cloudparts

Readable

A hosted readability service, with an HTTP API, that scores text or a web page with 15 readability formulas, CEFR and IELTS levels, an A–E rating, tone and sentiment, and highlights long sentences, passive voice, clichés and hedge words.

What it is
Linters, formatters and type checkers (prose linters)
Type
Commercial product
Made by
Readable
License
Proprietary
Facts checked
23 October 2026
Website

What it is

Readable is a web app for writers and marketers, and its API lets other software ask for the same scores. You POST plain text to /api/text/ or a URL to /api/url/ (optionally extracting just the body copy), and get back JSON with Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog, Coleman-Liau, SMOG, Automated Readability Index, Dale-Chall, Spache and other formulas, CEFR and IELTS levels, and Readable’s own A–E rating. It also returns word, sentence and syllable counts, reading and speaking time, keyword density for one- to three-word phrases, and 0–100 scores for sentiment, tone (formal to informal), personalism and gender.

A second call, /highlight/, returns the problems behind a score for six hours after scoring: long and very long sentences, hard words, adverbs, clichés, passive voice, hedge words, buzzwords and profanity; /profanity/ checks text at three sensitivity levels. Requests are signed rather than carrying the key: each sends the current UNIX time and an MD5 hash of the API key plus that time, and requests more than 30 seconds old are rejected. A test key returns real-shaped results for a fixed sample text at no charge. The API is sold on Readable’s AgencyPro plans.

Why teams pick it

  • Many readability formulas in one call, so you can match whatever metric a client or regulator asks for
  • Scores whole web pages by URL, with optional extraction of the main body copy
  • Highlights explain a score sentence by sentence, not just a number

Watch out for

  • Closed source and hosted: text is sent to Readable’s servers, and API access needs the AgencyPro plan
  • Readability formulas measure sentence and word length, not whether the text is accurate or well organised
  • No style-guide rules of your own; for house terminology or CI gating, an open-source linter such as Vale fits better
  • Requests are signed with an MD5 hash, and the docs publish no rate limits or API prices

Alternatives

What all prose linters have in common →Compare side by side →
alexDormantOpen sourceA Node.js linter that flags gendered, ableist, condescending or profane wording in Markdown, MDX, HTML and plain text, and suggests neutral alternatives.ValeOpen sourceA command-line linter for prose: it parses Markdown, AsciiDoc, HTML and code comments, then checks the text against style rules written as YAML files.

Scoring text with the API (request signing as documented) · bash

T=$(date +%s)
SIG=$(printf '%s%s' "$READABLE_KEY" "$T" | md5sum | cut -d' ' -f1)

curl -X POST https://api.readable.com/api/text/ \
  -H "API_REQUEST_TIME: $T" -H "API_SIGNATURE: $SIG" \
  --data-urlencode "text=The quick brown fox jumps over the lazy dog."

# JSON with result, score_id, rating (A-E), flesch_reading_ease,
# flesch_kincaid_grade_level, gunning_fog_score, word_count, sentiment, tone, ...

See it in a real stack

No architecture uses Readable yet. Drop it into the playground and wire it up yourself.Open playground →
Where it came from2015–2019

Founder Dave Child started readability-score.com in 2015 after coming across Rudolf Flesch’s Reading Ease formula. The company moved to readable.io in 2016, deciding the old name was “ironically hard to read”, launched the paid ReadablePro service in 2018 and settled on readable.com in 2019, where it now sells tools for documents, websites and software, the last through the API.

Why it’s built this way

Report many formulas instead of one
Each formula weighs sentence, word and syllable length differently; returning them all lets users pick the measure they already use, and the A–E rating sums them up in one grade.
Sign requests instead of sending the key
The key never travels with a request, and the 30-second time window stops a captured request from being replayed later.

Timeline

  1. 2015

    readability-score.com launched

  2. 2016

    Moves to readable.io

  3. 2018

    ReadablePro launches

  4. 2019

    Moves to readable.com

Sources3 · facts checked 23 October 2026

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