mdwriter

A quiet, private Markdown editor for Android. Open it and write. No accounts, no cloud, no ads, no network access at all: your notes never leave your phone unless you share them.

 

Why this exists

For years the best plain-text writing app on Android was iA Writer. In September 2024 Information Architects stopped developing the Android version after Google cut its Google Drive access and demanded yearly paid security audits, and the app was removed from sale. Existing copies are unsupported and "may become less reliable with newer Android versions". (Press coverage: Thurrott.)

That is the only reason mdwriter exists. I wanted that same calm writing experience on a current Android phone, so I built a small app in its spirit: plain .md files, a typeface made for writing, Markdown you can see but that stays out of the way, and nothing else. If iA Writer ever comes back to Android, use it and support them.

mdwriter is an independent personal project. It is not affiliated with, endorsed by, or connected to Information Architects Inc. "iA Writer" is their trademark. mdwriter uses their open-source iA Writer Duo, Quattro and Mono fonts under the SIL Open Font License (see Credits).

What it does

Library. Swipe right for all your notes. Search, folders, and folders anywhere on your phone.	Preview. Swipe left for a clean rendered page, fully offline.	Formatting pill. Select text for bold, italic, headings, links and more.
Focus mode. Everything but the current sentence or paragraph fades away.	Settings. Theme, typeface, text size, and a few writing options. That is all.

On a tablet or a wide window, the library stays open beside the text, and heading marks hang in the margin:

• Markdown styled as you type. Headings grow, bold gets bold, links and markers turn grey. The text stays plain Markdown you can open anywhere.
• No Save button. Notes save themselves while you write and reopen exactly where you left off.
• Typewriter scrolling keeps the line you are writing in the middle of the screen. Word count is optional.
• Find and replace, task lists you can tick with a tap, and undo/redo.
• Your files, your folders. Keep notes inside the app, or link any folder on the phone (for example Documents/Notes) and edit the files right there.
• Share a note, open .md and .txt files from other apps, and export all notes as a zip.
• Light, dark and pure-black themes, three typefaces (Duo, Quattro, Mono) and six text sizes.

Your notes stay yours

• No permissions. The app asks for nothing: no internet, no storage, no contacts.
• No network. It cannot connect anywhere; the preview is rendered on the phone.
• No accounts, no analytics, no crash reporting.
• Where notes live:
  • Notes in the app's own library are private to the app and are deleted if you uninstall it. Android's own backup may copy them (Google backup only when your backup is encrypted, and phone-to-phone transfer).
  • Notes in a linked folder stay in that folder, like any other file.
• Getting your notes out: Settings > Export all notes… saves every note as a .zip wherever you choose.

Using mdwriter

Gestures

• Swipe right across the text: open the library. Swipe left: open the preview. (You can turn swipes off in Settings.)
• Select text to get the formatting pill.
• Tap a task box - [ ] to tick it.
• The thin grip on the left edge marks the library: tap it, or swipe right anywhere on the page (not from the very edge, that's Android's Back gesture). The ⋮ menu sits top right. Both fade out while you type; tap near the top or scroll up to bring them back.
• Back closes, in order: the keyboard, the selection, the find bar, the library, the preview.

Keyboard shortcuts (with a hardware keyboard; press Meta+/ in the app to see them all)

Shortcut	Action	Shortcut	Action
Ctrl+N	New note	Ctrl+B / Ctrl+I	Bold / Italic
Ctrl+L	Show/hide the library	Ctrl+K	Link
Ctrl+R	Preview	Ctrl+Shift+C	Code
Ctrl+F	Find	Ctrl+Shift+X	Strikethrough
Ctrl+Z / Ctrl+Shift+Z	Undo / Redo	Ctrl+1 … Ctrl+6, Ctrl+0	Heading 1-6, body text

Install on your phone

mdwriter is not on the Play Store. You build it on a Mac and install it on your phone with one command. It runs on Android 16 or 17.

1. One-time setup on the Mac

• Install Android Studio (it brings the Android SDK, adb and a Java runtime). Nothing else is needed; you do not have to put adb on your PATH.
• Check everything: make doctor

2. One-time setup on the phone

1. Enable Developer options: Settings > About phone > tap Build number 7 times, enter your PIN ("You are now a developer!").
2. Open Settings > System > Developer options.

Then pick one way to connect:

USB cable (simplest)

1. In Developer options, turn on USB debugging.
2. Plug the phone into the Mac. On the phone, accept Allow USB debugging?; tick Always allow from this computer.

Wi-Fi (no cable; phone and Mac on the same Wi-Fi network)

1. In Developer options, tap Wireless debugging, turn it on, and allow it on this network.
2. Tap Pair device with pairing code. The phone shows a 6-digit code and an IP address & port.
3. On the Mac: make pair HOST=192.168.1.23:37123 CODE=123456 (use the values from the phone).
4. The phone normally connects by itself a few seconds later (make devices shows it). If it does not: make connect HOST=<IP address & port shown on the main Wireless debugging screen> (this port is different from the pairing port). Pairing is remembered; next time just turn Wireless debugging on.

