A few quiet minutes with yourself, every day
HiDay
Hello, Today.
A security-first journal that greets you with a different sentence every time — woven from the hour, the weather, and your recent days. Your entries never leave the phone, and sync seamlessly across all four Apple and Android platforms.
Security first — the basis of every decision
Your journal never
leaves your phone.
This isn't marketing copy — it's the architecture. HiDay does not own a server that could receive your entries. All journal bodies are stored only in an encrypted SQLite database on your device (SQLCipher · AES-256), and any sync runs only through your own cloud (iCloud / Google Drive).
Encrypted local DB
The whole journal database is encrypted with SQLCipher (AES-256). The key lives only in the OS keystore — iOS Keychain / Android EncryptedSharedPreferences / macOS Keychain.
App lock (biometric)
Lock the app behind Face ID, Touch ID, fingerprint, or device PIN. Re-authenticates each time you return from background — safe even if you hand the phone over.
PIN-encrypted sync
Optionally encrypt the body once more before it touches iCloud / Drive — PBKDF2 (100k) + AES-256-GCM, derived from a 6-digit PIN. We don't know the PIN either.
No developer server · No accounts · No telemetryAfter install, the app talks to none of our servers — because they don't exist. No accounts, no logins, no analytics SDKs, no crash collection. Your entries never leave the device.
Bodies live only in the encrypted local DBEvery entry and metadata row is stored inside the app's private SQLCipher AES-256 database. No other app can read it.
Sync routes only through your own cloud (iCloud / Google Drive)iOS / iPadOS / macOS use your iCloud Private Database. Android uses your Google Drive App Folder. We are not in the path either way.
Optional PIN encryption — even the cloud only sees ciphertextTurn this on and the body is encrypted again with AES-256-GCM right before it's pushed. iCloud / Drive only see ciphertext, and without your PIN nothing decrypts.
App lock — Face ID · Touch ID · fingerprintRe-authenticate every time the app comes back from background. If someone borrows your unlocked phone, they still cannot read your journal.
Location is one-shot, weather only (coordinates, not entries)When you open the home screen, GPS coordinates are fetched once and sent to OpenWeatherMap. The journal body is never attached, the coordinates are not stored, and there's no background tracking.
BYOK — AI features only with your own key (optional)If you turn on AI features, calls go directly from the device to Gemini using your own API key. The key stays in the OS keystore. Nothing routes through us; if you turn AI off, nothing is called at all.
Delete the app = delete everythingRemoving the app wipes journals, metadata, and BYOK keys from the device. Your sync folder in iCloud / Drive is yours to delete on your own.
No ads · no tracking SDKsNo AdMob, Facebook SDK, Mixpanel, Amplitude, Crashlytics — none of them.
Data flow — drawn out
⚠️ Where your responsibility starts
If you sync to iCloud / Google Drive, that cloud's security is between you and the cloud provider (we recommend 2FA). And if you turn on PIN encryption, losing the PIN means the data is unrecoverable — the key is derived only from the PIN, and we cannot help you. Keep the PIN somewhere safe outside the app.
How it works
It does three things, every day
When you open the app, a one-line greeting arrives first — chosen for the hour, the weather, and your recent days. Then you write or speak the day.
Greet
Time of day (dawn / morning / day / evening / night) + weather (clear, cloudy, rain, snow, thunder, heat, cold) + the shape of your recent entries → a different sentence every time, read aloud. The top-right shows a forecast-driven, hour-by-hour weather animation (Lottie).
Write
"Speak" takes your voice and turns it into text. "Write" is the keyboard. Either way, the city / district, the weather, the temperature and the wind are saved with the entry automatically.
Look back
"On this day a year ago" surfaces the same date from past years. Search lets you find words inside any entry. With an AI key, HiDay picks an old entry at random and writes a one-line story of remembrance.
Features
Everything you get
Core journaling is free, forever. AI features run on your own Gemini key (BYOK) and unlock under Pro mode — and the first 1 month of Pro are free for everyone.
- Time- & weather-aware greetingsFree
- Forecast-driven hourly weather animation (Lottie)Free
- Voice journaling (STT) · Text journalingFree
- Auto-attached weather (condition · temp · wind · city)Free
- Entry list · detail · "add another line"Free
- Full-text search across entriesFree
- On this day a year ago — same-date entries from past yearsFree
- App lock — Face ID / Touch ID / fingerprint / device PINFree
- iCloud sync — iPhone · iPad · Mac, both directionsFree
- Google Drive sync — Android phones / tablets, both directionsFree
- PIN-encrypted sync — bodies in the cloud are encrypted againFree
- Frosted glass UI — cards floating over a photo, blurred like real glassFree
- Rotating photo backgrounds — 7 bundled landscapes, plus your ownFree
- Typewriter cursor — a small visual tick as each character landsFree
- 한국어 / English UIFree
- Native macOS window (hover-revealed traffic lights)Free
- Old Friend mode — one-line check-in based on your past entries (AI)Pro · BYOK
- AI insights — weekly recap, pattern reflection (AI)Pro · BYOK
- AI voice — natural-sounding spoken greeting (Gemini TTS)Pro · BYOK
- Random recall story — AI-written one-liner from an old entryPro · BYOK
Extras when you bring an AI key
Add a Gemini key,
and the journal starts to remember.
