Comparing English Writing Assistants: Grammarly vs LanguageTool vs Local Tone

The market for English writing assistance has expanded significantly since LLMs became widely accessible. For a professional evaluating writing tools, the choices split roughly into three categories: traditional rule-based grammar checkers with surface-level suggestions, AI-powered style tools that rewrite entire passages, and specialised tools designed for specific writing contexts or user profiles.

This article compares three tools that represent different philosophies: Grammarly (the established market leader), LanguageTool (the open-source alternative), and Local Tone (the option focused on first-language transfer and regional calibration). The comparison is from the perspective of a professional writing in their second language — someone who is functionally fluent in English but whose writing is shaped by their native language in specific ways.

I built Local Tone, so I am not a neutral party here. I will be explicit about what each tool does well and where it falls short.

Grammarly

What it does: Grammarly is a browser-integrated grammar and style checker. The free tier catches grammatical errors, spelling mistakes, and punctuation issues. The premium tier adds style suggestions: passive voice, wordiness, tone detection, and clarity scores. The Business tier adds team features.

Strengths:

Very wide integration. Works in Gmail, Google Docs, Slack, Microsoft Office, and most browser text fields.
Real-time suggestions. You see corrections as you type.
Good at surface errors: subject-verb agreement, comma splices, run-on sentences.
Tone detection gives a rough indication of whether your email reads as confident, formal, or friendly.

Weaknesses for non-native professional writers:

Grammarly treats English as a single standard variety. It does not distinguish between Australian, British, Canadian, and American English conventions in tone or vocabulary — only in spelling.
It does not understand first-language transfer patterns. If you consistently write "please kindly" or use "I think" for facts (Cantonese/Korean transfer), Grammarly does not flag these.
The "clarity" suggestions are based on surface heuristics (sentence length, word frequency) rather than comprehension of meaning. They often propose rewrites that are shorter but less precise.
The passive voice flag is applied indiscriminately, flagging legitimate deliberate uses alongside genuinely problematic ones.
Premium pricing ($30/month for full features) is relatively high for what is essentially a style checker.

Best for: Writers who need broad surface-level polish and wide integration. Not specialised for first-language transfer issues or regional calibration.

LanguageTool

What it does: LanguageTool is an open-source grammar checker with support for 30+ languages. It works as a browser extension, desktop app, and API. A self-hosted option is available.

Strengths:

Open-source core. You can self-host the grammar checking engine if privacy is a concern.
Supports many languages, which is useful if you write in your first language as well as English.
Free tier is more generous than Grammarly's.
Good rule-based grammar checking for basic errors.

Weaknesses for non-native professional writers:

Similar to Grammarly, LanguageTool applies a single-variety standard for English. Regional calibration is limited to spelling.
The AI-powered suggestions in the premium tier are less well-developed than Grammarly's in terms of tone and style.
First-language transfer patterns are not a design consideration.

Best for: Writers who want a privacy-conscious, open-source option for grammar checking. The self-hosted deployment is a genuine advantage for organisations with strict data policies.

Local Tone

What it does: Local Tone is an LLM-powered writing tool designed for professionals writing in their second language. It analyses your draft for first-language transfer patterns, rewrites for your chosen region (AU / CA / IE / UK / US / Global) and tone mode (professional or daily life), explains each change, and tracks your recurring patterns over time.

Strengths:

Regional calibration is a core feature, not an afterthought. The AU, UK, US, and other presets apply different vocabulary, hedging norms, and sign-off conventions.
First-language transfer detection. If you write with Cantonese, Mandarin, Korean, Japanese, German, or French transfer patterns, the tool identifies the specific habit and explains the impact on an English reader.
Pattern tracking. The dashboard shows your recurring habits across sessions, so you can watch them improve rather than correcting the same thing indefinitely.
BYOK tier keeps the effective cost of AI analysis under a cent per use.
Explains changes rather than just making them. The notes help you learn, not just copy.

Weaknesses:

No real-time as-you-type suggestions. You paste a completed draft for analysis, rather than getting inline corrections.
No browser integration (no Gmail or Google Docs plugin).
Not designed for grammar checking — it does not catch spelling errors or comma splices.
Smaller tool with less market presence than Grammarly. Fewer integrations.

Best for: Professionals who write regularly in English and want to understand and reduce their specific first-language habits, with calibration for a specific English-speaking region.

The Practical Recommendation

For most non-native professional writers, the answer is to use more than one tool:

Grammarly or LanguageTool for real-time grammar and spelling checking integrated into your usual writing environment.
Local Tone for analysis of important drafts (client emails, proposals, performance reviews) where regional calibration and first-language-aware rewriting matters.

The two categories are not substitutes. A grammar checker handles surface correctness. Local Tone handles deeper phrasing and regional calibration.

If you are writing for an Australian or UK audience and find that your writing is consistently being rephrased by native-speaker colleagues, grammar checking alone is not addressing the root cause. The issue is first-language transfer and regional miscalibration, which is what Local Tone is designed for.

If you write casually and your main concern is typos and punctuation, Grammarly's free tier or LanguageTool is sufficient.

How to Choose Based on Your Situation

You are a senior professional writing in Australian or UK English with a Cantonese, Mandarin, Korean, or Japanese background: Local Tone. The regional calibration and first-language detection are the primary value.

You primarily need grammar and spelling checking in real-time: Grammarly or LanguageTool.

You work at a company with strict data policies and want self-hosted grammar checking: LanguageTool self-hosted.

You write for multiple English-speaking regions and want the output calibrated for each: Local Tone.