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Originality.ai is our best fit for most buyers: it combines AI detection with plagiarism and fact checks, and supports bulk scans. GPTZero, Winston AI and Pangram are stronger picks for specific workflows, including education, mixed-format reviews and image checks. But an AI score is a clue, not proof of authorship. We rank detection usefulness ahead of general writing features, so tools such as Grammarly and Sapling land lower despite their broader appeal. Listed prices start at $8.33, and some tools offer free plans.
Quick picksThe shortlist
Originality.aiOriginality.aiBest overall · $12.95/mo
GPTZeroGPTZeroBest for educators · $12.99/mo
PangramPangramBest for image checks · $20/mo
Winston AIWinston AIBest for mixed formats · $10/mo
CopyleaksCopyleaksBest for schools · $13.99/mo
SaplingSaplingBest for workspaces · $12/mo
QuillBotQuillBotBest for paraphrasing · $8.33/mo
GrammarlyGrammarlyBest for proofreading · €12/mo
QuetextQuetextBest for bundled checks · $14.99/mo
iThenticateiThenticateBest for researchers · $125/mo
SmodinSmodinBest for tool bundles · $10/mo
DupliCheckerDupliCheckerBest for quick checks · $9.17/mo
ZeroGPTZeroGPTBest free starting point · Free
01Compared at a glance
| Tool | Score | From | Free plan | Trial |
|---|---|---|---|---|
| Originality.aiOriginality.ai | 5.8 | $12.95/mo | Yes | — |
| GPTZeroGPTZero | 5.8 | $12.99/mo | Yes | — |
| PangramPangram | 6.2 | $20/mo | No | 7 days |
| Winston AIWinston AI | 5.4 | $10/mo | Yes | 14 days |
| CopyleaksCopyleaks | 5.4 | $13.99/mo | No | — |
| SaplingSapling | 7.0 | $12/mo | Yes | 1 month |
| QuillBotQuillBot | 6.0 | $8.33/mo | Yes | — |
| GrammarlyGrammarly | 6.5 | €12/mo | Yes | 2 days |
| QuetextQuetext | 6.4 | $14.99/mo | Yes | — |
| iThenticateiThenticate | 6.4 | $125/mo | No | — |
| SmodinSmodin | 5.9 | $10/mo | No | — |
| DupliCheckerDupliChecker | 5.7 | $9.17/mo | Yes | — |
| ZeroGPTZeroGPT | 5.4 | Free | Yes | — |
02The picks, in detail
- Best overallOriginality.aiOriginality.ai
Originality.ai offers AI detection alongside plagiarism and fact checks, with bulk text scans for teams. That mix makes it our strongest all-around pick for writers and publishers checking drafts. The listed starting price is $12.95, with a free plan. Its own published guidance is the right caution: treat detection as a clue, not a verdict.
What works
- Free plan includes access to several writing checkers
- Pro includes 200,000 words per month
- Deep Scan explains why text was flagged
What doesn't
- Reddit users report false positives on human writing
- Detector scores should not stand alone as proof
- Free use is limited
- Best for educatorsGPTZeroGPTZero
GPTZero is a good fit for educators who need LMS integrations, while its shared billing and occasional individual scans also suit other users. The listed starting price is $12.99, with a free plan. Its detection features are broad, but the score should be treated as a signal—not proof—so don’t use it alone to make a high-stakes authorship call.
What works
- Checks text from several major AI models
- Includes plagiarism checking and writing feedback
- Writing Replay shows typing and copy-paste events
What doesn't
- Homepage accuracy claim lacks methodology here
- Reddit users report false positives
- Reddit users report conflicting detector results
- Best for image checksPangramPangram
Pangram suits editors reviewing AI-assisted drafts and teams that want shared billing, with text and image checks listed among its strengths. It starts at $20. That makes it a more specialized, higher-priced choice than several options here. Its scores are disputed, so we would not treat a result as reliable proof of who—or what—wrote a piece.
What works
- Checks text and images, with video detection also listed
- Shows AI segments instead of only a yes-or-no result
- Flags AI-assisted edits, not just fully AI-written text
What doesn't
- No free plan; Individual starts at $20/month
- Reddit users report human writing receiving high AI scores
- Some users report results that conflict with other detectors
- Best for mixed formatsWinston AIWinston AI
Winston AI is worth considering if your review process involves mixed-format submissions or you want AI detection and plagiarism checks together. It also suits teams comparing detector results. The listed starting price is $10, with a free plan. Its score still isn’t proof of authorship; use it as one input, not a final decision.
