Interesting and open-source Android apps

F-Droid is an installable catalogue of FOSS (Free and Open Source Software) applications for the Android platform. The client makes it easy to browse, install, and keep track of updates on your device.

Yalp Store lets you download apps from Google Play Store as apk files. It searches for updates of installed apps when it starts and lets you search for other apps. That's it. Yalp saves downloaded apks to your default download folder so you can later open it in your favourite file manager app and tap each one to install the apps.

Aptoide is a distributed marketplace for mobile applications which runs on the Android operating system. In Aptoide, unlike the default Google Play Store, there is not a unique and centralized store but each user manages their own store.

KISS is a blazingly fast launcher for Android requiring nearly no memory to run. Search through your apps, contacts and settings lightning fast. No more time spent trying to find the app you want to launch: enter a few characters of the name and hit enter. Need to call someone? Don't meddle with the call log, just give three letters of their name and push the "phone" button. KISS becomes smarter and smarter as you use it, pushing forward results you're more likely to select.

OpenLauncher is an open source Android launcher project, started from scratch. We aim to create a powerful and community-driven Android launcher.

Privacy is possible, Signal makes it easy. Using Signal, you can communicate instantly while avoiding SMS fees, create groups so that you can chat in real time with all your friends at once, and share media or attachments all with complete privacy. The server never has access to any of your communication and never stores any of your data.

Silence (formerly SMSSecure) is an SMS/MMS application that allows you to protect your privacy while communicating with friends. Using Silence, you can send SMS messages and share media or attachments with complete privacy. It's a fork of Signal.

Wire is a secure and private messenger for phones, tablets and desktop. Crystal clear voice and video calls, private group chats, file sharing, audio and video messages - everything is end-to-end encrypted. Wire works on Android, iOS, Windows, MacOS, Linux and any modern web browser.

Telegram is a messaging app with a focus on speed and security. It’s super-fast, simple, secure and free. Telegram seamlessly syncs across all of your devices and can be used on desktops, tablets and phones alike. You can send an unlimited amount of messages, photos, videos and files of any type (.doc, .zip, .pdf, etc.). Telegram groups have up to 5000 people and you can create channels to broadcast messages to an unlimited number of subscribers.

"It's worth a mention that Telegram's server side is not open-source. However, that doesn't really matter for security purposes, because the end-to-end encryption between client-side end users is tested and works flawlessly in Telegram regardless of the software on the server." — enigmatoid

"It's been shown that Telegram is very insecure and shouldn't be used if security and privacy are your primary concerns, which is something that Telegram has (and still does) advertised as a major feature." — JackDostoevsky

Conversation is a free and open source Jabber/XMPP client for Android 4.0+ smartphones that has been optimized to provide a unique mobile experience. Easy to use, reliable, battery friendly. With built-in support for images, group chats and e2e encryption.

Kontalk is a secure instant messenger, allowing you to send and receive text, image and voice messages (other file types coming soon) to and from other Kontalk users completely free of charge.

Antox is an Android 4+ client for Tox created by Mark Winter. It aims to bring the full multimedia support Tox offers to your device, although it's still currently in heavy development.

Jitsi for Android is an Android port of the Jitsi project: The most feature-rich communicator with support for encrypted audio/video, chat and presence over SIP and XMPP.

Hack.chat is a minimal, distraction-free chat application. Create a chatroom with just a name, there is no preset channel so just enter a chatroom name and a nickname, share the link and communicate.

Riot is a simple and elegant collaboration environment that gathers all of your different conversations and app integrations into one single app.

K-9 Mail is an open-source e-mail client with search, IMAP push email, multi-folder sync, flagging, filing, signatures, bcc-self, PGP, mail on SD & more! K-9 supports IMAP, POP3 and Exchange 2003/2007 (with WebDAV).

ProtonMail is the world’s largest encrypted email service with over 1 million users. The ProtonMail secure email app for Android brings easy-to-use email encryption to your mobile device by seamlessly integrating PGP end-to-end encryption. ProtonMail also provides a modern user interface with a full set of innovative features such as customizable swipe gestures and the ability to send expiring emails.

