Short answer: A desktop diary app should store entries locally, encrypt them before writing to disk, work without a network connection, and export to JSON or Markdown. These four properties protect your writing regardless of what happens to the app or the company behind it.
If you are looking for a desktop diary app specifically, you probably already know you do not want a web interface or a mobile-first product that happens to run on a desktop. The harder question is what to actually look for once you have ruled those out.
Most comparisons of journaling apps focus on features: themes, tags, calendar views, word count statistics. Those matter for daily use. They do not tell you whether your writing will be accessible or safe five years from now. For a diary, that question matters more than it does for other categories of software.
This article covers the structural properties that separate a solid desktop diary app from a cloud-connected notes tool, and what to check before committing years of writing to any of them.
Why desktop is the right starting point for private journaling
Writing at a desktop has practical advantages that matter for a diary specifically. A full keyboard and a large screen make sustained writing easier. The file system is accessible, meaning you can locate the journal database, copy it to a backup drive, and understand where your data actually lives.
A desktop app can also run without a network connection, which is not a given for browser-based tools or apps built around cloud sync. If you write during travel or on a machine that is intentionally offline, that matters.
None of this is nostalgia for older technology. It is about choosing an environment that fits the writing habit you want to build.
The storage model is the most important decision
More consequential than any feature is where the diary entries actually live.
A cloud-first app stores entries on a server. The local copy, if one exists, is a sync cache. Your continued access to your own writing depends on the service staying available, maintaining your account, and not changing its terms in ways that affect stored data. If the company is acquired, shuts down, or removes your region's support, access can disappear. The cloud is also subject to policy decisions you have no control over, including how entries might be processed by AI features added in future updates.
A local-first desktop diary stores the primary copy on your machine. The journal file lives in a folder you can find and back up. Reading your entries five years from now does not depend on any server being online or any company remaining in business.
For private, long-term writing, local-first storage is the right default.
Encryption at rest, specifically
A password lock screen is not the same as encryption. Many apps ask for a password when opening but store the underlying database as plaintext. Anyone with access to the file can read the entries without knowing the password.
Encryption at rest means entries are encrypted before they are written to the database file on disk. The file contains ciphertext. Without the decryption key, the data is unreadable regardless of how the file is accessed.
The practical check: copy the database file to another machine and try to open it in a database viewer. If you can read entry text, the app does not encrypt at rest. If the file contains only ciphertext, it does.
For modern apps, AES-256-GCM is the standard cipher. An app that specifies neither the algorithm nor that encryption happens before disk writes is not making a useful claim about your data's security.
Cross-platform support
If you ever change operating systems, platform coverage becomes a practical concern. A diary app that runs only on macOS creates a problem the day you move to a Windows or Linux machine. A Windows-only app does the same in reverse.
The stronger default is an app that uses the same codebase and the same storage format on all major desktop platforms. That way, switching machines or operating systems is a file copy, not a migration project.
Export formats and the exit path
Export capability is not a backup feature. It is the clearest signal that an app treats your writing as yours.
JSON and Markdown are the two most portable output formats. JSON is machine-readable and preserves structure well enough to import into other tools. Markdown is human-readable and compatible with most text editors, static site generators, and knowledge management tools.
If an app can export both, you can leave without losing anything. If export is unavailable, restricted to a proprietary format, or requires the app to remain installed to access your own data, you are betting years of writing on that app's continued existence.
Where Mini Diarium fits
Mini Diarium is a desktop diary app for Windows, macOS, and Linux. It stores entries in a local SQLite database, encrypts each entry with AES-256-GCM before writing to disk, and has no HTTP client. The absence of network code is a structural property, not a setting. The app cannot send your entries anywhere because there is no code to do it.
Exports are available in JSON and Markdown. If you are moving from another tool, Mini Diarium can import journals from Mini Diary, Day One, and jrnl directly.
For the complete overview of how the encryption model works, start with the encrypted journal guide. If you are evaluating Mini Diarium against other apps, the comparison page covers Day One, Notion, Obsidian, Standard Notes, and Joplin on storage model, encryption, and cloud dependency.
For the broader question of what encryption at rest actually means in practice, read what is an encrypted diary. For a direct comparison of local and cloud architectures for journaling, the post on encrypted journal apps vs cloud notes apps covers the structural differences in detail.