When comparing Signal vs Flowdock, the Slant community recommends Signal for most people. In the question“What is the best team chat software?” Signal is ranked 2nd while Flowdock is ranked 4th. The most important reason people chose Signal is:
Signal uses an advanced end to end encryption protocol that provides privacy for every message every time.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Provides security and privacy
Signal uses an advanced end to end encryption protocol that provides privacy for every message every time.
Pro Free and open source
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.
Pro SMS/MMS support
Signal can be your default SMS/MMS text messenger. Encryption is not possible when sending SMS to your contacts, however.
Pro Supports encrypted group chats
Pro Supports sharing of various different media types
Signal supports: emoji, pictures, videos, audio, contacts, any location and GIF.
Pro Recommended by Edward Snowden
Edward Snowden uses this messenger and recommends it to everyone who is concerned about his privacy.
Pro Message mirroring on Signal Desktop
Signal Desktop is a Chrome extension that allows you to mirror messages from your phone, including replying.
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.
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
Pro Works everywhere in every country
Unlike most messenger apps, Signal works reliably in all countries by securely circumventing internet censorship.
Pro Annonymous Sender (Encrypted)
The sender credentials can be encrypted with the rest of the message, leaving only the recipient address readable by the Signal server. Even if Signal wanted they couldn't see who is talking with who by this mean.

Pro Threaded discussions
An easy & simple interface to filter chat discussion into separate threads.
Pro Drag and drop file sharing
Files can be dragged and dropped in to the flow dock screen for upload.
Pro Multi-platform
Browser Based, as well as:
- iPhone and iPad App
- Android App
- Mac OS X App
Pro Stored chat history
Content and discussions are stored forever.
Pro Smart pastes & code syntax highlighting
Pro Private chat option
Able to speak privately/talk head-to-head.
Pro Notification system
A specific user or everyone in the channel can be notified via @user or @everyone respectively.
Pro A full developer API
Flowdock API allows developers the freedom to create custom integrations.
Pro Create and assign PRs from Flowdock
You can interact with Github directly from Flowdock to create PRs.
Pro Free for teams of five, non-profits and students
Pro Data exports
Back up conversations and files fully at any time.
Pro Add Tools
On top of our 50+ custom integrations, easily integrate any tool that sends emails or generates RSS feeds, as well as having the option to build a custom integration with Flowdock's API
Pro Status updating
Allows co-workers to know what you’re up to "/status I'm busy today!"
Pro Google Apps Integration
Google Apps get a Flowdock link to the Apps tool-bar and won't have to separately manage users
Pro Typo Fix-ups
Pro Able to host users external to your team
When working with stakeholders (clients or partners) you can add organizations to manage internal privacy
Cons
Con Needs access to your phone number and contacts to work
Con Single device
Signal can only be registered to one mobile device at a time. But you can link Signal to Signal Desktop.
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.
Con Servers hosted in the US
A security risk due to National Security letters, which require giving up data to the US state, and making it illegal to disclose that.
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.
Con Cannot work w\o Google services
Signal relies on Google services for push notifications so although it is encrypted and open source it needs proprietary component to work. That means you can't use Signal on some custom Android ROM (preferably rooted for full control) without Google apps installed.
Con Uses message mirroring
Con Proprietary (non-free/libre)
Con No self-hosting available
If you are worried about third-parties getting access to your data you should consider self-hosting. With self-hosting you are in control over where your data is stored, who has access to it. You will also not be vulnerable to exploits of a third-party provider.
Con Buggy android app
Google sign up didn't work, then after going to the website to do the sign up, the invite team members screen was broken.
Con Free only for small teams, non-profits or students
Unless it's used by a team of less than five people, a non-profit or students, Flowdock will cost $3/mo per person.
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