Android is the most popular operating system for mobile phones and tablets.


Most vendors have their own (slightly modified) distribution of Android.
Some distributions do not allow the user to remove preinstalled apps.
Luckily, there are devices available that support flashing alternative Android distributions.

Successor of CyanogenMod
Supported devices:

As in 2020, there are approximately three million apps on Google Play.
If you need an app for something, you are possibly trying out some of them.
Some of them need access to personal data. Some of them are full of advertisements.
Here is a list of apps, I can recommend.

App Stores

App store with free and open source software (foss)
Aurora Store
Download apps from Google Play without Google Apps (GApps) installed


Internet browser based on Firefox
K-9 Mail
Full-featured email client
Lightweight YouTube front-end
Change Detection
Automatically detects changes on websites


Open Camera
Feature-rich camera app
Barcode Scanner
QR code scanner


Offline/online maps and navigation
City navigation


Etar - OpenSource Calendar
Supports offline calendars
Calendar Import-Export
Import & export (backup) calendars using ics files


Export Contacts
Backup contacts in vCard 3.0 contacts file (*.vcf)
Share my number via QR code
This app displays a QR code others can easily scan


Document Viewer
Successor of EBookDroid
LibreOffice Viewer
Read various office file formats


Live wallpaper of famous art


Apple Flinger
Use a slingshot to shoot with apples
A factory-based sandbox tower defense game
PSP emulator

Science and Education

Graph 89
Calculator emulator


Text editor with syntax highlighting
Terminal emulation
On first start, the bootstrap zip file is downloaded and extracted to /data/data/com.termux/files/usr/.
Terminal toolbar can be hidden by pressing volume up and q.
Command line access to device API
Version 0.31 is the last that supports sending sms messages.
To install old versions, the F-Droid Archive repository needs to be enabled.
Hacker's Keyboard
Keyboard with tab, ctrl and arrow keys

Verify Signature of Packages

Android packages (APKs) are signed with self-signed certificates.

The command line tool apksigner is part of the Android SDK Build Tools:

In Termux, apksigner can be installed using the following command:

pkg install apksigner

To verify the signature of an APK, execute the following command:

apksigner verify --print-certs org.fdroid.fdroid_1010000.apk
Signer #1 certificate DN: CN=Ciaran Gultnieks, OU=Unknown, O=Unknown, L=Wetherby, ST=Unknown, C=UK
Signer #1 certificate SHA-256 digest: 43238d512c1e5eb2d6569f4a3afbf5523418b82e0a3ed1552770abb9a9c9ccab
Signer #1 certificate SHA-1 digest: 05f2e65928088981b317fc9a6dbfe04b0fa13b4e
Signer #1 certificate MD5 digest: 17c55c628056e193e95644e989792786
Signer #1 certificate DN: CN=CodeSigning for HERE Global BV, OU=Android Signing, OU=Android Signing, O=HERE Global BV, L=Veldhoven, ST=Veldhoven, C=NL
Signer #1 certificate SHA-256 digest: f3fa1a6eb3f8bace3662e83ab167a90462d1a78240e64cf24675887c5d78cb13
Signer #1 certificate SHA-1 digest: 6d256640c0eff26ccb3a8b817cdc901f3d1d77b4
Signer #1 certificate MD5 digest: 528eab01b512151498f89f5e88767bf9
Magic Earth
Signer #1 certificate DN: CN=ROUTE 66, OU=ROUTE 66 Switzerland GmbH, O=ROUTE 66 Switzerland GmbH, L=Brasov, ST=Romania, C=RO
Signer #1 certificate SHA-256 digest: fa91bd3a8bfa2b03bda48422b238d584f23921154a5279e721f2f90a74d38806
Signer #1 certificate SHA-1 digest: 3705ba93d86f9566cdb440977e65c8df660514ae
Signer #1 certificate MD5 digest: 82380142088327f4d4a14c9547ff46de
Tor Browser
Signer #1 certificate DN: C=US, ST=WA, L=Seattle, O=The Tor Project, CN=Tor Browser
Signer #1 certificate SHA-256 digest: 20061f045e737c67375c17794cfedb436a03cec6bacb7cb9f96642205ca2cec8
Signer #1 certificate SHA-1 digest: 6e9d890dcf0d5ca0d7c8f28c822ed228da5f3490
Signer #1 certificate MD5 digest: e8ee59c262de3d867b015afbae38e061

Send SMS Messages

Using Termux:API

termux-sms-send -n "+1234567890" "Just a test!"

Using ADB

adb shell service call isms 7 i32 0 s16 "" s16 "+1234567890" s16 "null" s16 "Just a test!" s16 "null" s16 "null"

Android Studio

The Android Studio is the official Integrated Development Environment (IDE)
for Android. The IDE based on IntelliJ IDEA.
The installer is available on the developer pages of Android:

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Dominik Schürmann