GPTZero vs Undetectable AI (2026): which should you pick?
As of Nov 13, 2026, GPTZero grades higher than Undetectable AI: 2.4 against 2.2 out of 4.0.
Checked Nov 13, 2026 · graded Nov 13, 2026 by ToolGPA
GPTZero grades higher on the free plan and features. Undetectable AI grades higher on value for money. They get the same grade on ease of use and platforms.
Price, platforms and features side by side. The table says where each price was read and when.
GPTZero
AI-writing detector with plagiarism, writing replay and an API
Undetectable AI
AI humanizer and AI detector sold by monthly word allowance
Which one is for you
Pick GPTZero if
- Fits if you grade or review writing and want to check it for AI
- Works for teachers whose classes run on Canvas or Google Classroom
Look elsewhere if
- Tight if you check a lot: the free plan stops at 10,000 words a month
- Skip it if you want one clear price, because paid prices vary by region and by test
- Pricey if you want a team: two-seat minimum, and the API is priced separately
- Watch out: the vendor's own wording suggests a detector is a guide, not proof
Pick Undetectable AI if
- Fits if you need to rewrite short pieces and have a small word budget
- Works for people who also want a detector alongside
Look elsewhere if
- Tight if you try it first: the trial is 250 words
- Pricey if you write a lot, because plans are measured in words a month
- Watch out: $5 is the yearly rate; month-to-month the first plan is $9.99
- Watch out: non-expiring credits and white labelling are on the custom business plan only
How we grade them
| 2.4GPAGPTZeroFair | 2.2GPAUndetectable AIFair | |
|---|---|---|
| Value for money | CNo single US dollar list price could be read, and prices vary by region. Left in the middle of the category. | B$5 a month billed annually for 10,000 words, inside the category's cheapest quarter at $5.75. Month-to-month it's $9.99, around the middle. |
| Free plan and trial | CA free plan up to 10,000 words a month, which a regular user will hit. | DA free trial capped at 250 words, and the listing doesn't say whether a card is needed. |
| Features | BAI detection, writing replay, plagiarism, grammar feedback, a hallucination checker and an API. Nothing in the listing shows a gap in the core job. | CHumanizer, detector, writing tools and a refund if flagged. It covers the job, with a word budget attached. |
| Ease of use | CNo store rating on record. You make an account and connect it to Docs or a class system. | CNo store rating on record. Pasting text in is quick, but results need checking. |
| Platforms and integrations | BWeb and a Chrome extension, with Google Docs, Canvas, Google Classroom, Gmail and an API. | BWeb and a Chrome extension, with an API. |
| Best for | checking whether text looks AI-written | rewriting text so it passes AI detectors |
The GPA is the average of the five grades: an A is 4 points, an F is none. The full reasons are on each tool's page: GPTZero and Undetectable AI. How we grade
Where they differ
- GPTZero also covers grammar & style.
- Undetectable AI also covers documents.
At a glance
| GPTZero | Undetectable AI | |
|---|---|---|
| Pricing | Free plan | Free trial |
| Starts at | Not published | $5 per month for 10K words, billed annually ($9.99 billed monthly) |
| Free plan | Free plan covering up to 10,000 words per month, according to the vendor's pricing FAQ. | None |
| Free trial | None listed | Free trial limited to 250 words; more use needs a paid plan |
| Web | ||
| Browser extension | ||
| Made by | GPTZero | Undetectable Inc. |
| Price read from | Not confirmed | undetectable.ai |
| Checked | Nov 13, 2026 | Nov 13, 2026 |
Worth knowing
GPTZero
- Paid individual plan prices vary by region and by test; no single US dollar list price could be read.
- The free plan stops at 10,000 words a month.
- The team plan has a two-seat minimum and gives 500,000 words per member each month.
- The API is priced separately from the individual and team plans.
Undetectable AI
- The free trial is capped at 250 words.
- Plans are measured in words per month, so heavy users move to the larger tiers quickly.
- The $5 figure is the yearly-billing rate with a crossed-out $9.99; month-to-month the first plan is $9.99.
- Non-expiring credits and white labeling are offered only on the custom business plan.
Key features
GPTZero
- AI detection
- Classifies text from models such as ChatGPT, Claude, Gemini and Llama; an Advanced Scan shows how different sentences score.
- Writing replay in Google Docs
- The Chrome extension records a replay of a document being written, including copy and pastes and unusual typing patterns.
- Plagiarism checker
- Checks whether content was copied from outside sources without attribution.
- Writing feedback and grammar check
- Gives feedback on clarity, tone and wordiness beyond a basic grammar check.
- Hallucination detector
- A separate checker aimed at hallucinated content in AI-written text, listed beside the AI detector.
- Classroom and API integrations
- Connects to Canvas and Google Classroom, and offers an API with code samples in 17 languages.
Undetectable AI
- AI humanizer
- Rewrites AI-generated text with the aim of passing AI detectors, with writing-level matching.
- AI detector
- Paid plans list unlimited AI detecting. Separate detectors exist for images, voice, video, deepfakes and fake PDFs, receipts and IDs.
- Writing tools
- The site also lists an essay writer, stealth writer, paraphrasing tool, SEO content writer, plagiarism checker and a human auto-typer.
- Refund if flagged
- The pricing page says the cost of a humanization is refunded if the output is flagged as not human; details are on the Help pages.
- API and Chrome extension
- Plans are marked API compatible, and the site lists a Chrome extension.
Plans
GPTZero
Pricing could not be confirmed. See gptzero.me.
Undetectable AI
10K words$5
per month for 10,000 words, billed annually ($9.99 billed monthly)
10,000 words a month, charged $60 a year. The page crosses out $9.99 and marks yearly billing as 50% off.
20K words$9.50
per month for 20,000 words, billed annually ($19 billed monthly)
20,000 words a month, charged $114 a year.
35K words$15.75
per month for 35,000 words, billed annually ($31 billed monthly)
35,000 words a month, charged $189 a year.
50K words$21.25
per month for 50,000 words, billed annually ($42.50 billed monthly)
50,000 words a month. Larger allowances up to 380,000 words are listed, with custom pricing on request.
Ways to pay less
GPTZero
No public discounts listed.
Undetectable AI
- Annual discount
Yearly billing at half the monthly price
The pricing page marks yearly billing as 50% off the monthly rate, for example $60 a year for 10,000 words a month.
Common questions
Which is cheaper, GPTZero or Undetectable AI?
As of Nov 13, 2026, GPTZero has no price we could confirm, and Undetectable AI starts at $5 per month for 10K words, billed annually ($9.99 billed monthly).
Which has a free plan, GPTZero or Undetectable AI?
As of Nov 13, 2026, only GPTZero has a free plan. Undetectable AI does not, though it has a free trial.
More comparisons
How this page was made
- The verdict at the top follows a fixed rule. When both tools are in the same category and either is in our top three for it, the verdict follows that ranking: the higher-placed tool is our pick. The top three weigh who each tool suits as well as its grades, so a pick can go against the GPA. Otherwise the page does not pick one and says which grades higher: the higher GPA first; on a tie, the one with a free plan, then the one that starts cheaper in dollars a month, counted the same way for both; if they are still level, what the choice depends on.
- The grades are our own, from each tool’s review or report card. The GPA is their average.
- Prices, plans and platforms come from each tool’s listing. The table above says where each price was read and when.
- The differences and the answers to the questions are worked out from those listings.