Plain language and readability for accessibility

Plain language is writing that its intended readers can understand and use. The US Plain Writing Act of 2010 defines plain writing as writing that is clear, concise, well-organized, and follows other best practices appropriate to the subject or field and intended audience (section 3 of the Act). Readability is the narrower idea of how easy a text is to read, which formulas such as Flesch-Kincaid estimate from sentence length and syllables per word. WCAG uses that idea in one criterion, 3.1.5, and touches wording elsewhere through headings, labels, unusual words and abbreviations.

W3C explains that reading disabilities such as dyslexia make written words hard to recognize, and that decoding a text word by word uses mental energy that readers would otherwise spend on understanding it (Understanding 3.1.5). Such readers exist even among highly educated experts. Descriptive headings also help people with limited short-term memory (Understanding 2.4.6).

This guide covers the words on the page. Type size and spacing belong to accessible typography, and the heading outline to our heading structure guide. Nothing here shows that a page meets WCAG or any law.

What WCAG says about wording and reading level

Only one success criterion in WCAG 2.2 mentions a reading level: 3.1.5. Several others bear on how text is written. The table lists the main ones, with the wording shortened.

What 3.1.5 asks for

W3C defines the lower secondary education level, using UNESCO's International Standard Classification of Education, as 7 to 9 years of school, and says supplemental content is needed when text demands more than nine years (Understanding 3.1.5). The criterion is met by writing at that level or by offering something extra: a text summary at that level (G86), illustrations (G103), a spoken version (G79), easier text (G153) or a sign language version (G160). Proper names and titles are set aside before assessment. W3C's reasons are that names cannot be shortened without making sentences harder to understand, and that rewording a title would leave readers unable to tell what it refers to.

3.1.5 is Level AAA, and W3C does not recommend requiring AAA conformance as a general policy for entire sites, because some content cannot satisfy every AAA criterion (WCAG 2.2, conformance requirements). Our conformance levels guide explains each level. In our reading, that is no reason to skip the criterion where a reader must act on the text: instructions, forms, pricing, eligibility and policy pages.

Writing for your audience and the WCAG line

Digital.gov and WCAG start from different places. The US Government's plain language guide on Digital.gov is adapted from PlainLanguage.gov. Its principles page says the first rule is to write for your audience, calls the idea that you must "dumb down" content a myth, and says to write for eighth graders only if they are your audience. WCAG 3.1.5 sets a fixed line instead, because difficult text may suit most of a readership while people with reading disabilities still exist among experts. The two fit together: write in the plainest words the subject allows, and where the result still runs above the lower secondary level, add a summary or another aid.

Plain language rules that work on a web page

Three sources cover much of the same ground: W3C's technique G153, Making the text easier to read, the Digital.gov guide, and W3C's cognitive accessibility note, a 2021 Working Group Note that is not required for WCAG conformance. Each point below names the source it comes from.

• One idea per sentence. Digital.gov says to express one idea in each sentence (clear and short). G153 asks for simple sentence forms, no more than two conjunctions, and sentences no longer than the typical length for secondary education, which it gives as 25 words in English.
• One topic per paragraph. Digital.gov cites experts who recommend paragraphs of no more than 150 words in three to eight sentences, and says each should open with a topic sentence.
• Common words. G153 says to avoid jargon and slang and to replace long or unfamiliar words with shorter ones. Digital.gov's familiar terms list pairs "use" with "utilize" and prefers "must" to "shall" for a requirement.
• Active voice, present tense, literal wording. Digital.gov says passive voice hides who does what and present tense is the simplest verb form (writing for understanding). The cognitive accessibility note agrees, and asks for literal, concrete language with an explanation wherever a metaphor or simile appears.
• Positive wording. Digital.gov's style page says negative wording is harder to process, a double negative can reverse the meaning, and a slash, as in "and/or", leaves the decision to the reader.
• Lists, consistent names and key information first. G153 prefers lists to long comma-separated series and asks for consistent names and labels. Digital.gov's design page asks for key information at the top.

The rewrites below are invented examples. The rule behind each comes from the sources above.

Headings and labels

Success criterion 2.4.6 asks that headings and labels describe topic or purpose. W3C says they need not be long: a word, or even a single character, may be enough if it gives an appropriate cue. The criterion is separate from 1.3.1: a heading can describe its section well and still not be marked up as a heading, and a real heading element can fail 2.4.6 if its words say nothing (Understanding 2.4.6; see also our 1.3.1 page).

Digital.gov describes three kinds of heading: question headings, which suit pages that answer questions readers already ask; statement headings, which are specific and direct; and topic headings, the most formal, which can be so vague that they are not helpful. A quick test, in our reading, is to read only the headings, top to bottom. W3C's writing tips say good headings give an outline of the content, so if yours does not tell the page's story, rewrite them.

