FOSS apps: free and open source

Free and open-source software: the source code is public under an open licence.

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jQuarks viewer

LineageOS Jelly browser +adsBlocker +random_UserAgent +offline_.mht +...
- Internet
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid Zapstore
JRBP Survey

Jasper Ridge ant survey navigation and data entry
- Navigation
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
JRPN 16c

Programmer's calculator similar to an HP 16c.
- System & tools
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid
JS-Dict

Japanese-English dictionary app powered by Jisho.org.
- Education
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
J
JSettlers

Remake of "The Settlers 3"
- Games
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub
JSlab

A simple android app for evaluating JavaScript code in a browser context.
- System & tools
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid
jSlide2

A short 3D Platformer with an Online Highscore and viewable Replays.
- Games
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid Zapstore
Json List

previewing JSON from file or url in a user-friendly list format
- System & tools
- FOSS
- Free
- No ads
- No tracking
- Android only
Google Play Aurora Store F-Droid IzzyOnDroid GitHub Zapstore
Just (Video) Player

Simple video player based on ExoPlayer library
- Multimedia
- FOSS
- Free
- No ads
- No tracking
- Android only
Google Play Aurora Store F-Droid GitHub Zapstore Accrescent
Just 24 Hours

A free and open source app that shows a large digital clock
- System & tools
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid
Just Another Workout Timer

A simple timer for your workouts, built with Flutter!
- Health & fitness
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub
Just Delete Me

A directory of direct links to help you delete your account from web services
- Internet
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
just open links in a browser

Sends links to your real browser instead of an app's built-in one
- System & tools
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
JustChess

Chess for one or two players
- Games
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid
Juvavum

Domino Juvavum and Cram are board games which can be played against the computer
- Games
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid
K-19 Player

A music player for OpenSubsonic
- Multimedia
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
k3pler

Network connection blocker and packet analyzer
- Security & privacy
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid
k4android

client for k4ever cash system
- Finance
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid
KabelWacht

A simple, free WireGuard VPN client: scan, import, and manage tunnels.
- System & tools
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
Kachin for AnySoftKeyboard

AnySoftKeyboard Kachin Language pack
- System & tools
- FOSS
- Free
- No ads
- No tracking
- Android only
Google Play Aurora Store F-Droid GitHub Zapstore
Kahon

A fork of Mihon with some annoying restrictions removed
- Internet
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
Kai 9000

OpenClaw alternative in your pocket
- Internet
- FOSS
- Free
- No ads
- No tracking
- Android only
Google Play Aurora Store F-Droid GitHub Zapstore
K
Kaku

Japanese OCR Dictionary
- Education
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub
Kakugo

Learn Japanese with Kakugo
- Education
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid Zapstore
Kakuro

Solve Kakuro puzzles! The addictive blend of Sudoku and crossword sums.
- Games
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
Kandroid (fork)

Manage your projects using Kanboard
- System & tools
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid
Kanji Dojo

Learn & practice writing Japanese characters
- Education
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
Kanji draw

A simple drawn kanji character recognition application
- Education
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid
Karabau

Native Android client for Karakeep to save, organize, and manage bookmarks.
- Productivity
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
Karma Firewall

Karma Firewall blocks apps from accessing the Internet
- Security & privacy
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
Kasette

Offline music player. Import local files, no accounts, no servers.
- Multimedia
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
Katawa Shoujo: Re-Engineered

(18+) A fan-made modernization of the classic visual novel
- Games
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid Zapstore
Kazumi

An anime collection APP based on custom rules.
- Multimedia
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
kboard

Keyboard with customisable one-click responses and powerful automation commands.
- System & tools
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid
KC3ICT Ham Study

Free offline ham radio exam flashcards — Technician, General, and Extra.
- Education
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
KDE Connect

KDE Connect integrates your smartphone and computer
- System & tools
- FOSS
- Free
- No ads
- No tracking
- iOS
- Android
App Store Google Play Aurora Store F-Droid Zapstore
kDI Device Info system permission

androidSpec(s); GSF, Widevine L1/3, microG, Treble, A/B device infos (+otherIDs)
- System & tools
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid
Kechi

Board game for two players
- Games
- FOSS
- Free
- No tracking
- Android only
F-Droid
Keep Alive

Notify others if you haven't used your device in a given period of time
- Security & privacy
- FOSS
- Free
- No ads
- No tracking
- Android only
Google Play Aurora Store F-Droid GitHub Zapstore
Keep Alive Lite

Notify others if you haven't used your device in a given period of time
- Security & privacy
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
Keep it up

Network monitoring
- System & tools
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
Keep Screen On

A screen timeout quick settings tile
- System & tools
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
Keep: FROST Nostr Signer

FROST threshold signer and Nostr event signer for Android
- Security & privacy
- FOSS
- Free
- No ads
- No tracking
- Nostr
- Android only
F-Droid GitHub Zapstore
KeepADB

Keep Wireless Debugging active and toggle it from a tile or widget
- System & tools
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
KeePassDroid

KeePass-compatible password safe
- Security & privacy
- FOSS
- Free
- No ads
- No tracking
- Android only
Google Play Aurora Store F-Droid GitHub Zapstore
KeePassDX Passkey Vault

Manage Passkey / Password in a local and open-source vault
- Security & privacy
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid IzzyOnDroid GitHub Zapstore
KeePassVault

Client app for KeePass databases
- Security & privacy
- FOSS
- Free
- No ads
- No tracking
- Android only
F-Droid GitHub Zapstore
KeepOn - Keep your screen on smartly!

Keep your screen on smartly and easily with Quick Settings.
- System & tools
- FOSS
- Free
- No ads
- No tracking
- Android only
Google Play Aurora Store F-Droid GitHub Zapstore