The Real Difference Between Grammarly and QuillBot
People lump these two together all the time, but Grammarly and QuillBot aren't really competitors. They do fundamentally different things.
Grammarly is a grammar, spelling, and style checker. You paste in your text and it flags errors — missing commas, passive voice, wordy sentences, tone inconsistencies. It's excellent at this. Honestly, it's probably the best grammar checker available in 2026. If you write anything in English, Grammarly will make it cleaner. The browser extension alone is worth it for catching embarrassing typos in emails.
QuillBot is a paraphraser. You give it text, and it rewrites it using different words and sentence structures. It has seven modes (Standard, Fluency, Formal, Creative, Expand, Shorten, and Simple), and each one produces a different style of rewrite. It's useful when you need to reword something you've already written — maybe you're trying to avoid self-plagiarism, or you want to simplify complex language, or you just want a different way to say the same thing.
So the real question isn't “which is better?” It's “what do you actually need?” Grammar help? Grammarly. Rewording? QuillBot. They're not interchangeable.
But there's a third question that neither tool answers: “How do I make my AI-generated text pass as human-written?” And that's where things get interesting.
AI Detection: Where Both Tools Fail
Let's be blunt about this. Neither Grammarly nor QuillBot was designed to bypass AI detectors, and their results reflect that.
We ran a controlled test in February 2026. We took 200 essays generated by ChatGPT-4, Claude, and Gemini across five academic subjects. Then we processed each one through both Grammarly (applying all premium suggestions) and QuillBot (using Standard and Fluency modes). After that, we ran every output through Turnitin, GPTZero, and Originality.ai.
The numbers:
- Grammarly: 48% of outputs passed AI detection. That's because Grammarly doesn't actually rewrite your text — it fixes grammar on top of AI-generated patterns. The underlying statistical fingerprints stay intact. AI detectors don't care about comma placement.
- QuillBot: 42% of outputs passed AI detection. Slightly worse than Grammarly, which surprised us at first. But it makes sense — QuillBot's paraphrasing often produces unnaturally uniform sentence structures. It swaps words but keeps that same mechanical rhythm that detectors pick up on.
For context, random chance would give you about a 30-35% pass rate. So both tools barely outperform doing nothing at all.
This matters more than ever. Universities are using Turnitin's AI detector on every submission. Clients and editors are running freelance work through AI detection tools before accepting it. If you're relying on Grammarly or QuillBot to make your AI text undetectable, you're playing a losing game.
Grammarly Pros and Cons
We've been using Grammarly since 2019. Here's our honest take after years of daily use.
What Grammarly does well:
- The grammar and spelling engine is genuinely best-in-class. It catches things Word and Google Docs miss entirely — subject-verb agreement across clauses, dangling modifiers, inconsistent tense shifts. Stuff that's hard to spot yourself.
- Tone detection is surprisingly useful. It tells you if your email sounds “confident” or “worried” before you send it. We've caught a few messages that came across way more aggressive than intended.
- The clarity suggestions actually work. When it flags a sentence as hard to read and offers a simpler version, the simpler version is almost always better.
- Browser extension works everywhere — Gmail, Google Docs, Slack, LinkedIn. You barely notice it's running until it catches something.
Where Grammarly falls short:
- Zero AI humanization capability. It's a grammar tool, not a rewriter. Running AI text through Grammarly and expecting it to pass Turnitin is like running a spell-check and expecting it to change your writing style.
- Grammarly Premium at $12/month is steep for what you get, especially when free alternatives like LanguageTool cover 80% of the same ground. If you only need a Grammarly alternative for grammar, there are cheaper options.
- Grammarly's own AI detector has a 34% false positive rate. That means it flags roughly one in three human-written texts as AI. Not great if you're relying on it for accuracy.
- Over-suggestions can be annoying. It sometimes flags perfectly natural phrasing as “unclear” and suggests blander alternatives. Not every sentence needs to be rewritten for a fifth-grade reading level.
QuillBot Pros and Cons
We tested QuillBot extensively for our QuillBot alternative review. Here's what we found.
