for influence – as has been experienced by GovTech’s product teams, such as Notarise and Ministry of Trade and Industry’s GoBusiness platform.

Lessons Learned

We’ve learnt much from the elderly and PWDs through contextual enquiry, and have used this feedback to improve the effectiveness of Purple HATS over time. Further, we learnt that inclusivity is a team sport. Some might see ‘accessibility’ as a challenge, but we see it as an innovation opportunity. With a bit of thought and consideration, it is very possible to design and develop digital services that are inclusive in nature. Instead of asking yourself, “Why?”, ask yourself, “Why not?”

Anything Else?

Purple HATS has been listed in the Digital Public Goods registry by the Digital Public Goods Alliance (DPGA). The DPAG is an initiative jointly supported by the current co-hosting entities, the Norwegian Agency for Development Cooperation (Norad), UNDP, and UNICEF.

Supporting Videos


  • Diffusing Lessons - using what was learnt to inform other projects and understanding how the innovation can be applied in other ways

Innovation provided by:


Date Published:

3 January 2023

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