What works
- Bundles text, image and deepfake detection
- Includes OCR for documents, pictures and handwriting
- Sentence-level AI prediction map
What doesn't
- Reddit users report false positives on human-written essays
- The 99.87% accuracy claim is not independently verified here
- Essential limits scans to 200,000 characters
- Best for schoolsCopyleaksCopyleaks
Copyleaks has a wide detection toolkit and is a fit for schools needing LMS integrations, teams scanning websites and organizations building API workflows. Its listed starting price is $13.99. The published buying notes flag score disputes and credit limits, so check the limits against your workload and avoid treating a detector result as conclusive evidence.
What works
- AI detection covers 30+ languages
- Plagiarism checks cover 100+ languages
- Checks text, code, images and video
What doesn't
- No free plan is listed
- Personal includes 100 monthly credits
- Annual billing is paid upfront
- Best for workspacesSaplingSapling
Sapling is strongest for teams adding writing tools to workspaces, developers integrating language features and individuals using snippets or autocomplete. It starts at $12 and has a free plan. Its score is the highest in this shortlist, but detector caps and limited relevant public feedback make it harder to recommend as a detector-first purchase.
What works
- Combines grammar, detection, autocomplete and rephrasing
- Free plan includes basic writing suggestions
- Pro includes unlimited snippets and autocomplete
What doesn't
- Free detector checks cap at 2,000 characters
- Pro costs $25 monthly without annual billing
- API has a one-time $5 minimum charge
- Best for paraphrasingQuillBotQuillBot
QuillBot combines grammar fixes and paraphrasing, with unlimited paraphrase rewrites and centralized per-seat billing listed as reasons to consider it. It starts at $8.33 and has a free plan. That’s a low entry price, but its humanizer is not a safe bet for passing AI detectors. Choose it for rewriting help, not to certify human authorship.
What works
- Free plan covers basic grammar and spelling fixes
- Premium unlocks unlimited paraphrasing across 9+ modes
- Team seats scale down to $5.83/mo at 51+ users
What doesn't
- Free tier limited to 125 words per paraphrase run
- Plagiarism Checker locked out entirely on free plan
- Team plan has no monthly option, annual only
- Best for proofreadingGrammarlyGrammarly
Grammarly is a better fit for proofreading business emails, essays and theses than for buyers focused on AI detection. Teams can also use shared style guides. It starts at $12 and has a free plan. Its free proofreader may be enough for casual writing; the published guidance warns that Pro’s rewrites and prompts may not justify the extra cost for those users.
What works
- Free plan catches real errors without a subscription
- Works inside Zendesk and most browser text boxes
- Pro adds full-sentence rewrites, not just word swaps
What doesn't
- Pro costs roughly $140/year, called debatable value on Reddit
- Multiple Reddit users say it weakens fiction and creative voice
- Comma suggestions criticized as overzealous by some users
- Best for bundled checksQuetextQuetext
Quetext is worth a look if you want several writing checks in one tool, occasional scans within free word caps or bulk uploads. It starts at $14.99 and has a free plan. Compare the paid caps with your expected volume before switching: the published notes identify those limits as a key part of the buying decision.
What works
- Free plan includes plagiarism and AI checks
- Free AI summarizer allows up to 2,000 words
- Paid plans bundle plagiarism and AI checks
What doesn't
- Free plagiarism and AI checks stop at 1,000 words
- Essential's yearly rate is not published
- Additional-word pricing is not published
- Best for researchersiThenticateiThenticate
iThenticate is a specialized similarity tool for researchers checking manuscripts, publishers screening high-stakes documents and institutions seeking custom organization pricing. It starts at $125; individual credits cost $125–$300, and AI detection is excluded. That makes it a poor fit if you specifically need an AI detector, but a relevant option for manuscript similarity screening.
What works
- Single purchase covers up to 25,000 words
- Multiple purchase covers up to three manuscripts
- Five free revisions on individual packages
What doesn't
- Single purchase costs $125
- Multiple purchase costs $300
- Individual packages exclude AI writing detection
- Best for tool bundlesSmodinSmodin
Smodin bundles several writing tools and suits users who need multilingual writing features or are comfortable paying. It starts at $10, and there is no free plan. The published guidance cautions that detector-safe rewriting is not a sure thing. Buy it for the tool bundle if it fits your workflow, not on the promise that rewritten text will evade detection.
