What Are Snap, Flatpak, and AppImage Packages?

Snap, Flatpak, and AppImage are universal Linux package formats that bundle an application with its dependencies, allowing the same package to run on any Linux distribution. Snap packages (from Canonical) are installed with snap install appname and run in a sandboxed environment. Flatpak packages are installed with flatpak install flathub appname and are commonly used for desktop applications. AppImages are self-contained executable files that run without installation — just download and run. All three solve the “works on my distro” problem but each takes a different approach.

The Cross-Distribution Software Problem

Linux’s greatest strength — its diversity of distributions — has historically been one of its biggest software distribution headaches. A developer writing a Linux application faces a fragmented ecosystem: Ubuntu uses .deb packages, Fedora uses .rpm packages, Arch Linux uses its own format. Each distribution has different library versions, different default configurations, and different packaging policies. To officially support their software on Linux, developers historically needed to maintain separate packages for dozens of distributions, each with different dependencies, versioning, and update schedules.

This fragmentation made it genuinely difficult to distribute software on Linux. Commercial applications like Spotify, Slack, or Discord found it impractical to package for every distribution. Independent developers releasing a small tool faced a packaging burden that discouraged Linux support entirely. Even within a distribution, version mismatches between what a developer tested against and what a user had installed caused the dreaded “works on my machine” failures.

Three solutions emerged to solve this problem by taking fundamentally different approaches: Snap, Flatpak, and AppImage. All three share a core insight: bundle the application with its dependencies so it runs consistently regardless of what the host system has installed. But they differ significantly in how they implement this idea, who controls the ecosystem, how they handle security, and the tradeoffs they make.

This article explains each format thoroughly — how it works technically, its practical strengths and weaknesses, when it is the right choice, and how to use it — along with a clear comparison to help you understand why Linux now offers three different answers to the same problem.

The Core Problem: Why Universal Packages Exist

To appreciate what Snap, Flatpak, and AppImage solve, consider what happens without them.

Traditional Package Management: Tightly Coupled

When Firefox is packaged for Ubuntu, the package specifies: “I require libstdc++ version X.Y.Z, libgtk version A.B.C, and several other library versions.” The Ubuntu package maintainer tests Firefox against the specific library versions in Ubuntu 24.04’s repositories and packages it accordingly.

This works well when:

• The distribution’s library versions match what Firefox was tested against
• You are using the supported distribution version
• The developer actively maintains packages for your distribution

It breaks when:

• You need a newer version of the software than your distribution packages
• The developer does not officially support your distribution
• Library updates in your distribution break compatibility
• The software requires a newer library than your distribution provides

These failures are common enough that universal packages have found a substantial place in the Linux ecosystem — not replacing traditional packages but complementing them for cases where distribution-specific packaging falls short.

The Bundle Approach

All three universal formats solve this by bundling: the application comes with its own copies of the libraries and dependencies it needs. Instead of relying on finding the right versions in the system, the application brings what it needs.

Traditional package:     App binary + "please install libX v2.3"
Universal package:       App binary + libX v2.3 (bundled) + libY v1.8 (bundled) + ...

The tradeoff: larger download and disk usage, since every application carries its own copy of common libraries rather than sharing system libraries.

Snap: Canonical’s Universal Package System

What Snap Is

Snap is a package format and ecosystem created by Canonical (the company behind Ubuntu). A snap is a compressed, read-only filesystem image containing an application and all its dependencies, along with metadata defining how the application should be run and what resources it can access.

The Snap ecosystem is centralized: the Snap Store (snapcraft.io) is the sole official source for snaps. Canonical controls the infrastructure and has final say over what appears in the store.

How Snap Works Technically

When you install a snap:

1. The snap file (a .snap file, which is a SquashFS filesystem image) is downloaded from the Snap Store
2. It is stored in /var/lib/snapd/snaps/
3. The snap is mounted as a read-only loop device in /snap/appname/revision/
4. A launch script in /snap/bin/ makes the application runnable by name

Each snap runs in a confined environment managed by AppArmor and seccomp profiles. The application can only access resources explicitly permitted by its declared interfaces — this is the confinement model.

$ ls /snap/firefox/
current  3770  3785

$ ls /snap/firefox/current/
bin  etc  lib  meta  snap  usr  ...