3. Install

make install        # builds, installs (or updates) and opens mdwriter; your notes are kept

Several phones or an emulator connected? make install DEVICE=<serial> (see make devices). You can turn Developer options off again afterwards; the app keeps working.

4. Back up your signing key (important)

The first make install creates ~/.config/mdwriter/release.jks and ~/.config/mdwriter/keystore.properties. Every future update must be signed with this key. Copy the whole ~/.config/mdwriter/ folder to your password manager or an encrypted backup (make keystore-info shows where the files are and their fingerprint). On a new Mac, put them back before running make install. Without the key you cannot update the app without uninstalling it, and uninstalling deletes the notes stored inside the app.

Updating

git pull && make install. Your notes are kept: every build has a higher version number, so it is an in-place update. Never uninstall the app to "reinstall" it.

Troubleshooting

Message	Meaning / fix
no Android device connected	USB: cable/port, USB debugging on, accept the prompt. Wi-Fi: Wireless debugging on, same network, make pair again.
device unauthorized	Unlock the phone and accept Allow USB debugging?. No prompt? Developer options > Revoke USB debugging authorizations, unplug, replug.
2 devices connected - choose one	make install DEVICE=<serial> (serials from make devices).
needs Android 16 (API 36) or newer / INSTALL_FAILED_OLDER_SDK	The phone runs Android 15 or older; mdwriter supports Android 16 and 17 only.
INSTALL_FAILED_UPDATE_INCOMPATIBLE (signed with a DIFFERENT key)	The app on the phone was signed with another key (new Mac, lost ~/.config/mdwriter). Nothing was changed on the phone. Restore your backed-up key files and run make install again. Only if the key is truly lost: export your notes first, then make uninstall CONFIRM=yes && make install (uninstalling deletes the notes inside the app).
INSTALL_FAILED_VERSION_DOWNGRADE	The phone has a newer build (Mac clock wrong?). make install VERSION_CODE=<bigger number>.
INSTALL_FAILED_USER_RESTRICTED	Accept the prompt on the phone; on Xiaomi/Oppo/Vivo also enable Developer options > Install via USB.
Samsung: USB commands ignored	Settings > Security and privacy > Auto Blocker blocks USB commands; turn it off while installing.
offline device	Unplug/replug, or restart adb: ~/Library/Android/sdk/platform-tools/adb kill-server.
no JDK 17-26 found	Install Android Studio, or brew install openjdk@21. Gradle cannot run on Java 27.
Something else breaks	Run make logcat while reproducing it and keep the output; make doctor checks the Mac side.

Known limitations

• Very long notes (hundreds of pages) are slower: typing in a 100,000-character note is noticeably less snappy, and opening a 300,000-character note takes a few seconds.
• Right-to-left text (Arabic, Hebrew) works, but on wide screens those paragraphs are offset by the heading margin.
• Notes over 5 MB open read-only; files over 16 MB and non-text files are refused.
• It has been tested on the Android emulator. Some things (TalkBack, very large font sizes, split screen, right-to-left layouts, three-button navigation) have not yet been checked on a real phone.

Credits

• Fonts: iA Writer Duo, Quattro and Mono by Information Architects Inc., based on IBM Plex, under the SIL Open Font License 1.1. The full licence texts are in app/src/main/assets/licenses/ and in the app under Settings > About.
• Markdown parsing for the preview: commonmark-java and autolink-java.

For developers

Command	What it does
make help	List all targets.
make doctor	Check JDK, SDK, signing key and connected devices.
make emulator	Boot the default AVD (Pixel_10_Pro_XL) and wait until ready.
make devices	List connected devices with their Android version.
make install-debug DEVICE=<serial>	Build + install + launch the debug app (me.gcg.mdwriter.debug, a separate app with its own notes).
make run / make run-debug	Launch the installed release / debug app (no build).
make test	Run all JVM unit tests.
make test-device DEVICE=<serial>	Run instrumented tests on a device or emulator.
make lint / make format	Android Lint / auto-format (Spotless + ktlint).
make check	What CI runs: format check, lint, unit tests, release build (R8).
make logcat	Stream the app's logs (release + debug).
make keystore-info	Show where the release signing key is and its fingerprint.
make backup-notes	Copy the debug app's notes to ./notes-backup-<time>/ (the release app's notes can't be read over adb; use Export).
make uninstall CONFIRM=yes	Uninstall the release app. Deletes every note stored inside it.

Requirements: Android Studio (brings the SDK + a JDK). For raw Gradle calls: export JAVA_HOME=$(/usr/libexec/java_home -v 21) (Gradle 9 cannot run on JDK 27).

Project layout: app/ is the Android app (Compose UI, a View-based editor engine, storage, settings); core/markdown/ is a pure Kotlin Markdown engine; plans/ holds the implementation plan, QA matrix and performance results; docs/screenshots/ holds the images above (taken on the Android emulator).