ProseScore analyzes your writing with 8 readability formulas (Flesch-Kincaid, Gunning Fog, Coleman-Liau, SMOG, ARI, Dale-Chall, Spache, Linsear Write), plus sentiment analysis, keyword extraction, and SEO scoring. Everything runs client-side in your browser — your text never leaves your device. Free tier gives you the core score and stats. Pro ($3.99/mo or $19.99 lifetime) unlocks all 8 formulas, sentiment, keywords, SEO, markdown export, and analysis history. Built with textlens.