What are the best cross-platform FLOSS messengers?

VoIP:Yes

Signal is free and open source software, enabling anyone to verify its security by auditing the code. It's the only private messenger that uses open source, peer-reviewed cryptographic protocols to keep your messages safe. See More

Top Pro

Free and open source

Top Con

Needs access to your phone number and contacts to work

Peter J. Mello's Experience

So few of us have the deep knowledge of cryptography necessary to gauge when our communications are secure, we have no choice but to select the best such arbiters we can. Signal is the consensus pick of the Electronic Frontier Foundation and Edward Snowden, among others, and so this is where I hang my hat. See More

Top Pro

Recommended by Edward Snowden

Edward Snowden uses this messenger and recommends it to everyone who is concerned about his privacy. See More

Top Con

Unreliable notifications

Sometimes messages won't be received if the Signal app has been closed for a long time or hasn't been opened after booting the device. See More

Top Pro

Supports encrypted group chats

Top Con

Single device

You cannot send and receive messages from multiple devices, but there is a desktop extension. See More

Top Pro

SMS/MMS support

Signal can be your default SMS/MMS text messenger. Encryption is not possible when sending SMS to your contacts, however. See More

Top Con

Closed-source server software

Without the ability to audit server code, user security may be trivially compromised. See More

Top Pro

Supports sharing of various different media types

Signal supports: emoji, pictures, videos, audio, contacts, any location and GIF. See More

Top Con

Uses message mirroring

You phone must be on and connected to the internet for Signal Desktop to work. See More

Top Pro

Message mirroring on Signal Desktop

Signal Desktop is a Chrome extension that allows you to mirror messages from your phone, including replying. See More

Top Con

If SMS/MMS imported, other apps can't read SMS

For those using Join, Pushbullet, or similar apps to send and receive SMS/MMS from web or desktop, putting your SMS in Signal somehow breaks this functionally. The dev is aware but plans to remedy the situation have not been named a priority See More

Top Pro

You can easily view all media exchanged

You can easily view all media shared in the chat without scrolling back to when it was shared. See More

Top Pro

Note-to-Self feature

Allows you to send messages to yourself and sync to desktop so you can use Signal as a kind of encrypted Pushbullet alternative. See More

Works on Windows, Mac, Linux, Android iOS, Windows Phone, and Firefox OS even. Has a web app that changes it's appearance based on the device it's running on and if it's browser is full screen, etc. See More

Telegram

Top Pro

Cross-platform

Top Con

Not fully open source

Telegram has an open API and protocol free for everyone, but the backend software is not open source. Therefore 100% privacy can not be evaluated. See More

Rebel's Experience

The best messenger there is period. Iv'e used this since the beginning and its better than Messenger, Whatsapp, iMessage, etc. It's so good even Whatsapp started "borrowing" their features. See More

Specs

Platforms:Web, Android, iOS, Windows, Linux, macOS, BSD, Windows phone, UWP

Media:images / video / audio / GIFs / stickers / PiP Video / Videomessages

Message history:Yes

End-to-end encryption:Secret chats

Copy/paste videos, gifs, images, geolocation, and documents, drag over files for practically any time up to 1.5GB in size. Images can be compressed, too. See More

Top Pro

Free and convenient large file sharing

Top Con

Only "Secret Chat" messages are encrypted end to end

The only way to get end-to-end encryption (client-client) using Telegram is to use the Secret Chat function, anything through the service is server-client encrypted. Moreover, secret chats are only implemented in some clients (Mobile apps, Native MacOs, Native Win10). Other clients as Webogram (Web) or TDesktop (platform independent) do not offer secret chats, which makes it impossible to use Secret chats on older veersions of Windows, Linux, BSD or TVs. See More

Rafael Social User's Experience

Always is the first in bring user new functionalities. It's ability to work simultaneously in distinct platforms and environments make it a productive tool, flexible and always working. See More

Top Pro

Save time with inline bots and link previews

Unfortunately, on the desktop videos don't apply, but images are viewable without visiting popular websites like imgur and Instagram. You can play YouTube videos and others within the app, so you don't need to embed code or anything. With inline bots, such as @gif, @pic/bing, @vid/YouTube, etc, you can look things up without leaving the client or chat that you're in. Simply type the name and some keywords and wait for the results to load. See More

Top Con

Registered as an LLC in the US

Subject to subpoenas and gag orders via the US government. However, Telegram has a history of publicly denouncing such requests and will not comply. The company is also registered in many other jurisdictions to avoid such threats. See More