$ mount | grep snap | head -5
/var/lib/snapd/snaps/firefox_3785.snap on /snap/firefox/3785 type squashfs (ro,nodev,relatime)
/var/lib/snapd/snaps/core22_1380.snap on /snap/core22/1380 type squashfs (ro,nodev,relatime)

The snapd Daemon

Snap requires the snapd background service running at all times. snapd handles:

• Installing, updating, and removing snaps
• Managing confinement and security policies
• Automatic background updates (snaps update silently without user intervention by default)
• Managing snap connections and interfaces

$ systemctl status snapd
● snapd.service - Snap Daemon
     Loaded: loaded (/lib/systemd/system/snapd.service; enabled)
     Active: active (running)

Installing Snaps

$ snap find firefox            # Search for a snap
$ sudo snap install firefox    # Install a snap
$ sudo snap install vlc        # Install VLC media player
$ sudo snap install code --classic    # Install VS Code (classic confinement)

The --classic flag for some snaps disables confinement, giving the application the same access as a regular system application. VS Code, many developer tools, and command-line utilities often require classic confinement.

$ snap list                    # List installed snaps
Name       Version          Rev    Tracking       Publisher   Notes
core22     20240111         1380   latest/stable  canonical   base
firefox    122.0.1          3785   latest/stable  mozilla     -
vlc        3.0.20           3650   latest/stable  videolan    -
code       1.86.0           158    latest/stable  vscode      classic

Updating Snaps

Snaps update automatically in the background, typically 4 times per day. To update manually:

$ sudo snap refresh              # Update all snaps
$ sudo snap refresh firefox      # Update a specific snap
$ snap refresh --list            # List available updates without installing

To control automatic updates (Snap does not easily support disabling them entirely — this is a commonly criticized limitation):

$ sudo snap set system refresh.timer=fri,23:00-01:00    # Update only Friday nights
$ sudo snap set system refresh.hold=72h                  # Delay updates by 72 hours

Removing Snaps

$ sudo snap remove firefox
$ sudo snap remove --purge firefox    # Remove including saved state/data

Snap’s Controversial Aspects

Snap has attracted criticism on several points:

Centralized control: All snaps must go through Canonical’s Snap Store. There is no official way to run an alternative snap store (unlike Flatpak, which supports multiple repositories). This makes some users uncomfortable with dependency on a single commercial entity.

Performance: Snaps can start noticeably slower than traditional packages because the SquashFS image must be decompressed and mounted. Firefox as a snap launches several seconds slower than Firefox as a .deb on some systems.

snapd always running: The snap daemon must run continuously, consuming RAM and CPU even when no snaps are being used.

Forced automatic updates: Unlike traditional packages where you control when updates happen, snaps update on their own schedule by default.

Privacy concerns: The Snap Store communicates with Canonical’s servers to check for and download updates, raising some users’ privacy concerns.

Ubuntu’s preferential treatment: Ubuntu installs certain applications (Firefox, Thunderbird, various others) as snaps by default without clearly communicating this to users, which has caused frustration when users expected traditional .deb behavior.

Despite these criticisms, the Snap Store contains a large selection of software, and snaps work reliably for many use cases.

Flatpak: The Community-Oriented Universal Package

What Flatpak Is

Flatpak is a universal packaging system created by Alexander Larsson at Red Hat and developed as a community project. Like Snap, Flatpak bundles applications with their runtimes and provides a sandboxed execution environment. Unlike Snap, Flatpak is designed around decentralization — anyone can set up a Flatpak repository, and users can install from multiple repositories simultaneously.

The dominant Flatpak repository is Flathub (flathub.org), a community-run store with over 2,000 applications. But enterprise organizations, individual developers, and distributions can run their own Flatpak repositories.

How Flatpak Works Technically

Flatpak uses a different architectural approach from Snap:

Runtimes — Flatpak applications do not bundle every library independently. Instead, they share runtimes — curated sets of common libraries. Common runtimes include:

• org.freedesktop.Platform — basic Freedesktop libraries
• org.gnome.Platform — GNOME libraries and toolkit
• org.kde.Platform — KDE/Qt libraries

An application specifying it needs org.gnome.Platform 46 downloads that runtime once and shares it with all other GNOME applications. This dramatically reduces disk usage compared to every application bundling everything independently.

$ flatpak list --runtime
Name                              Application ID              Branch
GNOME Application Platform...    org.gnome.Platform          46
KDE Application Platform          org.kde.Platform            6.6
Freedesktop Platform              org.freedesktop.Platform    23.08

Sandboxing — Flatpak uses kernel namespaces, seccomp, and bubblewrap to create isolated execution environments. The sandbox restricts file system access, network access, and hardware access. Users grant permissions through portals — controlled interfaces that allow sandboxed apps to access resources in a user-controlled way (file picker portal, screenshot portal, etc.).

