Vision Block is a free Chrome add-on developed by David Ding that aims to assist web developers in testing screen reader navigation. It provides a visual obscuring feature that encourages developers to rely solely on screen readers to interpret web page content.

Web developers understand the importance of ensuring that their pages and components can be properly interpreted by assistive technology, such as screen readers. However, it can be challenging for developers without visual impairments to resist the instinct to visually inspect their work during testing.

With Vision Block, developers can activate the extension to visually obscure the entire viewport, forcing them to rely on screen readers for interpreting page content. By doing so, developers can gain a better understanding of how users with visual impairments experience their websites.

Overall, Vision Block is a useful tool for web developers who want to thoroughly test the accessibility of their web pages and components. It provides a simple and effective way to encourage screen reader navigation and ensure that websites are accessible to all users.