Change the fonts and colors websites use

https://support.mozilla.org/en-US/kb/change-fonts-and-colors-websites-use

Use themes to change the look of Firefox

https://support.mozilla.org/en-US/kb/use-themes-change-look-of-firefox

Firefox themes

https://addons.mozilla.org/firefox/themes/

File a bug report or feature request in Mozilla products

https://support.mozilla.org/en-US/kb/file-bug-report-or-feature-request-mozilla

Plugins

Text Spacing Editor

https://addons.mozilla.org/en-US/firefox/addon/text-spacing-editor-actum/ (Firefox)
https://chromewebstore.google.com/detail/text-spacing-editor/amnelgbfbdlfjeaobejkfmjjnmeddaoj (Chromium)

Fonts and Dyslexia

Special, free fonts made for dyslexics (such as « Open Dyslexic ») are actually rarely used by those affected or are not very effective. (Source : The Readability Group, https://www.bdadyslexia.org.uk/ or https://culturedys.com/quelle-est-la-meilleure-police-pour-les-dyslexiques/).

The British Dyslexia Association outlines the following principles in conjunction with other accessibility guidelines such as the Web Content Accessibility Guidelines (WCAG). (Sources : https://cdn.bdadyslexia.org.uk/uploads/documents/Advice/style-guide/BDA-Style-Guide-2023.pdf?v=1680514568 and https://www.bdadyslexia.org.uk/advice/employers/creating-a-dyslexia-friendly-workplace/dyslexia-friendly-style-guide)

Readable fonts

• Use sans serif fonts, such as Arial and Comic Sans, as letters can appear less crowded. Alternatives include Verdana, Tahoma, Century Gothic, Trebuchet, Calibri, Open Sans.
• Font size should be 12-14 point or equivalent (e.g. 1-1.2em / 16-19 px). Some dyslexic readers may request a larger font.
• Larger inter-letter / character spacing (sometimes called tracking) improves readability, ideally around 35% of the average letter width. If letter spacing is excessive it can reduce readability.
• Inter-word spacing should be at least 3.5 times the inter-letter spacing.
• Some dyslexic people find that larger line spacing improves readability. It should be proportional to inter-word spacing ; 1.5/150% is preferable.
• Avoid underlining and italics as this can make the text appear to run together and cause crowding. Use bold for emphasis.
• Avoid using all capital letters and uppercase letters for continuous text. Lower case letters are easier to read.

Headings and structure

Use headings and styles to create consistent structure to help people navigate through your content.

• For headings, use a font size that is at least 20% larger than the normal text. If further emphasis is required, then use bold.
• Use formatting tools for text alignment, justification, indents, lists, line and paragraph spacing to support assistive technology users.
• Add extra space around headings and between paragraphs.
• Ensure hyperlinks look different from headings and normal text.

Colour

• Use single colour backgrounds. Avoid background patterns or pictures and distracting surrounds.
• Use sufficient contrast levels between background and text.
• Use dark coloured text on a light (not white) background.
• Avoid green and red/pink, as these colours are difficult for those who have colour vision deficiencies (colour blindness).
• Consider alternatives to white backgrounds for paper, computer and visual aids such as whiteboards. White can appear too dazzling. Use cream or a soft pastel colour. Some dyslexic people will have their own colour preference.
• When printing, use matt paper rather than gloss. Paper should be thick enough to prevent the other side showing through.

Layout

• Left align text, without justification. This makes it easier to find the start and finish of each line and ensures even spacing between words.
• Avoid multiple columns (as used in newspapers).
• Write short simple sentences : 60 to 70 characters is optimal.
• Use white space to remove clutter near text and group related content.
• Break up the text with regular section headings in long documents and include a table of contents.

Writing Style

• Use active rather than passive voice.
• Be concise ; avoid using long, dense paragraphs.
• Write in simple clear language using every day words.
• Use images to support text. Flow charts are ideal for explaining procedures. Pictograms and graphics can help to locate and support information in the text.
• Consider using bullet points and numbering rather than continuous prose.
• Give instructions clearly.
• Avoid double negatives.
• Avoid abbreviations where possible ; always provide the expanded form when first used.
• Provide a glossary of abbreviations and jargon.