Tutanota is a free and open source web-mail client that focuses on privacy. All data is stored encrypted and can not be searched, i.e. for commercial usage. It offers dead easy end-to-end encryption.

Lightning is a simple, fast web browser that focuses on design, security, and efficiency. It uses material design, doesn't track you, give you lots of options to protect your privacy, and does it in under 2MB. It gets out of the way of the user.

Firefox Focus is the Mozilla-made browser that considers your privacy first and foremost. By default, it blocks ad-trackers and it helps keep things secure by providing easy ways to clear your browsing history, including passwords and cookies.

Brave has joined forces with LinkBubble to bring you a faster web - by blocking the ads and trackers that get in your way plus all the features you love from LinkBubble. Just go to the settings to turn on or off privacy features like ad blocking, tracker protection and HTTPS Everywhere.

Orbot is a free proxy app that empowers other apps to use the internet more securely. Orbot uses Tor to encrypt your Internet traffic and then hides it by bouncing through a series of computers around the world. Tor is free software and an open network that helps you defend against a form of network surveillance that threatens personal freedom and privacy, confidential business activities and relationships, and state security known as traffic analysis. Orbot creates a truly private mobile internet connection.

Orfox is a new privacy-enhanced browser for Android, based on Mozilla Firefox, configured by default to work with Orbot: Tor for Android. Orfox is built from the same source code as Tor Browser (which is built upon Firefox), but with a few minor modifications to the privacy-enhancing features to make them compatible with Firefox for Android and the Android operating system. Orfox requires Orbot app for Android to connect to the Tor network. In as many ways as possible, we adhere to the design goals of Tor Browser, by supporting as much of their actual code as possible, and extending their work into the additional Android components of Firefox for Android.

Twidere is a powerful X app for Android 4.0+, which gives you a full Material experience and nearly complete (or even better) Twitter feature.

Slide for Reddit is a rock-solid material-designed unofficial browser for Reddit with an easy to use UI and tons of customization. Slide is ad-free, open source, and is packed with many unique features.

RedReader is an unofficial client for the news site Reddit.

NewPipe is a lightweight YouTube front-end for Android. It doesn't need the YouTube-API or any Google Play Services, as NewPipe only parses the YouTube website in order to gain the information it needs.

Open Camera is a fully featured and completely free Camera app for Android phones and tablets.

Tomahawk, the critically acclaimed multi-source music player, is now available on Android. Given the name of an artist, album or song Tomahawk will find the best available source and play it - whether that be from Spotify, Deezer, Google Play Music, SoundCloud, TIDAL, Jamendo or your phone’s local storage. Tomahawk for Android also syncs your history, your loved tracks, artists, albums and your playlists to/from the desktop version of Tomahawk via our new music community, Hatchet. On Hatchet you can hear your friends' favourite tracks and see what they're currently listening to.

AntennaPod is a podcast manager and player that gives you instant access to millions of free and paid podcasts, from independent podcasters to large publishing houses such as the BBC, NPR and CNN. Add, import and export their feeds hassle-free using the iTunes podcast database, gPodder, OPML files or simple RSS URLs. Save effort, battery power and mobile data usage with powerful automation controls for downloading episodes (specify times, intervals and WiFi networks) and deleting episodes (based your favourites and delay settings). But most importantly: Download, stream or queue episodes and enjoy them the way you like with adjustable playback speeds, chapter support and a sleep timer.

Writeily is a minimalist Markdown editor for Android. Simply and elegantly compose notes in markdown or plain text. Organize by folders, save and access files from external storage, and restrict access with a PIN lock.

Omni-Notes is a note-taking open-source application aimed to have both a simple interface but keeping smart behaviour. The project was created by the absence of such applications compatible with old phones and old versions of Android that would propose, however, an attractive look and aligned with the most recent design of the Google operating system.

Simplenote is an easy way to keep notes, lists, ideas, and more. Keep notes on the web, your mobile device, and your computer. Find notes quickly with instant searching and simple tags. Share a list, post some instructions, or publish your thoughts.