TrustworthyBorlung's Experience

Free - Nonsense, server is not free. Black box solution. See More

Top Pro

Media messaging

Videos, gifs, images, geolocation, and documents. See More

Top Con

Stores chats

Chats are stored on Telegram's servers. See More

cosmo's Experience

Broken encryption and a lack of features left me wanting more and ultimately looking elsewhere. See More

Top Pro

Beautiful UI

Very customizable with a lot of clean looking options. See More

Top Con

Can only be used with a phone number

It is not possible to activate and use Telegram by mail etc. You need a phone number. See More

PerfectSimargl's Experience

easy gui,crossplattform. getting very popular See More

Top Pro

Compelling Story

The founder Pavel Durov was exiled from Russia after refusing to cooperate with the Kreml to stamp the opposition and oppress the people. He nearly lost everything he worked on and started Telegram in exile. He has been a big proponent of free speech and unquestioned privacy since then. https://www.bloomberg.com/news/articles/2017-12-12/cryptic-russian-crusader-says-his-5-billion-app-can-t-be-bought See More

Top Con

Not really secure

The encryption it uses is flawed and just not very good in general. However, Telegram claims to fix those issues with its homegrown protocol MTProto. See More

Top Pro

Supergroups of up to 100,000 people

In Supergroups, anyone along with admins can delete their messages from all sides. A message can be pinned to the top. All of the user's messages can be deleted by an administrator, and they can be banned and reported as well. Supergroups can have a public link (outside of Asia, due to high spam volumes), which is also a username. See More

Top Con

"Secret Chat" feature is not available for desktop client

Secret chats with end to end encryption are only available on mobile apps. See More

Top Pro

Desktop app handles HIDPI

The desktop app has a built in setting to scale the UI of the app up to 200% which allows for those with 4k monitors/screens to use the app without scaling issues. See More

Top Con

Easy to crack by Intelligence services when used without 2FA

Without 2FA (Two Factor authentification) enabled government services only need to intercept one login SMS to get near full access to the account. See More

Top Pro

In Cyberwar with authoritärian Regimes

Telegram refuses to cooperate with any law enforcement and as a result, was blocked in Russia and Iran. Telegram evaded the ban by using many proxy servers and Russia only managed to cripple its own Internet completely. Telegram worked fine. See More

Top Con

Default client does not visually separate Chat, Groups and so on

All chats, bots, groups, supergroups, and channels are shown under the same panel. There are clients with better-organized interfaces, like PlusMessenger (Android Telegram client), for example. Those show each category in their own panel. See More

Top Pro

Free of cost

The application is available free of cost. See More

Top Con

Does not support spherical 360° photos

Spherical 360° photos becoming more popular these days, but Telegram does not support such format. See More

Top Pro

Privacy focused

In addition to the end-to-end encryption that provides privacy to communications, the app also includes self destructing timers for chats, and the ability to permanently delete messages, yours and theirs, from your device. See More

Top Pro

Customer support is within the app

Although it's volunteer based, but still pretty top-notch if available, which it tends to be. See More

Top Pro

Possible to send photos and videos without compression

Top Pro

User can choose custom clients

As an open source application, anyone can develop their own clients, such as PlusMessenger (Android), Franz (Linux, Windows) and many others. See More

Top Pro

2-step verification

You can set up an additional password to your account, which can be reset by your email. You don't have to use an email, if you do not want to. If you lose access to your email or forget your password, you will be able to reset it via text message if your account is over seven days old and will receive it within a week (in case you recover anything before then). See More

Top Pro

Saved messages

You can write messages to yourself. You can write some notes, add links, and see everything across all your devices. See More

Top Pro

High quality calls

Uses the latest GPL audio codecs, such as Opus, an adaptative high-quality codec that supersedes AAC at any bitrate. See More

Top Pro

Channels for one way broadcasting

Broadcasting channels suitable for announcing things. See More

Top Pro

Multiplatform native client apps

There are native desktop, mobile and web client apps, that are optimized for speed and are light on memory usage. See More

Top Pro

Unlimited cloud space

Every user can upload as much as they want. The limit for one File is 1.5GB See More

Top Pro

Whatsapp copies nearly all features from Telegram

Whatsapp, being the biggest messenger, is far behind in innovation and feels the need to copy nearly all features from Telegram. Therefore, Whatsapp's new features are usually available in Telegram at least six months in advance. The only exceptions from this are starres messages and photo albums. See More

