Side-by-side comparison · Writing & Translation

GPTZero vs Undetectable AI

Everything that matters when choosing between them, in one place: our rating, what each can do, what they cost, and the trade-offs.

Best overall

GPTZero

4.2

From $0

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Undetectable AI

3.6

From $0

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Comparing 2 tools. Add one more if you like.

At a glance

GPTZero4.2

Best overallBest valueEasiest to use

Pick it if: Teachers, editors and business owners who want a second opinion on whether writing they've been handed came from AI.

Undetectable AI3.6

Pick it if: Marketers and writers who use AI for first drafts and want them to sound less robotic.

Overview

Attribute	GPTZero	Undetectable AI
In one line	Checks whether text was written by AI, with plagiarism and citation checks too.	Rewrites AI-written text so it reads more human and is less likely to get flagged.
Pricing model	Freemium	Freemium
Starting price	$0	$0
Free plan	Yes	Yes
Works with Claude Code	Yes	Yes

Rating breakdown

Our scores out of 5. The higher bar in each row is highlighted.

Attribute	GPTZero	Undetectable AI
Overall rating	4.2Winner	3.6
Ease of useHow quickly someone non-technical gets value from it.	4.5	4.0
FeaturesHow completely it covers its own job, and how well the pieces fit together.	4.5	3.5
Output qualityHow good the results are before you fix them.	3.5	3.0
Value for moneyWhat you get for the price, including the free plan.	4.0	3.5
Speed & reliabilityHow fast it is and how often it falls over.	4.5	4.0

Feature comparison

A tick means it does this today. A dash means we haven't checked.

Attribute	GPTZero	Undetectable AI
Access & platform
Free plan	Yes	Yes
Mobile app	No	No
Desktop app	–	–
Browser extension	Yes	Yes
API access	Yes	Yes
Teams & business
Team workspace	Yes	No
Enterprise plan or SSO	Yes	–
Connects to other apps	Yes	No
Open source or self-hosted	No	No
AI abilities
Works with your files	Yes	Yes
Understands images	–	Yes
Makes images	No	No
Makes video	No	No
Writes code	No	No
Runs agents or automations	No	No
Learns your brand or style	–	–
Works in many languages	Yes	Yes
Capabilities score	8/ 17	6/ 17

Pricing

Plans as listed on each vendor's site when we last checked. Confirm before you buy.

Attribute	GPTZero	Undetectable AI
Plans	Free $0 Checking the odd document.	Free $0 Testing one short piece.
	PremiumOur pick $23.99/mo, or $12.99/mo billed yearly Teachers and editors checking work every week.	10K words $9.99/mo, or $5/mo billed yearly ($60) Occasional use.
	Professional $45.99/mo, or $24.99/mo billed yearly Agencies and heavy users scanning lots of files.	20K wordsOur pick $19/mo, or $9.50/mo billed yearly ($114) Regular blog content.
	Team Professional price per seat, 2 seats minimum Schools and businesses buying for a group.	Larger plans From $31/mo, or $15.75/mo billed yearly Agencies and high volume.
Which plan to pick	Start on Free. If you check more than a few documents a week, Premium on yearly billing is the sweet spot. Professional only makes sense if you scan big batches of files.	Test the free 250 words on your own writing first. If the output works for you, a small yearly plan is cheap. Word credits reset monthly, so don't buy more than you use.

Key features

Attribute	GPTZero	Undetectable AI
Standout features	AI detection Plagiarism check Writing replay Citation and hallucination check Batch scans API and school integrations	AI humaniser AI detector Human typer Image and video detectors API

Pros and cons

Attribute	GPTZero	Undetectable AI
Pros	Clear sentence-level highlights, so you see exactly what looks AI-written Generous free plan for occasional checks Writing replay gives honest writers a way to prove their work Flags made-up citations, which most detectors don't API and batch scans for larger volumes	Simple: paste, pick a level, rewrite Built-in detector shows how text might score Cheap on yearly plans API for bulk rewriting Refund on humanised text that gets flagged
Cons	False positives happen, and short or formal writing gets flagged more often Edited or reworded AI text can get past it The best scan and plagiarism checks need a paid plan Mostly designed around schools, so some features won't matter to a business	No guarantee text will pass detectors Rewrites can read awkwardly or change your meaning Using it to hide AI use can break school or client rules Free trial is only 250 words Its marketing promises more than any humaniser can deliver

Who each one is for

Attribute	GPTZero	Undetectable AI
Best for	Checking essays and assignments for AI writing Screening freelance or agency content Spotting made-up citations in reports Showing you wrote a document yourself	Making AI drafts sound less robotic Seeing how detectors might score your text Rewriting at a set reading level Bulk rewriting through the API
You'll find it used by	Teachers Editors Content agencies Recruiters Students	Content marketers Bloggers Freelance writers SEO agencies Students

Questions people ask

Which is better, GPTZero or Undetectable AI?

GPTZero scores highest overall in our ratings (GPTZero 4.2/5 and Undetectable AI 3.6/5). GPTZero is best for checking essays and assignments for AI writing and screening freelance or agency content. Undetectable AI is best for Making AI drafts sound less robotic and seeing how detectors might score your text.

Which is cheaper, GPTZero or Undetectable AI?

GPTZero: There's a free plan, and paid plans start at $0. Undetectable AI: There's a free plan, and paid plans start at $0.

Which is easier to use, GPTZero or Undetectable AI?

GPTZero rates highest for ease of use in our scores. Teachers, editors and business owners who want a second opinion on whether writing they've been handed came from AI.

Ratings are our own, from using each tool, across ease of use, features, output quality, value for money, speed & reliability.

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