Application storage:

/var/lib/flatpak/          ← System-wide installations
~/.local/share/flatpak/    ← Per-user installations

Setting Up Flatpak and Flathub

On Ubuntu (Flatpak is not installed by default):

$ sudo apt install flatpak
$ sudo apt install gnome-software-plugin-flatpak    # For GUI integration
$ flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo

Restart required after adding Flathub (or log out and back in).

On Fedora (Flatpak is pre-installed but Flathub needs enabling):

$ flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo

Installing Flatpak Applications

$ flatpak search firefox            # Search Flathub
$ flatpak install flathub org.mozilla.firefox    # Install by application ID
$ flatpak install flathub com.spotify.Client     # Install Spotify
$ flatpak install flathub com.discordapp.Discord # Install Discord
$ flatpak install flathub org.libreoffice.LibreOffice  # Install LibreOffice

Application IDs are in reverse domain name notation (like Android apps), ensuring uniqueness across repositories.

Running a Flatpak application:

$ flatpak run org.mozilla.firefox

Or use the application launcher — installed Flatpaks appear in the application menu automatically.

Updating Flatpaks

$ flatpak update                    # Update all flatpaks
$ flatpak update org.mozilla.firefox  # Update specific app

Unlike Snap, Flatpak does not automatically update in the background by default. Updates happen when you explicitly run flatpak update or when your software center updates them.

Removing Flatpaks

$ flatpak uninstall org.mozilla.firefox
$ flatpak uninstall --unused    # Remove unused runtimes (frees significant space)

Managing Flatpak Permissions

Flatpak’s permission system is more transparent and user-controllable than Snap’s:

$ flatpak info --show-permissions org.mozilla.firefox

The Flatseal application provides a graphical interface for managing Flatpak permissions:

$ flatpak install flathub com.github.tchx84.Flatseal

Flatseal lets you see and modify what each Flatpak application can access — filesystem locations, network, devices, hardware, and more.

AppImage: The Zero-Installation Approach

What AppImage Is

AppImage takes a fundamentally different philosophy from Snap and Flatpak. There is no package manager to install, no daemon to run, no store to register with. An AppImage is a single, self-contained executable file that runs on any Linux distribution without any installation.

An AppImage is a SquashFS filesystem image (like a Snap) that contains the application and all its dependencies. When you “run” the AppImage, it mounts itself as a temporary loop device, executes the application from within that mount, and unmounts when the application exits.

The AppImage Workflow

1. Download appname.AppImage from the developer's website
2. Make it executable: chmod +x appname.AppImage
3. Run it: ./appname.AppImage

That is the entire process. No package manager. No root access. No system modification. No installation in any traditional sense.

$ wget https://example.com/myapp-1.5.0-x86_64.AppImage
$ chmod +x myapp-1.5.0-x86_64.AppImage
$ ./myapp-1.5.0-x86_64.AppImage

AppImage Features

Optional desktop integration: AppImages can optionally integrate with the desktop — creating a .desktop launcher in the application menu and an entry in the system tray — if the user approves when first run. This integration is opt-in and reversible.

$ ./myapp.AppImage --appimage-extract-and-run    # Run without FUSE mounting
$ ./myapp.AppImage --appimage-help               # Show AppImage-specific options

FUSE dependency: AppImages typically require FUSE (Filesystem in Userspace) to mount themselves. Most desktop Linux systems have FUSE available. If not:

$ sudo apt install fuse libfuse2    # Ubuntu/Debian
$ sudo dnf install fuse fuse-libs   # Fedora

Updating AppImages

AppImages have no built-in update mechanism — you download a new version and replace the old file. Some AppImages include the appimageupdatetool capability for delta updates, but this is not universal.

The AppImageLauncher tool provides better desktop integration and update management:

$ sudo apt install appimagelauncher    # If available, or download from GitHub

AppImageLauncher intercepts AppImage launches, offers to integrate them with the desktop, and provides basic update checking for supported apps.

No Sandboxing in AppImages

Unlike Snap and Flatpak, AppImages have no security sandboxing. An AppImage runs with your full user permissions — it can read your files, connect to the internet, and do anything you can do. This is the same trust level you give any downloaded application.

