Try Checkpoint on your iPhone.
Install the latest iOS build through TestFlight while the App Store listing is being prepared. TestFlight is Apple’s official way to distribute app builds before public release.
How to install it (first time)
If you have never used TestFlight, do not worry. It takes about two minutes. Follow these steps on your iPhone, in order.
- 1
Tap the button above on your iPhone.
If you are reading this on a computer, send yourself the link and open it on the phone. The button will try to open the TestFlight app. The first time, you probably do not have it yet — that is fine, the next step fixes that. - 2
Install TestFlight from the App Store.
If your phone says “TestFlight is required” or asks you to get the app, tap Get / Install. You may need to confirm with Face ID, Touch ID, or your Apple ID password. TestFlight is made by Apple and is safe. - 3
Come back here and tap the button again.
Once TestFlight is installed, tap Open the TestFlight invite at the top of this page one more time. It will now open inside TestFlight instead of your browser. - 4
Tap Accept, then Install.
TestFlight will show a screen titled Checkpoint. Tap Accept, then tap Install. A blue dot next to the app means it is installed through TestFlight — that is expected. - 5
Open Checkpoint and sign in.
You can now open Checkpoint from your home screen like any other app. Create an account or sign in with the same email you use everywhere. That is it — you are in.
Tell me what is broken. Tell me what is missing.
Checkpoint is a small one-person operation. There are no QA testers, no support team, and no way for me to know what is wrong on your phone unless you tell me. Every bug report and every “this is confusing” note from you genuinely changes what I build next week.
You are not bothering me. You are the reason the app gets good. If something feels weird, broken, slow, ugly, or just wrong — please say so. There are no stupid reports.
How to send feedback
Pick whichever is easiest. They all reach me.
Take a screenshot, then share it.
When something looks wrong inside Checkpoint, take a screenshot the normal way (press the side button + volume-up at the same time). TestFlight will ask if you want to send the screenshot as feedback. Tap Share Beta Feedback, type a sentence or two, and send. It comes straight to me.
Open TestFlight and tap “Send Beta Feedback.”
Open the TestFlight app, tap Checkpoint, scroll down, and tap Send Beta Feedback. You can type freely and attach screenshots from your camera roll.
hello@checkpoint.study
When in doubt, just email. A photo of the screen with your finger pointing at the problem is a perfectly good bug report. So is “the app crashed when I tapped the green button this morning.”
What is worth reporting?
Anything. Truly. To make it easier, here are some things I genuinely want to hear:
- Bugs. Anything that crashes, freezes, shows the wrong thing, or just looks broken.
- Confusing moments. If you ever thought “wait, what do I do here?” — that is a bug in the design, and I want to know.
- Wrong Japanese. If a translation or sentence looks off, please flag it. I would rather fix one now than ship it to everyone later.
- Feature requests. “I wish it could…” is one of the most useful sentences you can send.
- What you liked. Knowing which moments felt good helps me know what to do more of.
A positive App Store review helps a lot.
Once the App Store page is live, leaving a positive review is one of the best ways to help other Japanese learners discover Checkpoint. Mention what helped you most — SRS reviews, kana drills, grammar practice, AI Tutor, or progress tracking.
Still send bugs and confusing moments as feedback. Reviews help people find the app; feedback helps us make it better.
A couple of small notes
- · TestFlight builds expire after 90 days. If the app stops opening, come back to this page and accept the latest invite — your progress is safe.