What works
- Bundles writing, chat, detection, humanizing and plagiarism checks
- Homepage lists support for over 100 languages
- Premium includes unlimited writing output
What doesn't
- No free plan is listed
- Starter has limited writing output
- Homepage’s 99.8% accuracy claim is unverified
- Best for quick checksDupliCheckerDupliChecker
DupliChecker suits quick plagiarism checks and users who want several tools on one site. It starts at $9.17 and has a free plan. The published notes recommend verifying flagged matches and say evidence for trusting its detection results on their own is weak. That makes it a low-commitment option for checks, not a strong basis for an authorship decision.
What works
- Plagiarism, AI detection, paraphrasing and grammar tools in one site
- Accepts pasted text and seven listed file formats
- Supports up to seven languages
What doesn't
- Free-plan usage limits are not published
- AI-detection accuracy information is not provided
- Reddit users report confusing or mismatched plagiarism flags
- Best free starting pointZeroGPTZeroGPT
ZeroGPT is worth trying if you want free writing tools or need to check short text for AI signals. It has a free plan, but a paid starting price is not published. Its bundled writing tools may be useful, yet the detector score is not proof of authorship. Keep the result as a prompt to review the text, not a verdict.
What works
- Free plan costs $0
- Up to 15,000 characters per detection scan
- Highlights AI-written sentences and shows a percentage
What doesn't
- Personal and Business / EDU prices are not published
- Free plan includes zero batch files
- Free plagiarism checking is limited to 300 words, one time
03How we chose
We compare the 13 listed tools on published pricing, plan limits, documentation and Reddit sentiment, with attention to how each handles false positives and explains its detection claims. We do not treat a vendor’s accuracy claim as an independent result, and we do not claim hands-on testing, benchmarks or screenshots. When a price, limit or policy is not stated in the material available to us, we mark it as not published rather than estimate it. The aim is to help teams compare costs and review requirements before switching.
04Choose a detector for the decision you need to make
An AI detector can help prioritize text for review, but its score should not decide whether a writer used AI. False positives can affect people who write in formulaic, edited or second-language prose, so look for clear explanations of results and a way to contest or review a flag. Before choosing, decide who will read the output, what action a high score triggers and whether the tool fits that process. Editors may need a review queue; SEO teams may care about handling many pages. Compare Grammarly, QuillBot, Originality.ai, GPTZero, Copyleaks, Winston AI, ZeroGPT, Pangram, Sapling, Smodin, DupliChecker, iThenticate and Quetext against those needs. Do not compare vendor accuracy claims as if they came from the same test unless the methodology and sample are comparable.
05Compare total cost, limits and review overhead
A low entry price is not the whole cost. Check what each published plan includes, how usage is measured, and whether the limit fits your typical workload. If a pricing page or documentation does not state a limit, treat it as unknown—not unlimited. Also account for the human time required to investigate flags, explain decisions and handle appeals. Ask whether the tool’s documentation describes what its score means, what text it evaluates and how it treats uncertain results. If those details are missing, that is a buying risk, especially for publishers making consequential decisions. Reddit comments can surface user concerns, but they are anecdotal, not a controlled accuracy test. Shortlist tools only after matching their published terms and documented workflow to your needs; verify current pricing and limits before purchase.
Questions people ask
Can an AI detector prove that text was written by AI?
No detector score should be treated as proof on its own. Use a flag as a reason to review the text and context, not as a verdict. For consequential decisions, document the review process and give the writer a chance to respond.
How accurate are AI content detectors?
Accuracy depends on the text and the evaluation method. Vendor claims may use different samples or definitions, so they are not directly comparable by default. Look for a stated methodology, limitations and discussion of false positives before relying on a claim.
Can AI detectors produce false positives?
Yes. A detector may flag human-written text, so teams should decide in advance how flags are reviewed and appealed. Avoid automatic rejection based only on a score, and check whether the vendor explains uncertainty and provides guidance for interpreting results.
Which AI detector is best for SEO teams?
The right choice depends on volume, published plan limits, price and the review process your team can support. Compare current vendor terms and documentation, then shortlist tools whose stated limits fit your workload. Do not choose on an accuracy claim alone.