GPTZero vs Undetectable AI

GPTZero

One of the detectors schools most often adopt, and the sentence-level highlighting is what makes a result usable in a conversation with a student rather than a bare percentage. No detector is evidence of authorship, though, and the cheap Essential tier is gone from the pricing page, so paid use now starts at Premium.

Pros

• +Sentence-level highlighting shows what drove the score instead of a bare percentage
• +Batch uploads and a developer API make it usable inside an existing review workflow
• +Free tier is generous enough to evaluate properly before paying

Cons

• −The Essential tier has been dropped, so the cheapest paid plan is Premium at $12.99 a month on annual billing or $23.99 month to month
• −The developer API is priced separately from the writing plans, starting at $45 a month
• −Word-metered quotas punish long documents disproportionately
• −Detection accuracy remains contested and the tool cannot prove authorship

Undetectable AI

Buy it only if you accept that passing a detector is a moving target: detector vendors retrain constantly, and text that cleared last month can flag next month. As a multi-format detection dashboard it is more defensible than as a bypass tool.

Pros

• +Detector and rewriter run in one pass, so you see which sentences changed and why
• +Coverage extends past text into image, voice, video and document classifiers
• +Browser extension works inside Docs and Gmail rather than a separate tab
• +Entry tier is genuinely cheap at annual rates

Cons

• −Rewrites often flatten voice and add filler to break statistical patterns
• −Detection on short passages is unreliable in both directions
• −Word quotas drain fast because rejected attempts still consume them
• −The free trial caps at 250 words, barely enough to judge output quality

Is GPTZero cheaper than Undetectable AI?

On published entry prices, Undetectable AI starts lower — $9.99/mo against $12.99/mo for GPTZero. Entry price is the lowest paid plan as we last verified it; what each plan includes differs.

Does GPTZero or Undetectable AI have a free tier?

Both: GPTZero has a free tier, and Undetectable AI has a free tier.

Which has a public API, GPTZero or Undetectable AI?

Both ship a public API, so either can be built on; the fact table above shows the platforms each one runs on.