Readability

Readability is an open-source tool that analyzes Markdown files for readability scores and content thresholds. It best suits writers and documentation teams who want repeatable checks in a development workflow. Its strength is configurable analysis across local and CI workflows; it does not rewrite prose or judge whether it is sound.

Overview

Readability combines several grade-level formulas with reading-ease, estimated reading-time, and word and sentence metrics. That makes it useful for spotting shifts in complexity across documentation, especially when a team wants consistent criteria rather than a single score. But these measures address word and sentence complexity only: they cannot establish accuracy, completeness, context, or tone.

Key features

Scoring and content checks

The tool reports Flesch-Kincaid, Gunning Fog, Coleman-Liau, SMOG, and ARI grade-level scores, plus reading ease and estimated reading time at 200 words per minute. It can also measure word and sentence metrics and detect or require MkDocs-style admonitions. The mix is practical for teams setting both readability and documentation conventions, but users seeking plain-language rewrites or accessibility guidance will need another tool.

Thresholds and workflow

Configurable thresholds can fail a CI check when documentation exceeds chosen limits, making regressions easier to catch before changes ship. A .readability.yml file supports path-specific overrides, while a JSON Schema enables editor validation and autocomplete. Users can run the Go command-line tool, Docker image, GitHub Action, pre-commit hooks, or build from source. The project also documents CI/CD examples for GitLab CI, CircleCI, and Jenkins.

The GitHub Action can run checks in workflows and add a formatted report to the Actions job summary. Outputs include table, Markdown, JSON, summary, and report formats, so teams can choose between a quick result and a more structured artifact. Docker images are documented as Cosign-signed, with a signed SBOM and a distroless base image running as a non-root user.

Pricing

Readability costs nothing. The free plan includes the MIT-licensed GitHub Action, CLI, and Docker image, and no paid plans are listed. There is no cheaper tier with reduced features to weigh against a paid upgrade; the relevant trade-off is whether its focused Markdown analysis covers your needs. The MIT license also identifies it as open source.

Platforms

Readability supports Linux, macOS, and Windows. Pre-built binaries are listed for Linux and macOS in amd64 and arm64 versions, while the documented Windows binary is amd64 only. That distinction matters for Windows users on arm64 devices, who should not assume a matching pre-built binary is available.

Who it's for

Bloggers, technical writers, documentation teams, students, and curious readers can use Readability to examine prose complexity. Its strongest fit is a team that wants consistent thresholds and CI enforcement for Markdown documentation. It is less suitable for people who need automated rewrites, accessibility recommendations, or editorial judgments beyond measurable complexity.

Pros and cons

• Pros: Five grade-level formulas plus reading ease and estimated reading time give teams multiple ways to track complexity.
• Pros: Thresholds, path-specific overrides, and CI integrations support repeatable checks across documentation workflows.
• Pros: Free, open-source tooling spans CLI, Docker, GitHub Action, and pre-commit use.
• Cons: It analyzes Markdown rather than offering plain-language rewrites or accessibility guidance.
• Cons: Scores cannot assess accuracy, completeness, context, or tone, so they cannot replace editorial review.
• Cons: The documented pre-built Windows binary is amd64 only, unlike the amd64 and arm64 binaries listed for Linux and macOS.

Alternatives

For a broad directory of AI-focused tools, browse AI Readability Checkers. Choose ToolsVale Readability Checker if you want a free option spanning mobile, desktop, and web platforms. APIVerve Website Readability API is an alternative for API and web use, with a free tier of 200 credits per month, a five-request-per-minute limit, non-commercial use, and attribution required.

Eclipse Readability Studio is another free, open-source option for Linux, macOS, and Windows. For a Python package with an MIT license, consider textstat. Readability Formulas offers free online readability tools alongside extension, macOS, web, and Windows platforms. A2Z Tools Plain Language Analyzer is a free web tool limited to English. PageRefine is a free web tool with no signup. ProfText offers a free tier with 5,000 characters per analysis, 30 clarity rules, AI-generated text detection, and unlimited analyses, but no citation verification.

Verdict

Choose Readability if you need free, configurable readability checks for Markdown in local or CI workflows. Its varied scoring methods and threshold enforcement are useful for keeping documentation complexity in view. Look elsewhere if you need rewriting, accessibility guidance, or a judgment of meaning and content quality rather than a measure of sentence and word complexity.