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6/26/2026
Developer builds free AI grammar

Developer builds free AI grammar

Original: I Built a Free AI Grammar Checker That Runs Entirely in the Browser

Short summary

A developer built a free, browser-based grammar checker using DeepSeek's API—costing roughly 1/10th of GPT-4o while achieving 91% error detection accuracy. The tool provides sentence-by-sentence corrections, readability scoring (Flesch + CEFR levels), style polish, and tone detection, all running client-side for privacy. The implementation uses vanilla JavaScript and Cloudflare Workers, demonstrating a practical pattern for cost-effective LLM-powered applications.

  • •Free browser-based grammar checker using DeepSeek API at 1/10th GPT-4o cost
  • •Includes sentence corrections, readability scoring, CEFR levels, tone detection—all client-side
  • •Vanilla JS + Cloudflare Workers architecture; $2/month API cost at scale

Generated with AI, which can make mistakes.

#ai-tools#product-launch
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