AmberPen Get started Practical engineering guides on proofreading, language APIs, and the details that make writing software feel effortless.
Sapling is one of the few writing assistants with a real grammar API. An honest look at its Edits API, pricing, benchmark results, and alternatives.
Read articleLanguageTool's API is free and self-hostable, but production use hides real costs. An honest guide to the public endpoint, self-hosting, and managed options.
Read articleProWritingAid has no public grammar-correction API. Here's what its developer options actually cover — and the proofreading APIs that return real corrections.
Read articleQuillBot and Grammarly solve different problems. An honest comparison of their grammar checking, paraphrasing, pricing, and where each one falls short.
Read articleLanguageTool is cheaper, multilingual, and open source; Grammarly is smoother and English-only. An honest comparison of quality, price, and privacy.
Read articleGrammarly's price keeps climbing. Nine alternatives tested — free, cheaper, private, and open-source picks — ranked by what you actually write.
Read articleGrammarly and ProWritingAid solve different problems. An honest comparison of correction quality, pricing, integrations, and who each tool is really for.
Read articleMicrosoft retired the Bing Spell Check API in August 2025. Compare working alternatives and migrate a Bing client to a proofreading API in fifteen lines.
Read articleAdd real-time grammar checking to a TipTap or ProseMirror editor — map edit offsets to positions, render suggestion decorations, and apply corrections.
Read articleCompare the leading grammar checker APIs on correction quality, latency, edit format, privacy, and price — with benchmark data on public English corpora.
Read articleLearn how to add fast, contextual grammar correction to an editor with a proofreading API, stable text edits, streaming, and custom terms.
Read articleManifest V3, content scripts, and the CSS Custom Highlight API — build a Chrome extension that underlines grammar issues with a proofreading API.
Read articlePrompting ChatGPT or another LLM to fix grammar works in a demo. In production it breaks in five specific ways — and there's a cleaner architecture.
Read articleBuild a CodeMirror 6 grammar-check extension — a mapped decoration field that survives typing, hover tooltips, and skipping code blocks in Markdown.
Read articlePer-character, per-token, per-seat, or self-hosted — the four proofreading billing models, the multipliers that inflate them, and cost math for three products.
Read articleGLEU vs ERRANT F0.5, JFLEG vs CWEB — what grammar-correction benchmarks actually measure, and how to read any vendor's numbers skeptically.
Read articleCorrections alone don't teach writing. How to build grammar feedback that explains itself — per-edit reasoning, categories, restraint, and student privacy.
Read articleGrammarly has developer APIs, but none return grammar corrections. Here's what Grammarly's APIs actually do — and the proofreading APIs to use instead.
Read articleWire a proofreading API into a Lexical editor — map API offsets to Lexical points, render suggestions as MarkNodes, and apply fixes as ordinary undoable edits.
Read articleRe-proofreading an entire document on every pause wastes money and adds latency. Incremental proofreading checks only what changed — here's how it works.
Read articleLanguageTool and Harper make self-hosted grammar checking tempting. Here's the honest math on quality ceilings, ops burden, and when a managed API wins.
Read articleToken streaming gives you unusable partial JSON. Streaming complete, validated edit batches gives users suggestions in milliseconds. Here's the design.
Read articleStart with a free test key and add production-grade proofreading to your app in minutes.