Short answer
For everyday emails and documents, a grammar checker is the most useful single tool. For first drafts, use a general AI assistant such as ChatGPT or Claude, then run the result through a checker and read it yourself. Pick the tool by the job, check its privacy settings before pasting anything confidential, and always verify facts, names and numbers by hand.
AI writing tool guides, by kind
Which checker catches the most errors with the fewest false alarms, tested on real emails and reports. Covers Grammarly, Hemingway and AI proofreaders, free and paid.
Drafting assistants for business and marketing copy, reviewed on output quality, tone control and price. Includes Jasper, Copy.ai and prompts for ChatGPT.
Head-to-head tests on the same set of texts, so you can see exactly where two tools differ.
Ranked picks for each use, from all-round writing assistants to AI email writers.
The best no-cost checkers and aids, including tools that suit writers whose first language is not English.
Which tool suits the job
Start from what you write, not from the brand. Each row links to the review that tests that case. The guides by kind of tool are listed above.
| You write | Kind of tool | Why | Read |
|---|---|---|---|
| Business emails and reports | Grammar checker | Catches errors as you type, inside email and documents. | Best grammar checker |
| Proposals and client documents | AI writer + checker | Draft faster, then check tone and accuracy. | Best AI for business writing |
| Novels and long-form writing | Style report tool | Whole-document reports on pacing, repetition and sentence length. | Grammarly vs ProWritingAid |
| Plain, readable copy | Readability editor | Highlights long sentences, passive voice and adverbs. | Hemingway Editor review |
| English as a second language | Multilingual checker | Explains corrections and supports more than one language. | Tools for non-native speakers |
| On a zero budget | Free checker | Running two free tools catches more than either alone. | Top free grammar tools |
Five kinds of tool compared
“AI writing tool” covers very different products. Knowing which kind you need saves paying for features you will not use.
| Kind | What it does | Best for | Check yourself | Examples |
|---|---|---|---|---|
| Grammar checker | Underlines spelling, grammar and punctuation errors as you type and suggests fixes. | Emails, reports, anything that must be correct | Suggestions that change your meaning; confident but wrong fixes on names and technical terms | Grammarly, LanguageToolBest grammar checker 2026: free and paid → |
| Style editor | Produces reports on sentence length, repetition, passive voice and readability. | Long documents and fiction | Over-simplifying: not every long sentence is a bad one | ProWritingAid, Hemingway EditorHemingway Editor Review: Simple and Powerful → |
| General AI assistant | Writes, rewrites, summarises and explains from your instructions. | First drafts, outlines, rewording | Invented facts, quotes and sources; a generic tone | ChatGPT, Claude, GeminiChatGPT vs Claude for Writing → |
| Marketing AI writer | Templates for ads, product descriptions and social posts, often with brand-voice settings. | High volumes of short copy | Repetitive phrasing across many pieces | Jasper, Copy.aiJasper AI Review 2026: Pros, Cons and Pricing → |
| Paraphraser | Rewords a sentence or paragraph in several modes (simpler, formal, shorter). | Finding another way to say one sentence | Meaning drift; using it to disguise copied work is plagiarism | QuillBotGrammarly vs QuillBot: Which Is Better? → |
One email, four passes
The best results come from using tools in sequence, each for what it does well. Here is a short client email taken through four passes, with a note on what each pass changed. For pass 1, ChatGPT prompts for professional writing and our prompt guide show how to ask for a usable draft.
1 · AI draft Hi Maria, I wanted to reach out regarding the project timeline, which has been impacted by some unforeseen delays that were experienced by our team. Fluent and fast, but wordy, with a passive “were experienced” that hides who did what.
2 · Grammar check Hi Maria, I’m writing about the project timeline, which unforeseen delays in our team have affected. The checker shortened “reach out regarding” and turned the passive into an active verb.
3 · Your edit Hi Maria, the launch will move from 3 June to 10 June. Our designer was ill for a week, and I’d rather delay than rush. You add the real news first, the reason, and your own voice. No tool knew any of this.
4 · Fact check Hi Maria, the launch will move from 3 June to 17 June… Checking the plan showed the new date is 17 June, not 10. One wrong number undoes a good email.
Free or paid: what the upgrade buys
Most tools are “freemium”: a free version with limits and a paid plan that removes them. The free tier is usually enough for correct spelling and grammar. Pay when you need the features in the right-hand column every week. We test the difference in detail in Grammarly Premium vs Free and the best free grammar tools.
Usually free
✓Spelling and basic grammar corrections✓Punctuation fixes✓A limited number of AI rewrites per day✓Browser extension for email and web forms✓Basic readability score
Usually paid
+Rewriting whole sentences for clarity and tone+Full style reports for long documents+Plagiarism checks against published text+Team style guides and brand voice+Higher limits on AI generation and longer inputs
Privacy before you paste
Anything you paste into an online tool is sent to the company’s servers. Before you paste a contract, a medical note or anything about a client, check these five things in the tool’s settings and privacy policy.
- Is my text used for training?Look for a setting that stops the company using your text to train its AI, and turn it off for work material.
- How long is it kept?Some tools delete text after a session; others keep a history. Prefer short retention.
- Where is it processed?For EU or UK client data, check the tool offers EU processing or a data protection agreement.
- Is there a business plan?Business and enterprise plans usually add stronger privacy terms. Use them for company documents.
- Can I remove the details?Replace names, account numbers and addresses with placeholders before pasting; add them back afterwards.
How to choose a tool in five steps
| Step | What to do | How |
|---|---|---|
| 1 | Name your main job | Correcting, drafting, rewording or long-document editing. The table at the top of this page matches each to a kind of tool. |
| 2 | Check where you write | Make sure it works inside your email, browser, Word or Google Docs. |
| 3 | Run your own test | Paste in three real pieces of your writing, one with a known error, and see what it catches and what it wrongly flags. |
| 4 | Start on the free tier | Use it for two weeks. Upgrade only if you keep hitting a limit you care about. |
| 5 | Keep a second opinion | Running two free checkers catches more than either alone; your own final read catches the rest. |
Head to head
Grammarly VS ProWritingAid Fast inline fixes in every app.Deep reports for long documents. Read the comparison → ChatGPT VS Claude Tested on drafting and rewriting.Tested on tone, accuracy and long texts. Read the comparison → Grammarly VS QuillBot Corrects grammar and clarity.Paraphrases and rewords. Read the comparison → Grammarly VS Hemingway · PWA Four checkers on one test set.Accuracy, false alarms, privacy. Read the four-way test →
Writing in another language? A checker can fix a sentence, but it can't teach you the language. LangLibra courses in Russian, Spanish, German and French take you all the way to fluent reading, writing, speaking and listening.
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