Last updated: September 3, 2026
Formula Log is made by Yeonwoo Lee and sold through the App Store. Your licence to use it is Apple's standard Licensed Application End User License Agreement, which you accept when you buy. This page is not a second contract — it explains in plain words what the app does with your work, what it depends on, and where its limits are. Nothing here takes away a right you have by law.
Formula Log is a one-time purchase, not a subscription. It unlocks the app on the Apple ID that bought it, and it does not expire. Backup and export are free for everyone — paying lifts the 15-client limit, and nothing else changes. Purchases, receipts, and refunds are handled by Apple under Apple's terms; we never see your payment details and cannot issue a refund ourselves. If Apple declines and you think the app didn't do what it says, email me — where the law gives you a remedy against me, I'll honour it.
Everything you type stays yours. We claim no rights over it, we cannot read it, and you can take it out at any time as a CSV, JSON, or PDF file. If you stop using the app, nothing of yours is held hostage.
Formula Log is a notebook. It stores what you choose to write down: products, developer volumes, processing times, notes. It is not a formulation tool, not a calculator, not a safety system, and not professional advice. It does not check, verify, correct, suggest, or approve anything you enter, and it cannot: it has no knowledge of the products you use, your client's history, their allergies, their scalp, what they had done last month, or what any mix will do to any particular head of hair.
A formula shown in this app is a note you once wrote, nothing more. It is not a recommendation to use it again, on that client or anyone else. Reusing it is a professional decision, and it is yours. Hair colour is a chemical service that can cause allergic reactions, chemical burns, breakage and scalp injury even when performed correctly, and the same formula on the same person can behave differently on a different day.
So, entirely and without exception: every decision about what to mix, what to change, what to refuse, when to patch test, and when to send someone to a doctor stays with you — exactly as it did when these notes lived on an index card in a drawer. Keep following your training, your licence, your insurance, your product manufacturers' instructions and safety data sheets, and the law where you work. Where anything you read in this app conflicts with any of those, they win and this app loses, every time.
We accept no responsibility for the outcome of any service, for any injury, reaction, or damage arising from a formula recorded in or read from this app, or for any decision taken with it in hand. That is not a limitation we are asking you to accept in exchange for something — it is a description of what this app is. It has no way to be responsible for a chemical service performed by a licensed professional in a room we are not in.
The app keeps your book on your phone, in recent snapshots on the device, and — once the iCloud backup is switched on for your account — mirrored to your own iCloud. That last one runs on Apple's iCloud service, which we do not own, operate, or control. If iCloud is signed out, switched off, out of space, unavailable, changed by Apple, or simply loses something, that is outside anything we can reach — the app will tell you on the Backup screen when your work is not reaching iCloud, and that notice is the warning to act on.
So, plainly: treat the backup as a safety net, not a vault. If a set of formulas would genuinely hurt to lose, export a file and keep it somewhere you control. Devices are lost, accounts fill up, and services have bad days. The export button exists for exactly that reason.
We build this carefully and we fix what we find, but no software is faultless. If Formula Log does not do what this page, the App Store listing, or the app itself says it does, tell us — that is a defect, and we will fix it, or you can ask Apple for your money back. The law where you live gives you rights about defective digital products; nothing here reduces them, and in the EU, the UK and Korea those rights apply whatever this page says.
What we do not promise is the part we do not run. The iCloud copy lives on Apple's service. If iCloud is signed out, full, unavailable, or loses something, we cannot reach it and cannot recover it for you. The app tells you on the Backup screen when your work is not reaching iCloud — that notice is the warning to act on, and the export file is the answer.
If you lose money or work because of something we got wrong, we take responsibility for it. Beyond that, we are not responsible for loss caused by iCloud, the App Store, your device, or anything else we do not operate, and not for indirect or consequential loss such as lost bookings.
These limits never apply to harm we cause intentionally or through gross negligence (고의 또는 중대한 과실), to personal injury, or to anything the law where you live says cannot be limited. In Korea, 약관의 규제에 관한 법률 applies to this page and overrides anything in it that conflicts.
A before/after photo is a picture of a real person, and what you write in a formula note is sometimes about their health — a reaction, a patch test, a scalp condition. Formula Log does not analyse either: photos are stored as pictures, never scanned or matched against a face, and notes are stored as text. That also means the app cannot tell when a note has become sensitive. Ask your client before you photograph them, and remember that in the EU, the UK and Korea anything you record about their health needs their clear agreement. Share cards and exports carry the photo and the notes with them — check what's in one before you send it.
Please don't try to break the purchase check, resell the app, or use it to store things that are illegal where you are. The free tier exists so you can try the app properly before paying; working around it is not what it is for.
If this page changes, the updated version is posted at this URL with a new "Last updated" date.
Formula Log is made in the Republic of Korea, and Korean law applies to this page. That never takes away the consumer protections of the country you live in: if your home law gives you more, your home law wins.
Questions about these terms: yeonwoo@kulvo.io