Top Pro

Cloud chat keys are kept in different jurisdiction

Even though encryption used for cloud-based storage (e.g. Gmail, Facebook, iCloud) may not be as secure as end-to-end encryption or zero-knowledge storage, Telegram does the most that it can by holding keys to chats in different jurisdictions, requiring intergovernmental cooperation to obtain the keys. This is aside from whatever other security measures have been taken, of course. See More

Top Pro

Secure

Telegram uses an open source MTProto encryption protocol that provides complete end-to-end encryption for secret chats. To show off their confidence in the protocol the company behind Telegram has organized $200,000 and $300,000 challenges to break the encryption. So far there have been no winners. See More

Top Pro

Open source client apps

Client apps are open source, making whole service more trustworthy. See More

Top Pro

@mentions

You can ping people to get their attention by @mentioning them. See More

Top Pro

Voice and video messages

You can post voice and video messages if you are too lazy to write text messages. See More

Top Pro

Two-step verification

You can set up an additional password to your account, which can be reset by your email. You don't have to use an email if you do not want to. If you lose access to your email or forget your password, you will be able to reset it via text message if your account is over seven days old and will receive it within a week (in case you recover anything before then). See More

Top Pro

Games

Through bots like @gamebot or @gamee, you can play many games in Telegram, alone or with friends. See More

Top Pro

Banned in China

Servers used to be closed source, but this is no longer the case. Proof: https://github.com/wireapp/wire-server See More

Wire

Top Pro

Open sourced everything

cosmo's Experience

The interface is beautiful, and it's easy as hell to set up and get going. See More

Specs

Platforms:Web iOS Android OSX Windows Linux

Media:images / video / audio / GIFs

VoIP:Yes

Not subject to US government Gag Orders. See More

Top Pro

Based in Switzerland

Top Pro

End to End encrypted with fingerprint verification

Top Pro

Cross-platform desktop, mobile and web

Wire works on OS X, Windows, Linux, iOS, Android, and as a webapp. See More

Top Pro

Inline photos, music and videos

In addition to sharing images inline, Wire integrates with SoundCloud and YouTube to embed music and videos. See More

Top Pro

Clean, modern interface

Top Pro

Federated, decentralized server network

Wire's fully open-source architecture allows anyone to host a server and selectively federate with the rest of the network (including Wire's official servers). In turn, federation allows for decentralization, guaranteeing stable, robust, and uncompromised service beyond even the lifetime of the company. See More

Top Pro

Respects your privacy

Top Pro

Completely free for private use

Check out their pricing. It cannot be cheaper for secure private communication. See More

Top Pro

Intuitive user interface

Wire's user interface is quite intuitive to use, still it has everything required for a complete experience. Settings are very clean and allows you to turn on/off some features which might be disturbing for some, like link previews and emoji conversion. See More

Pidgin and its code is completely free and open source. Pidgin has no ads and no features behind a paywall. See More

Pidgin

Top Pro

Free and open source

Top Con

No native VoIP support

While there are plugins there is no built in support for VoIP in Pidgin which is time consuming to implement instead of being baked in from the jump. See More

Peter J. Mello's Experience

Pidgin isn't the most friendly piece of software to use, the very nature of being a multi-protocol messaging suite leads to some fragmented development issues, but it remains one of the only ways to maintain contact with a large contact list over the increasingly diverse instant messaging ecosystem. See More

Specs

Platforms:Windows, Linux, Android

Media:Video chat, Video, Image, Recording, Gif, Url links, Additional.

Message history:Optional, can

Messaging systems:Mulitple, see protocols and chat plugins

Pidgin not only supports IRC, it also supports plenty of other services such as AIM, Google Talk, MSN, ICQ and plenty of others. This way, you can have all of your conversations in the same app and won't have to deal with multiple chat windows being open. See More

Top Pro

Support for a wide range of additional chat services

Top Pro

Cross platform

The Pidgin instant messaging client is cross platform, working on Linux, Windows and OSX. See More

Top Pro

Highly customisable with plugins

Pidgin not only has a large plugin library built-in, but also an array of third party plugins for a variety of functions. See More

Top Pro

Convenient notification features

Like other quality IRC clients, Pidgin features notifications that the user can set in order to have a variety of things happen when the users is mentioned, such as an audio cue or changing the system tray icon. See More

Platforms:Windows, MAC, Linux

Ricochet

Top Con

Currently experimental

Specs

Message history:No

Messaging systems:Yes

surespot

Platforms:iOS, Android

Media:Yes

Platforms:Windows, Mac, Linux

Audio recording:Yes

Cryptocat

Media:Yes

Message history:Yes