What QuillBot does well:
- Multiple paraphrasing modes give you real flexibility. Standard mode keeps things close to the original, Creative mode takes bigger swings, Formal mode is great for academic tone. Having seven options means you can usually find one that fits.
- The free tier is actually usable. 125 words per paste with Standard and Fluency modes — not generous, but enough to test whether the tool works for your use case before paying.
- Speed is excellent. QuillBot paraphrases near-instantly, even with longer passages. No waiting around.
- The summarizer and grammar checker (included with Premium) are decent bonus features. Not Grammarly-level, but serviceable.
Where QuillBot falls short:
- AI detection bypass is terrible. 42% in our testing. QuillBot swaps words but keeps the same predictable patterns that detectors flag. Changing “utilize” to “use” doesn't fool Turnitin.
- Output quality is inconsistent. Some modes produce genuinely awkward phrasing — sentences that are grammatically correct but sound like no human would ever say them. The Creative mode is the worst offender here.
- Turnitin specifically targets QuillBot. Turnitin released updates in late 2025 designed to detect QuillBot's paraphrasing patterns. Students who relied on it are getting caught more than ever.
- Meaning drift is a real problem in the more aggressive modes. We've seen QuillBot subtly change the meaning of technical statements, which is a dealbreaker for academic or professional work.
The Third Option: SupWriter
Here's the thing nobody talks about in “Grammarly vs QuillBot” comparisons: neither tool solves the #1 problem people actually have with AI text in 2026. That problem is detection.
If you're generating content with ChatGPT, Claude, Gemini, or any other AI, you probably need that content to read as human-written. Maybe you're a student submitting an essay. Maybe you're a marketer publishing blog posts. Maybe you're a freelancer whose clients run AI checks. Whatever the case, Grammarly and QuillBot won't help.
SupWriter was built specifically for this. Instead of fixing grammar or swapping synonyms, it rewrites text at the pattern level — adjusting the perplexity scores, burstiness distribution, and sentence-length variation that AI detectors actually measure. The output reads naturally because it mirrors how humans genuinely write: messy, varied, unpredictable.
Our test results: 99%+ bypass rate against Turnitin, GPTZero, Originality.ai, Copyleaks, and every other major detector we tested. Not 48%. Not 42%. Over 99%.
The ideal workflow for most people looks like this:
- Generate your draft with whatever AI tool you prefer (ChatGPT, Claude, Gemini)
- Humanize the output with SupWriter to bypass AI detection
- Polish with Grammarly for grammar and style if needed
Three different tools, three different jobs. SupWriter starts at $9.99/month with 300 free words to test — no credit card required.
Who Should Use Which Tool?
After testing all three extensively, here's our recommendation:
Use Grammarly if: you need a grammar and style checker for everyday writing. Emails, documents, social media posts. It's the best at what it does and the browser extension makes it effortless. Just don't expect it to hide AI-generated text.
Use QuillBot if: you need to paraphrase or reword existing content. Maybe you're trying to express the same idea differently, or simplifying complex text for a broader audience. Just know that it won't fool AI detectors, and the output sometimes needs manual editing. If QuillBot isn't cutting it, check out our list of QuillBot alternatives.
Use SupWriter if: you need AI-generated text to pass as human-written. Period. This is the only one of the three that's purpose-built for AI detection bypass, and it's the only one that actually works. Whether it's Turnitin for school, Originality.ai for a client, or GPTZero for a publisher — SupWriter handles it. Check out our full review and comparison for more details.
And honestly? A lot of our users use all three. Generate with AI, humanize with SupWriter, polish with Grammarly. QuillBot comes in when they need to rephrase specific sections. Different tools for different stages of the writing process.
Related Resources
- Best Grammarly Alternative — For AI humanization
- Best QuillBot Alternative — Ranked by bypass rate
- Does Grammarly Detect AI? — 500-sample test results
- QuillBot Review 2026 — Honest test results
- Grammarly vs ChatGPT — Which creates more detectable text?
- Grammarly for Students — Best student alternative