You want detection and rewriting free, together
Penlify's free plan includes 3 detections and 5 rewrites a month in the same workspace — no upgrade required to act on a flagged sentence.
The short answer
Choose ZeroGPT if you want one free toolkit that also checks plagiarism, grammar, and images. Choose Penlify if you want the AI-detection result to hand you a rewrite of the flagged sentences without paying for a separate tier.
You want one toolkit for many checks
Plagiarism, grammar, summarizing, translation, and image/video AI detection are bundled alongside its detector — useful if you want fewer tabs open for unrelated tasks.
Feature and pricing comparison
Numbers below are read directly from ZeroGPT's pricing page, not estimated.
| Area | Penlify | ZeroGPT |
|---|---|---|
| Free plan detection | 3 detections/month, sentence-level scoring. | Up to 15,000 characters per check, no card required. |
| Free plan rewriting | 5 rewrites/month included free. | Not included — "Humanize AI generated text" is listed only on paid plans. |
| Cheapest plan with rewriting | $2.99/mo or $24.99/yr (~$2.08/mo), unlimited. | PRO: $9.99/mo billed annually ($13.99/mo monthly), 100,000 characters/check. |
| Fixing a flagged passage | Rewrite the flagged sentence directly in the same workspace. | Separate "AI Humanizer" tool from the detector; not a scoped flag-to-rewrite step. |
| Plagiarism checking | Not offered. | Built in, word-limited by plan (300 words one-time on Free tier shown in the plan comparison table). |
| Other bundled tools | None — detection and rewriting only. | Grammar checker, summarizer, translator, dictionary, image and video AI detectors. |
| Built for | A writer checking and fixing their own draft. | Anyone wanting one broad, free AI-content toolkit. |
Honest tradeoff: ZeroGPT's free detector is genuinely generous on volume, and its bundled toolkit covers more ground than Penlify ever tries to. What it doesn't give away free is the fix — humanizing text is a paid-plan feature there. Penlify's whole free tier is built around not needing to upgrade just to rewrite what got flagged.
Pricing and feature limits checked against ZeroGPT's official pricing page on 28 August 2026. Plans and pricing can change.
Why "free AI detector" doesn't always mean "free fix"
ZeroGPT's free plan is a real free plan — 15,000 characters per detection check, no card, and according to its own plan-comparison table a monthly allowance in the hundreds of thousands of words. For a one-off check on a document, that's plenty.
The gap shows up right after the score. ZeroGPT lists its AI Humanizer as a feature of the PRO tier and above — the cheapest of which is $9.99 a month billed annually. So a flagged document on the free plan tells you there's a problem, and checking that box costs a subscription to fix it.
Penlify built the free tier around that exact moment instead. Three detections and five rewrites a month cost nothing, so seeing which sentence is the problem and getting a rewritten version to review both happen without a card on file. The tradeoff is scope: Penlify doesn't check plagiarism, grammar, or translate anything. It's built to do one thing — detect and fix a writer's own draft — and give that away free.
Common questions
Is ZeroGPT's free plan enough to rewrite flagged text?
Not for rewriting. ZeroGPT's free plan covers AI detection (up to 15,000 characters per check), but its AI Humanizer is listed as a paid-plan feature starting at $9.99 a month billed annually. Penlify's free plan includes both detection and rewriting — 3 detections and 5 rewrites a month, no card required.
Does ZeroGPT check plagiarism too?
Yes. ZeroGPT bundles a plagiarism checker, grammar checker, summarizer, translator, and image/video AI detection alongside its core AI detector. Penlify does not check plagiarism — it focuses on AI-pattern detection and rewriting a writer's own draft.
How much does ZeroGPT cost compared to Penlify?
ZeroGPT's cheapest paid tier (PRO) is $9.99/month billed annually, or $13.99/month billed monthly, and that's the tier where its AI Humanizer unlocks. Penlify's paid plan is $2.99/month or $24.99/year (about $2.08/month) for unlimited detection and rewriting.
Test the workflow with your own draft
Start with the private analyzer. It gives value without requiring an account or sending the text to Penlify.