This is not inherently dangerous — you trust the developer of any software you run — but it is different from the sandboxed model of Snap and Flatpak, where applications are restricted to explicitly declared permissions.

Where to Find AppImages

• AppImageHub (appimage.github.io) — a community catalog
• Developer websites — many projects (Kdenlive, Krita, GIMP, various developer tools) offer AppImage downloads alongside other formats
• GitHub releases — many open source projects post AppImages in their GitHub releases

Comparison: Snap vs. Flatpak vs. AppImage

When to Use Each Format

Choose Snap When:

• The software you want is only available as a Snap (check snapcraft.io)
• You are on Ubuntu and it is the pre-installed format for an application
• You want automatic background updates without thinking about them
• You are installing developer tools like VS Code, kubectl, or AWS CLI that use classic confinement

Choose Flatpak When:

• You want the best sandboxed desktop application experience
• You want transparency and user control over application permissions (via Flatseal)
• You care about not being dependent on a single company’s infrastructure
• You want shared runtimes to reduce disk usage
• The application is available on Flathub (most major desktop apps are)

Flatpak is generally the recommended choice for desktop applications — it has better security transparency, community governance, shared runtimes, and user-controlled permissions.

Choose AppImage When:

• You want to try an application without installing anything
• You need to run software on a locked-down system where you cannot install packages
• You want the simplest possible workflow: download, chmod, run
• The developer only offers an AppImage
• You want a portable application to carry on a USB drive

Prefer Native Packages When:

• The application is available in your distribution’s official repositories
• You want the best system integration, smallest size, and fastest startup
• Security updates are important (native packages update with your system)

For most well-maintained applications, native packages from your distribution’s repositories remain the first choice. Universal packages shine when native packages are unavailable, outdated, or when you need a newer version than your distribution provides.

Practical: Installing Firefox Three Ways

The same application illustrates the differences clearly:

As a native .deb (Ubuntu):

$ sudo apt install firefox    # Or on Ubuntu: may install as Snap by default
# ~100 MB, shares system libraries, starts fastest

As a Snap:

$ sudo snap install firefox
# ~250 MB, sandboxed, automatic updates, slower startup

As a Flatpak:

$ flatpak install flathub org.mozilla.firefox
# ~200 MB + shared runtime, sandboxed, user permission control

As an AppImage:

# Download from mozilla.org (they offer Firefox as AppImage)
$ chmod +x firefox-*.AppImage
$ ./firefox-*.AppImage
# ~90 MB compressed, no installation, no sandbox

Each method installs the same Firefox browser but with different tradeoffs in disk usage, startup speed, update behavior, sandboxing, and integration.

Managing All Three: AppImageLauncher and Similar Tools

AppImageLauncher provides better desktop integration for AppImages — automatically placing them in the application menu and managing updates:

# Available from GitHub: https://github.com/TheAssassin/AppImageLauncher
$ sudo apt install appimagelauncher    # If available in your distribution's repo

Gear Lever — another AppImage manager with a graphical interface for integrating AppImages into the desktop:

$ flatpak install flathub it.mijorus.gearlever

GNOME Software and KDE Discover both support Flatpak natively on most distributions, providing a graphical interface for browsing, installing, updating, and removing Flatpak applications without using the command line.

Quick Reference: Commands for Each Format

Snap

Flatpak

AppImage

Conclusion: Three Solutions to One Problem

Snap, Flatpak, and AppImage each represent a different answer to the same question: how do you distribute software to Linux users across hundreds of different distributions without the traditional distribution-specific packaging burden?

Snap’s answer is centralized infrastructure with automatic management and sandboxing, controlled by Canonical. Flatpak’s answer is decentralized repositories with shared runtimes and community governance, with transparent user-controlled sandboxing. AppImage’s answer is radical simplicity: a single file that just works anywhere without any infrastructure at all.

None of these formats has “won” — all three coexist because each serves different needs well. Understanding what each is and how it works lets you make informed choices: reaching for Flatpak when you want the best sandboxed desktop experience, Snap when a specific application is available there and not elsewhere, and AppImage when you want maximum portability and simplicity.

The existence of these three formats alongside traditional .deb and .rpm packages reflects Linux’s diversity and the community’s willingness to try different approaches rather than forcing everyone into one solution. That diversity, occasionally confusing to newcomers, ultimately serves users by ensuring that whatever software you need, there is a way to run it on Linux.