Readability

Vale rules for the common readability scores: Automated Readability Index, Coleman–Liau, Flesch–Kincaid, Flesch reading ease, Gunning fog, LIX, and SMOG, with a rule that names the polysyllables behind them.

Install

Requires Vale 2.13.0 or later.

StylesPath = styles
Packages = Readability

[*.md]
BasedOnStyles = Readability

$ vale sync

Every score is on by default and grades the whole document, with the alert on line one. Keep the score you care about and turn off the rest, or raise a limit:

[*.md]
BasedOnStyles = Readability
Readability.SMOG = NO
Readability.LIX = NO
Readability.FleschKincaid[condition] = "> 10"

Rule	Flags a document whose
AutomatedReadability	Automated Readability Index is above 8
ColemanLiau	Coleman–Liau grade is above 9
FleschKincaid	Flesch–Kincaid grade is above 8
FleschReadingEase	Flesch reading-ease score is below 70
GunningFog	Gunning fog index is above 10
LIX	LIX score is above 35
SMOG	SMOG grade is above 10

Polysyllables reports each word of three or more syllables, the words behind the SMOG and Gunning fog scores. It is a suggestion, so it shows with MinAlertLevel = suggestion, or when a setting turns it up while you bring a score down:

Readability.Polysyllables = warning

Grading by paragraph

On Vale 3.22.0 or later, a score can be scoped so that the alert lands on the paragraph that reads hard rather than on line one:

[*.md]
BasedOnStyles = Readability
Readability.FleschKincaid[scope] = paragraph
Readability.SMOG[scope] = paragraph

Development

./test.sh runs the cases in tests/ with vale test --coverage, then checks fixtures/page.md against the golden file in testdata/ and requires its rewrite in fixtures/clean/ to pass clean. ./test.sh -u rewrites the golden file.