QuillBot vs Grammarly AI Humanizer: Which Sounds More Human?

QuillBot and Grammarly both sell an AI humanizer now, but each company built it on top of a different main product. QuillBot suits writers who want sentences rewritten, while Grammarly suits writers who want grammar and tone polished in the same editor.

Neither company promises that its humanizer will change an AI detector’s verdict, and Grammarly says so outright in its FAQ. QuillBot’s free humanizer also stops at 100 words per run, which runs out fast on a full essay.

We checked both tools’ live pricing and help pages in October 2026 for this QuillBot vs Grammarly AI Humanizer comparison. The sections below compare their prices and the detector tests published so far.

Make Your AI-Assisted Draft Read Naturally 👇

What QuillBot and Grammarly Actually Do

QuillBot is a paraphrasing tool built around sentence structure rewriting, and Grammarly is a grammar checker built around grammar, style, and tone correction. Both companies added an AI humanizer later, so a person polishing a work email and a person reworking an AI-generated draft need different tools.

QuillBot: Paraphrasing and Sentence Rewriting

QuillBot's core tool, the Paraphraser, rewords sentences while keeping their meaning. Free accounts get the Standard and Fluency modes, and Premium adds 9 built-in modes, such as Academic and Simple, that change word choice and sentence structure in different ways.

• 🤖 AI Humanizer: QuillBot offers it as a separate tool, with a free Basic mode and a deeper Advanced mode on Premium.

• 🔍 Other tools: a grammar checker and an AI detector come with the free account, and Premium adds a plagiarism checker.

Grammarly: Grammar, Style, and Tone Checking

Grammarly markets itself as a writing assistant that fixes grammar and punctuation and adjusts tone and clarity while you write. Its AI humanizer is a newer feature inside that same product.

• ✅ Grammar checks: Grammarly corrects errors as you type through its browser extension and desktop apps.

• 🎙️ Humanizer agent: a free account adds preset voices and a custom voice built from a writing sample of 200 words or more.

• 🌍 Languages: the humanizer works in six languages, including English and Spanish.

QuillBot vs Grammarly Pricing: Side-by-Side

QuillBot Premium costs $8.33 a month billed annually ($99.95 a year), while Grammarly Pro costs $12 a month billed annually ($144 a year). Grammarly's $12 figure is an annual average, because paying month to month costs $30.

The Grammarly Pro AI Humanizer comes inside the full Pro subscription plan, which Grammarly says adds the complete Humanizer experience along with its advanced writing features. QuillBot Premium, by contrast, lists full humanizer access with no word limit.

Prices are in USD from QuillBot's upgrade page and Grammarly's support page, checked in October 2026. Vendors can change prices for promotional offers or plan updates, so confirm the current price on each vendor's site before you buy.

Both tools also have a free tier, so you can test either humanizer before you pay for a subscription plan.

QuillBot's Free AI Humanizer: Inside the 100-Word Cap

QuillBot's AI humanizer is free to try, but the free plan humanizes up to 100 words per run, with limited usage. The QuillBot AI humanizer word limit goes away on Premium, which QuillBot's humanizer page describes as having no word limit.

QuillBot's own pages give two figures in October 2026. The humanizer page still shows a 125-word limit for the free plan, while the Premium plan comparison lists 100 words.

What Happens After 100 Words

A free run takes no more than the limit, so a 600-word essay needs at least six separate runs. QuillBot also caps how often free accounts can humanize, and you have to check that the tone still matches once you join the pieces back together.

Upgrading for More Humanizer Credits

QuillBot Premium gives full access to humanizing, and its usage limits policy still applies to very heavy use. Premium also adds these humanizer features:

• 🚀 Advanced mode for deeper rewrites and more fluent text

• 🎯 Tone insights that show how your text sounds to readers

• 🕘 Humanize history for quick access to earlier rewrites

Writers who need a whole draft processed in one run can compare QuillBot alternatives built for humanization before they commit to a yearly plan.

Grammarly AI Humanizer Review: How Does It Score on AI Detectors?

Grammarly's humanizer lowers AI detection scores only part of the way in published tests, and Grammarly says the tool isn't designed for that job. Grammarly's AI Detector guide adds that Humanizer rewrites come from Grammarly's own AI model, so its own detector will likely flag them.

What Grammarly Says About Its Own Humanizer

Grammarly answers the detector question in its humanizer FAQ: "This tool is not intended to bypass AI detectors." That FAQ says the humanizer aims to make writing clearer and more coherent. The page headline still promises writing that sounds like you rather than AI, so go by the FAQ if detectors are your concern.

QuillBot makes no detector promise either. Its AI Humanizer page tells users to treat the Human score as a signal rather than a verdict and to follow their institution’s AI guidelines.

Cited Detector Test Results (GPTZero, Originality.ai, ZeroGPT)

Grammarly does detect AI writing through its free AI Detector, which returns a percentage score and claims 99% accuracy on the RAID benchmark. In a November 2024 PCWorld test, that detector scored a fully Gemini-written story at 37% AI on both runs, while Originality.ai scored the same story 100% AI.

The closest thing to a QuillBot vs Grammarly AI Humanizer detector comparison comes from four published results, where QuillBot's Fluency mode scored lowest on GPTZero:

ChimpWrite sells its own humanizer and published these numbers as its own test results. Each row covers one test, so read it as a single reading rather than a success rate.