The same standard applies to labels, instructions and error messages. 3.3.1 requires an automatically detected input error to be described in text and 3.3.3 requires a suggested correction where one is known, and W3C's writing tips ask for error messages that say what the problem is and, where possible, how to fix it. Our guides to accessible forms, error messages and link text cover those cases, and the 2.4.4 page covers link wording.

Jargon, abbreviations and idioms

Criteria 3.1.3 and 3.1.4, both Level AAA, ask for a way to find what unusual words and abbreviations mean. W3C's note on 3.1.3 encourages authors to meet it for specialized information aimed at non-specialist readers, even when claiming only A or AA. W3C's techniques include an inline definition at first use (G112, with the HTML dfn element), a link to a definition (G55), a glossary (G62) and, for an abbreviation, the expanded form next to its first use (G97). Abbreviations that have become ordinary words, such as laser, are exempt.

W3C lists screen magnifier users among those who benefit, because magnification removes surrounding context, which in our reading argues for putting a definition next to the term. For everyday writing, Digital.gov suggests a short name in place of an abbreviation where you can, and no more than three, preferably two, abbreviations in one document (style).

Measuring readability, and what a formula misses

WCAG says to measure but not how. Technique G153's test has two steps: measure the readability of the text, then check that it needs less than the lower secondary level. Neither G153 nor the 3.1.5 Understanding page names a formula or a score, and the Understanding page says qualified teachers can evaluate text against local education standards.

Word's built-in statistics are one place to start. Microsoft's support page says Word reports two Flesch tests, Reading Ease and Flesch-Kincaid Grade Level, and that both rest on the average number of words per sentence and syllables per word. Its targets for most documents are a Reading Ease score of 60 to 70 and a Grade Level of about 7.0 to 8.0. Those are Microsoft's numbers, not WCAG's.

Because the Flesch formulas count only sentence length and syllables, they miss what often makes text hard. In our reading:

• A short word that few readers know, or an unexplained abbreviation, scores as easy, and a clear sentence with a long product name scores badly. W3C's criterion sets proper names aside for a related reason: they cannot be shortened.
• A formula cannot tell whether the order is logical, whether a heading describes its section or whether an instruction says what to do next.

W3C states the limit itself: its working group could not find a way to test whether the clearest, simplest language had been achieved, so it used reading level to make the criterion testable.

For a better test, ask readers. Digital.gov's test for understanding describes paraphrase testing, where people restate the content in their own words, which suits short pages and survey questions, and usability testing, which suits longer documents, sites and forms. It advises testing early and at least twice, revising after each round. Where you can, include people with reading or cognitive disabilities among the testers. The cognitive accessibility note covers including users in research, design and testing; neither it nor WCAG requires it.

Where to start on a real site

In our reading, start where wording costs a reader a task: forms, instructions, error messages and checkout. Summarize long documents at the start, as Digital.gov's principles advise; G86 and the cognitive accessibility note describe a summary in plainer words, and the note says media files should have a summary too, which includes video and audio and their transcripts. Readable wording also needs a layout that survives magnification: see zoom and reflow.

Plain language and the law

The US Plain Writing Act of 2010 requires federal executive agencies to use plain writing in the covered documents they issue or substantially revise (sections 3 and 4). It provides for no judicial review and creates no enforceable right (section 6). It applies to agencies, not to private websites.

The web accessibility rules we track point to WCAG at Level AA or below, and 3.1.5 sits above that: the ADA Title II web rule uses WCAG 2.1 Level AA, and the Revised Section 508 Standards incorporate WCAG 2.0 Level A and AA for federal agencies. Our pages on US law, Section 508 and EN 301 549 give the detail. This is general information, not legal advice.

Check it yourself

Tools can check structure and give a rough score. They cannot judge whether your words work.

• Heading outline. The free heading checker lists every H1 to H6 on a page, draws the outline and flags a missing or repeated H1, skipped levels and empty headings. It does not judge the words, so read the outline against 2.4.6. The accessibility bookmarklet checks a live page in your browser.
• Link wording. The link text checker lists every link with the name a screen reader announces and flags vague text such as "click here".
• Readability score. Turn on readability statistics in Word, using the steps on Microsoft's support page, and treat the result as a rough screen.
• Tracking. The WCAG audit checklist lets you choose a Level AAA target, so 3.1.3, 3.1.4 and 3.1.5 appear beside 2.4.6. Record a result and notes for each, and export a CSV.
• Automated scan. Scan my site for free runs 16 rule-based checks on your page's HTML, including headings and form labels. None of them judges how easy your sentences are to read, as what we check explains.

A clean result on any of these does not show that a page is easy to read or that it meets WCAG. The WCAG 2.2 criteria reference lists every criterion.