HiDay is BYOK (Bring Your Own Key) — calls go straight from your device to Gemini using a key you own. No developer server in the path; the key lives in the OS keystore. Daily journaling fits comfortably inside Gemini's free tier.
Old Friend mode
Reads from the last 30 / 90 / 365 days and offers a one-line check-in tuned to today: "You haven't been sleeping much — how's tonight?"
AI insights
Weekly recap, mood patterns, recurring words — only when you ask for them. Watch your own usage in your own console.
AI voice
Gemini TTS reads the greeting in a warm, natural voice (Kore, Puck, etc.) — much closer to a real person than the default system voice, in both Korean and English.
Random recall story
Pick one entry older than a year, at random, and turn it into a single line of remembrance. A spring afternoon you'd forgotten suddenly comes back.
💡 Gemini's free tier is more than enough for daily use
Google Gemini has a real free tier that comfortably covers journaling. No card required — a Google account is enough.
| Model | Per minute | Per day | HiDay daily use |
|---|---|---|---|
| Gemini 2.5 Flash | 15 | 1,500 | ~3-10 calls |
| Gemini 2.0 Flash | 15 | 1,500 | ~3-10 calls |
(One entry + one daily AI reflection + one spoken greeting ≈ 3-10 calls.) A whole month of normal use barely scratches 1% of the daily quota. Get a key in about a minute at Google AI Studio.
Pricing
1 free month, then you decide.
Core journaling is free forever. Pro features (the entire AI side) unlock for everyone for the first 1 month after you launch the app — with no signup and no card on file. After 1 month, only the Pro features lock; the free journaling stays exactly as it is.
First 1 month — free
Every Pro feature plus everything in Free. No signup, no card.
- All free features (journaling · sync · app lock · weather)
- Old Friend mode (BYOK)
- AI insights (BYOK)
- AI voice (BYOK)
- Random recall story (BYOK)
After 1 month, the free journaling continues unchanged; only Pro features lock. Pro subscription: $4.99 / year, auto-renewing (in-app purchase · cancel anytime in your Apple ID or Google account settings).
Where it runs
Write once, see it everywhere.
Same UX, same security model, all four platforms — built on a single Flutter codebase with native window chrome where it matters.
💡 MacBooks have no GPS, but the weather still works — Wi-Fi-based location, then IP-based city/country fallback. If you deny permission, the chip simply stays empty (graceful degrade).
FAQ
Frequently asked
Why does HiDay want location?
To fetch the day's weather, and only that. On launch, we ask for GPS coordinates once and send them to OpenWeatherMap. Coordinates are not stored, and they never travel with the journal body. If you deny permission, the journal still works — the weather chip just stays empty.
Does the AI feature send my entries to OpenAI / Google?
Only when you turn on BYOK and explicitly ask for an AI feature. Calls go from the device to Gemini's official API using the key you typed in. What that company does with the call is governed by their terms — our developer server is not in the path at all. Turn AI off, and nothing is called.
Is iCloud / Google Drive sync safe?
Two layers of protection. (1) Data only goes to your cloud — iCloud's Private Database (only your Apple ID can access it) and Google Drive's App Folder (no other app, even your other apps, can see it). (2) Turn on "PIN-encrypted sync" and the body is encrypted with AES-256-GCM before it ever leaves the device — the cloud only ever stores ciphertext, undecryptable without the PIN.
What happens if I forget the PIN?
It is unrecoverable. The PIN is the only input to key derivation (PBKDF2 · 100k iterations), and we don't store it anywhere. Without the PIN, encrypted bodies can't be opened. This is by design — but it does put the responsibility on you. Keep the PIN written down somewhere safe, outside the app.
What's the threat model?
The realistic risks, and what we do about them:
(1) Someone takes your unlocked phone. Turn on App Lock — Face ID / Touch ID / fingerprint / device PIN every time the app returns from background. Even with the phone unlocked, your journal stays closed.
(2) Your iCloud / Google account leaks. If sync is on, that's a real exposure. We recommend 2FA, plus the PIN-encryption option so the body stays opaque even if the cloud is reached.
(3) Your BYOK key leaks. Keys live in the OS keystore, but a rooted/jailbroken device could expose them. Watch usage in the AI provider's console.
None of these route through us — because there is no "us" in the path.
Is the security the same on iPhone and Android?
Same design, different OS primitives:
iOS uses Keychain · App Group Sandbox · iCloud Private DB. Android uses EncryptedSharedPreferences (Jetpack Security) · Internal Storage · Google Drive App Folder. In both cases, no other app and no other user can reach your data. The cryptography itself (SQLCipher · AES-256) is identical across both.
Does the journal lock when the trial ends?
No. Writing, reading, searching, syncing, and the app lock are free forever. What locks after the 1-month trial is only the AI side — Old Friend mode, AI insights, AI voice, random recall story. Subscribe ($4.99 / year, auto-renewing) and they re-activate.
Legal / regulatory posture (privacy law, GDPR)?
HiDay does not collect, store, or process user data on our side. So as a developer we have no personal-data processing — no controller / processor obligations under GDPR / CCPA / Korea's PIPA. All data control sits with you. The privacy policy is here.