Standard Notes is a simple notes app that delivers only the essentials in note-taking. It's fast, syncs your notes on almost every device, supports strong encryption and privacy, gives you 100% data ownership, and supports custom extensions like Markdown and Dropbox Sync.

Mirakel is an easy to use and lightweight To-Do App for your Android Phone or Tablet. Become the most efficient & effective Dev with this task list for the greatest developers in the universe. Get your things done with a strictly organised workflow.

Tasks is a free and open source task management software based on the same code as Astrid.

Nextcloud is a private file sync & share and communication server. It is fully open-source and you can host it yourself or pay a company to do it for you. That way, you are in control of your photos, your calendar and contact data, your documents and everything else.

Syncthing replaces proprietary sync and cloud services with something open, trustworthy and decentralized. Your data is your data alone and you deserve to choose where it is stored, if it is shared with some third party and how it's transmitted over the Internet.

Seafile is an enterprise file hosting platform with high reliability and performance. Put files on your own server. Sync and share files across different devices, or access all the files as a virtual disk.

Wallabag, a self-hostable application for saving web pages. Unlike other services, Wallabag is free (as in freedom) and open source. In order to use this app, you need a hosted Wallabag instance. You can either install Wallabag on your server/webspace or you can register at wallabag.it or framabag.org.

Amaze File Manager is an intuitive, open-source file manager for Android that's both free and ad-free (no upgrade offers, no popups, no ads at all). It's based on Material Design guidelines so it sits very nicely alongside the stock Android experience from Google and being open-source, concerns about privacy and security, should they exist, can easily be addressed.

Ghost Commander is a file manager with two panels for the Android™ platform. Its development was inspired by the famous Midnight Commander, Total Commander and Double Commander desktop applications, so if you are familiar with those great programs, you will find Ghost Commander a familiar and very convenient environment.

Etar Calendar is a material designed calendar based on the ASOP calendar.

DAVdroid is the only all-in-one synchronization solution for your contacts (CardDAV), calendars (CalDAV) and your tasks (based on VTODO). The app is easy to set up and integrates perfectly with your favourite calendar/contacts app (including default apps). It can also be used separately, if you either have CalDAV, CardDAV or only Tasks.

KDE Connect is a project that aims to communicate all your devices. For example, with KDE Connect you can receive your phone notifications on your computer, or just use your phone as a remote control for your desktop. To achieve this, KDE Connect implements a secure communication protocol over the network, and allows any developer to create plugins on top of it. Currently there are KDE Connect clients on KDE, Android and Blackberry, and soon we will support iPhone as well.

Financius - Expense Manager is a simple application that helps you log and track your expenses and keep an eye on your balance.

OsmAnd (OSM Automated Navigation Directions) is a map and navigation application with access to the free, worldwide, and high-quality OpenStreetMap (OSM) data. All map data can be stored on your device's memory card for offline use. Via your device's GPS, OsmAnd offers routing, with optical and voice guidance, for car, bike, and pedestrian. All the main functionalities work both online and offline (no internet needed).

Transportr is the public transport companion that respects your privacy and your freedom. Transportr is a non-profit app developed by people around the world to make using public transport as easy as possible wherever you are. Currently, it works best in Europe, but also supports many places world-wide. If you live in an unsupported area, consider adding it to Transportr. It finds directions from your home, your current position or a given station to wherever you want to go. You can also save entire trips as favourites and find next trips with one click. Discover nearby stations and show upcoming departures including the delays (if there are any).

Android firewall AFWall+ is an advanced iptables editor (GUI) for Android. It provides fine-grained control over which Android apps are allowed to access the network. The original codebase was derived from DroidWall by Rodrigo Rosauro. DroidWall was sold to AVAST in December 2011, and is no longer actively maintained.

AdAway is an ad blocker that uses the hosts file. The hosts file contains a list of mappings between hostnames and IP addresses. When an app requests an ad, that request is directed to 127.0.0.1 which does nothing. There are options to run a web server to respond to blocked hostnames and to direct requests to the IP address of your choosing. You can download hosts files from the app but it is possible to use your own and to add certain sites to the white- and black-lists.