A diary is not like a to-do list. It's not like a calendar, or a note, or a shopping list. Those things have a lifespan of days or weeks. A diary has a lifespan of a lifetime. And that one difference changes everything about how it should be built.
The question nobody asks about diary apps
When people worry about diary apps, the conversation usually goes to privacy: "Can the company read my entries? Are they end-to-end encrypted?" These are fair questions. Most reputable apps will tell you yes, your data is encrypted, and they can't see it.
I actually believe them. That's not what kept me up at night.
What bothered me was a different question: Will I still be able to read my entries in 20 or 30 years?
The real problem: vendor lock-in over a lifetime
Think about the app landscape over the last decade. Services that seemed permanent — Google Reader, Evernote's best years, Day One's original model, countless journaling startups — have shut down, pivoted, been acquired, or changed their terms in ways that stranded users. That's a 10-year window. We're talking about a diary. Something you want to re-read at 50, 60, 70 years old.
The uncomfortable truth is that no company lasts 30 years unchanged. Startups get acquired. Business models shift. Servers get shut down. When that happens, if your diary data lives exclusively on their infrastructure — even if it's beautifully designed, even if it's encrypted — it can simply disappear. Or you get 30 days notice to export before the lights go off.
That's a catastrophic outcome for something as irreplaceable as a diary. You can't recreate a decade of daily reflections.
Why format matters as much as storage
Storing your data locally or in iCloud solves the infrastructure problem — your entries aren't at the mercy of a startup's runway. But that's only half the answer. The other half is format.
Opal stores every entry as a plain .md Markdown file. Not a proprietary database. Not a binary format that only one app can read. Plain text with light formatting — something a human can read in any text editor, on any operating system, with or without any app at all.
Markdown has been around since 2004 and is as close to a universal writing format as exists. Even if Opal stops being maintained tomorrow, even if Apple changes iCloud entirely, your diary entries will still be readable. Open them in Notes. In Obsidian. In VS Code. In any text editor on any computer, now or in 30 years.
The goal isn't just to keep your diary safe from other people reading it. It's to keep it safe from time itself.
What this means for how Opal is built
This philosophy shapes every decision in the app. No proprietary sync format — iCloud Drive handles sync as plain files. No account required — there's nothing to delete or lose access to. No backend servers — there's no company infrastructure that can shut down and take your data with it.
When you write in Opal, your entry is immediately a file. Right now, if you open the Files app on your iPhone, you can see it. Copy it. Email it to yourself. Open it in iA Writer. Back it up to a hard drive. It's already yours in the most literal sense possible — not "yours" as in you agreed to terms of service that say it's yours, but yours as in it's sitting in a folder with your name on it.
What Opal is not trying to be
Opal is deliberately minimal. No streak gamification, no social sharing, no web clipper. Not because those things are bad, but because every added layer of complexity is another potential point of failure over a 30-year horizon.
A diary should be a quiet, permanent place. The simpler the core, the longer it lasts. Any optional features built on top of that core — like AI summaries — are designed with the same privacy principle: your data never leaves your control. That means local models or bring-your-own-key, not a backend that reads your entries on our servers.
Opal is new — and I'm honest about that
I'll be straightforward: Opal is a new app, built by one person. It doesn't have thousands of reviews. There will be rough edges. But the core promise — that your entries are plain Markdown files stored on your own device, readable by any app, forever — is one I can actually keep. It's baked into the architecture, not a policy that can change.
If you've ever worried about what happens to your diary data long-term, I built Opal for you.
Thank you for reading. If you want to reach me directly, I'm at hello@opaldiary.app. I read every message.