CertRx: the miss is the product.
Free, mobile-first certification practice that diagnoses the misconception behind a wrong answer before it reveals the right one.
Practice apps grade you and move on. You pick B, the app says the answer was C, and the single most teachable moment in the session gets skipped. Learners grind hundreds of questions and keep making the same category of mistake, because nothing ever names the mistake.
When a learner misses a question, CertRx asks why they picked what they picked. An AI reads their typed reasoning and diagnoses the specific misconception before the correct answer is revealed. Five remediation panels are generated at runtime from the learner's own words: what you got right, the mix-up, why this trips people up, in the field, and study this next.
The AI is grounded, not freestyling. Every question carries authored fields: a reinforcement note for correct answers, a note on why each wrong option is wrong, the tested concept, and an official objective reference. The runtime diagnosis builds on that scaffolding, so remediation works for every question without anyone hand-writing it.
- React + Vite frontend on Cloudflare Pages.
- Pages Functions make every AI call server-side through Workers AI. No keys or model ids in the browser.
- Cloudflare KV handles soft rate limiting and anonymous most-missed counters.
- One JSON data file per certification, dynamically imported, so each cert ships as its own chunk. Adding a cert is a data file, not a rewrite.
No account, no popups, no tracking. Answers stay on the device. The only server-side state is an anonymous counter of most-missed questions.
- 11 live cert banks
- 2,550 original questions
- 40+ exams in the target catalog
Security+ (SY0-701) shipped first. The catalog spans CompTIA, AWS, Microsoft, Cisco, ISC2, ISACA, Google Cloud, and NVIDIA. All questions are original and test the publicly published exam objectives; nothing reproduces real exam items or commercial question banks.