Why Do Detector Scores Vary So Much?

Detectors weigh different signals, so the same text can score very differently from one tool to the next. GPTZero's help center describes two classic ones: perplexity, meaning how predictable each word choice is, and burstiness, meaning how much that predictability changes. GPTZero adds that a deep-learning model replaced them as the main basis for its score in fall 2023. Turnitin's FAQ says its own model isn't programmed to measure either signal directly and learns patterns from academic writing instead.

Because results shift by detector, we tested five leading AI humanizers head to head before ranking them.

QuillBot vs Grammarly for Turnitin and Academic Integrity

Neither QuillBot nor Grammarly says its humanizer will get text past Turnitin, the AI and plagiarism detector many schools use. Turnitin's guide lists two features aimed at rewritten text: AI paraphrasing detection and AI bypasser detection, which Turnitin added in August 2025 for text changed by humanizer tools.

Does Turnitin Catch QuillBot or Grammarly Text?

Turnitin's FAQ says ordinary Grammarly grammar and spelling fixes are usually not flagged, but content from Grammarly's generative AI features, such as paraphrasing, will likely be flagged. Turnitin won't name the paraphraser or humanizer tools it detects, so no public source confirms how it scores QuillBot's output. Our guide to Turnitin's AI detector explains how Turnitin reviews submitted text.

What This Means for Student Writers

For students, the QuillBot vs Grammarly question matters less than your school's AI policy, so check that policy before you run graded work through any rewriting tool. Grammarly's own FAQ warns that using a humanizer to disguise AI use, where AI is restricted or must be disclosed, may count as cheating or plagiarism.

QuillBot's academic integrity note adds that rewording someone else's idea doesn't make it yours, so cite the source even when a plagiarism detector shows a low match.

What Does Reddit Say About QuillBot vs Grammarly?

Reddit users tend to describe QuillBot as the tool that rewrites and Grammarly as the tool that polishes, but they disagree on which one sounds more natural. Four threads show the split:

• 🔄 Rewriting vs polishing: In r/humanizeAIwriting, one user said QuillBot does more to change sentence structure, while Grammarly mostly fixes grammar and can make text sound more formal. Other commenters in that thread called both tools poor and complained about their word limits.

• 🗣️ Tone: A student in r/writers who compared the paid plans for college essays found the opposite: Grammarly kept their original tone, while QuillBot felt too formal.

• 🚩 AI flags: In another r/writers thread, a writer said Grammarly's AI check flagged their QuillBot-paraphrased paragraph but not the paragraph they wrote themselves.

• 💳 Billing: In r/Grammarly, a user who missed the end of a free trial in October 2026 was charged $144 for the annual plan, then got a refund after opening a support ticket.

A Cybernews review of Reddit discussions found the same pattern: users praise Grammarly's grammar checks, and QuillBot's paraphrasing and lower price. In Cybernews' own plagiarism test on the same copied text, QuillBot flagged about 45.7% and Grammarly roughly 41%, and both tools marked the same sections.

Can You Use QuillBot and Grammarly Together?

You can use QuillBot and Grammarly on the same document, because each tool works through its own browser extension and editor. A common order is a Grammarly pass for grammar and clarity first, then a QuillBot pass for rewording, which free users must split into 100-word runs.

A Combined Workflow Example

1. Write your draft, or generate a first version with an AI content generator.

2. Run the Grammarly browser extension for grammar and clarity edits.

3. Paste the cleaned text into QuillBot's rewriting engine to reword sentences that still sound stiff.

4. Read the result yourself, and fix tone, flow, and any grammar the rewrite changed.

Why Stacking Them Doesn't Change Much on AI Detectors

Neither vendor claims that using both tools changes how detectors score text, and ChimpWrite’s June 2026 test tested QuillBot Fluency and Grammarly rewrites separately. As a result, no published result shows what the two tools do to a detector score together, and each extra pass adds another rewrite you have to check for changed meaning.

Best AI Humanizer 2026: Where Phrasly Fits In

Pay for QuillBot Premium if you mainly need long drafts reworded, and Grammarly Pro if you also want full grammar and tone editing. For humanizing alone, a dedicated humanizer fits the job more closely, because neither QuillBot nor Grammarly built its humanizer as the main product.

In ChimpWrite's own test set, the dedicated humanizer it tested also moved GPTZero scores further than either Grammarly or QuillBot.

Where QuillBot and Grammarly Fall Short

What Phrasly's AI Humanizer Does Differently

Phrasly's AI Humanizer is built for one job: refining AI-assisted drafts into natural-sounding text through tone adjustment and varied sentence structure. Read each output against your original to confirm the meaning stayed the same.

• 📝 Try it first: one run a day of 15 to 500 words, with no signup

• 📏 Unlimited plan: up to 5,000 words per run, for $20 a month or $131.88 a year

• 🎛️ Phrasly Ultra: five rewrite strengths from Gentle to Max on paid plans and the trial, plus settings for commas, sentence length, and cleaner grammar

Phrasly's prices were checked in October 2026 and can change with promotional offers or plan updates.

Students should also read our AI humanizer guidance for academic writing, which covers how to keep citations and meaning intact during a rewrite.

Frequently Asked Questions