HeadingsMap browser add-on, essential for any writing for the web to check your headings are in order.

LanguageTool Grammar and Spell Checker, provides tips in any text editing box (WYSIWYG).

Landmark Navigation via Keyboard or Pop-up, review the landmarks for keyboard navigation.

Stylus, allows you to specify alternative CSS stylesheets for websites. Fiona has used this in workshops to show the effect of copy and pasting from Word, which essentially stops a custom stylesheet to say make the font bigger not work correctly. Custom stylesheets can be specified as reasonable adjustments, and this is also useful for simulating accessibility issues.

WAI Report Generation tools for planning and documenting testing: WAI WCAG-EM (Evaluation Methodology) Tool; Evaluation Methodology Site; WAI ATAG Report Tool (for authoring tools).

W3C Teaching Materials Page, really helpful and adaptable materials for teaching accessibility.

WCAG Color Contrast Checker, same author as HeadingsMap, super helpful for showing issues live in workshops.

WCAG Quick Reference, essential and the filters on the left are really helpful.

Web Developer add-on for Mozilla Firefox - recommended by WAI and can be used to quickly turn off all styles, to get an idea of what a screen reader has to work with on a page. Can also be useful to produce a report of images of a page missing alt text.