SMF·HEMINGWAY-EDITOR-PLUS
Can a prompt replace Hemingway Editor Plus?
AI writing — grammar, editing and long-form writing
Exhibit tracking slip
Verdict
The actual Hemingway feature set — a Flesch-Kincaid-style grade-level score, and rule-based highlighting of long sentences, adverbs, and passive constructions — is entirely deterministic and genuinely a one-sitting build, no model required for the core loop. Adding an optional LLM rewrite button on top is a clean extra, not a dependency; the deterministic scoring is what actually earns the "yes."
Exhibit A — The prompt
Received on31.07.2026Build a local readability editor: deterministic grade-level scoring and highlighting, with an optional LLM rewrite. Stack: a local web app (React + a small Node backend, or fully client-side), no database required — this operates on whatever text is pasted in, session by session.
Core loop: as the user types or pastes text, compute a Flesch-Kincaid grade-level score in real time using a standard, well-documented formula (syllables per word, words per sentence) — entirely client-side, no network call. Highlight, with distinct colors: sentences over roughly 20 words ("hard to read"), adverbs (via a simple suffix/word-list heuristic, not a full NLP model), passive-voice constructions (a regex-based heuristic looking for "was/were + past participle" patterns), and complex words that have simpler common alternatives (matched against a small hand-built substitution list). Clicking a flagged sentence optionally sends just that sentence to an LLM API for a rewrite suggestion, shown as an accept-or-reject diff — this part is opt-in and the app is fully useful without it.
The deterministic scoring needs no API key at all. The optional rewrite feature needs an Anthropic or OpenAI key; without one, that button is simply hidden or disabled, and the core scoring and highlighting work exactly the same.
Do not build: cross-device sync, browser or Google Docs extensions, or team style-guide sharing — this is a single-document local editor. Do not let the passive-voice or adverb heuristics silently over-flag; document their known false-positive patterns in the README rather than pretending the regex is a full grammar model.Opening prefills the prompt — press enter to run it.
Exhibit B — What you lose
- B.1 years of tuning on exactly which sentence patterns actually read as awkward, not just technically long
- B.2 cross-device sync of documents and settings
- B.3 browser and word-processor extensions
- B.4 team style guides shared across an organization
- B.5 polish on the AI rewrite feature specifically, versus a generic prompt
Prior art
Exhibit C — Why people still pay: polish, integrations, and proprietary language models
People pay for Hemingway because a deterministic readability score is easy to compute but hard to tune — flagging genuinely awkward sentences without also flagging every technically-long-but-clear one takes real editorial calibration across a lot of real writing, which is exactly the kind of tuning a first-pass local build won't have out of the box.
Questions
Can I import my existing Hemingway documents?
Hemingway doesn't store documents server-side by default — most users' text lives wherever they wrote it originally, so there's nothing to migrate beyond copy-pasting into the new editor.
Will it work on my phone?
As a responsive web page, the scoring and highlighting work on mobile, though editing longer text comfortably is still better suited to a keyboard.
What does it cost to run?
Nothing for the core scoring and highlighting — it's pure local computation. The optional LLM rewrite costs a fraction of a cent per sentence sent, only when you click it.
What's the one thing that doesn't survive the rebuild?
Calibration. Hemingway's rules were tuned over years against real writing to catch genuinely awkward sentences without flooding the page with false positives; a first-pass regex heuristic here will both miss real problems and over-flag clear, simply long sentences until you spend real time tuning it against your own writing.
Related tools
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