Why free AI detectors (Zhuque, ZeroGPT) are not enough
TL;DR Free tools are a warm-up. A full English paper, paragraph-level edits, paper safety, and one-click retest need a paid product. PaperMirror uses free quota to acquire, and rewrite credits to earn — on purpose.
Tencent Zhuque made short Chinese detection free. ZeroGPT made English paste free. They finish acquisition, not the assignment. Here are the walls free tools hit the night before a due date.
The length wall
Zhuque caps a few thousand characters; ZeroGPT is poor on long documents. A 2,500-word essay already overflows, let alone a dissertation chapter. PaperMirror takes 20,000 characters per run, bills actual characters, and treats long papers as first-class.
No rewrite loop
Free sites tell you “this sounds like AI” and stop. You either hand-edit until dawn or open a humanizer of unknown origin. PaperMirror one-click rewrites and retests on the same report.
The report does not look like the instructor’s
Heatmaps look good. Instructors open a Turnitin-style overall rate plus span highlights. The closer a self-check is to that reading, the better you know what to edit. That is why we align an in-house engine with that reading.
Safety and ads
Free pages live on ads and data. Coursework may contain unpublished results. PaperMirror’s promise — not stored in a corpus, reports visible only to you — is a promise that only holds if we charge.
How we use free as a door
- Homepage guest trial of 1,000 characters, so this is not an empty site.
- Signed-in users get another 1,000 free characters per day.
- New users get 1,000 credits, enough for one more serious short scan.
- Overflow and rewrite go through credit packs. You pay for what you use.
Warm up free, finish the loop paid
Try a scan first. Top up when you need to rewrite the red band. You do not have to start at ¥100.
Try a free scanDetection and rewrite are for pre-submit self-checks. Follow your school's integrity policy. PaperMirror is not Turnitin or CNKI. The school system is the source of truth.