Signal is a secure, free, and open source messaging application that uses end-to-end encryption to securely send and receive all kinds of communications with other Signal users. Using the Internet for all encrypted communication, Signal comes highly recommended by some of the top privacy and security advocates.
In this Signal review, we’ll look at the capabilities, usability, and security that Signal offers. We’ll also talk about how the design of the service provides extremely strong protection for your privacy. Signal is truly impressive, so let’s cut the chatter and dig in to the review.
Signal Pros and Cons
- End-to-end (E2E) encryption
- Encryption algorithms: Signal protocol, with Perfect Forward Secrecy (PFS) for text messages, voice messages, and video calls
- Open source software
- Disappearing messages (aka self-destructing messages)
- Published transparency reports
- Logs minimum amount of data
- Does not log IP Addresses
- Requires a telephone number to sign up
- Occasional problems with sending and receiving
Now we’ll briefly cover the main features of Signal encrypted messenger.
Here are some key features to consider when deciding whether the Signal app is right for you:
- Signal is generally considered the most secure messaging app in existence.
- 100% open source code. The code is available on GitHub.
- The Signal Messaging Protocol was independently audited in 2016.
- The service is fully GDPR compliant.
- Clients for Android, iOS, Mac OS, Windows, Linux.
In 2013, Moxie Marlinspike (real name Matthew Rosenfeld) founded Open Whisper Systems to develop the Signal app and protocol. In 2018, Marlinspike and Brian Acton founded Signal Messenger, LLC, to take over the development of both the Signal app and the Signal Protocol.
Signal Messenger, LLC is funded by the Signal Technology Foundation (aka Signal Foundation), a 501(c)(3) non-profit organization. All products of the Signal Foundation are published as free and open-source software.
Where is your Signal data stored?
When you use Signal, your data is stored in encrypted form on your devices. The only information that is stored on the Signal servers for each account is the phone number you registered with, the date and time you joined the service, and the date you last logged on. As Signal points out,
Notably, things we don’t have stored include anything about a user’s contacts (such as the contacts themselves, a hash of the contacts, any other derivative contact information), anything about a user’s groups (such as how many groups a user is in, which groups a user is in, the membership lists of a user’s groups), or any records of who a user has been communicating with.
All message contents are end-to-end encrypted, so we don’t have that information either.
This is great for your privacy, since no one can get any more information than that without physical access to your device or those of the people you communicate with.
This is different from apps like Wire messenger, which stores info about your contacts on central servers. However, it does mean that if you want to keep copies of your messages, you will need to configure Signal to back them up and restore them on your device.
Follow this link for instructions on using Signal backup and restore.
Third-party testing and audits of Signal
Even when a product is 100% open source like Signal, you don’t really know how good it is until someone checks it out. Here are some published findings by experts you can review to see how good Signal really is.
Signal security audits
A formal security analysis of the Signal protocol was conducted in 2016. According to that analysis, conducted by researchers from Germany, Switzerland, the United States, and Canada, there were no major flaws in the design. It showed that the protocol was cryptographically sound.
This analysis has been updated several times since, without changing the researcher’s conclusion that the protocol is sound. The last update was published in July, 2019.
Note: In September, 2019, a bug in the user interface of the Android version of the Signal app was discovered that could have allowed an attacker to eavesdrop on Signal users.
According to Vice.com, the bug was fixed the same day it was reported. This incident shows both the responsiveness of the Signal team, and the importance of keeping your copy of the Signal app and desktop updated.
Signal hands-on testing
For purposes of this Signal review, I tested out the mobile app for Android, along with the Linux desktop app.
Note: Signal is different than many other secure messaging apps in that you need to install and register it on a mobile phone before you can use it anywhere else. Therefore, I’ll address the mobile (Android) app first.
Installing Signal on an Android phone
Installing Signal on an Android phone involves downloading the app from Google Play and registering your phone using your telephone number. Some people object to registering using a phone number instead of an email address or anonymous username.
But registering with your phone number lets Signal connect easily to your phone’s contact list. Another benefit to this approach is that it lets Signal replace your phone’s built-in messaging app on Android devices.
Note: You can download an Android Signal APK here, and install the app that way, but Signal recommends against it unless you are an advanced user with special needs that would justify doing so.
Once you finish installing and registering your account, the Signal app will use your Internet connection to securely communicate with other Signal users by text, voice, video, group messaging, even file sharing, all using the secure Signal protocol.
Note: If you replace Android’s messaging app with Signal, you will need to distinguish between Signal users and non-users before sending messages. That’s because Signal cannot send encrypted SMS or MMS messages, meaning messages to non-Signal users will not be secure. Signal notifies you whenever you are messaging someone with a Signal account, and will offer you an easy way to invite non-users to join Signal when you connect to them.
Working with Signal
When you open Signal app you’ll see a list of your current phone contacts who are Signal users. The interface itself is clean and includes a wealth of information about the status of your contacts and your communications with them:
Tap the listing for a particular contact to open it. You’ll see the full thread of your conversation with that contact, the same as you would with any other messaging app.
But Signal has a number of features that can enhance your privacy, adjust the user interface, or just have fun adding things like animated stickers. Here are some of those features:
- Secure connection indicators – For iOS and Desktop Signal apps, all communications are always secure. For the Android app, the text input field for a conversation will show the words, “Signal message” and the Send icon will be blue and include an image of a closed lock when the connection is secure.
- Message reaction emojis – Quickly reply to messages with emoji reactions.
- View-once media – On mobile devices you can configure individual photos and videos to disappear after they have been viewed once.
- Group chats – Stay connected with your family and other groups of people.
- Insights – For Android users, a system that shows you what percentage of your Signal messages were sent encrypted.
- Disappearing messages – Set messages to disappear from both your and the recipient’s devices after a set amount of time has elapsed.
- Safety Numbers – Verify that you are communicating with the device you expect to be talking to by comparing safety numbers.
- Encrypted stickers – Add some fun without compromising your security.
Not only are the Signal mobile apps good looking and feature packed, they are also well made. Reviews are also good with Signal receiving ratings of 4.8 out of 5 stars at the Apple app store and 4.5 out of 5 stars at the Google Play store.
Signal Desktop clients
Signal officially supports the following desktop platforms:
- Mac OS
- Linux (64 bit and 32 bit)
Installing Signal Desktop for Windows or Signal Desktop for MacOS is just like installing any other app. It only takes a moment to download, and seconds to install.
Installing Signal Desktop for Linux isn’t a particularly user-friendly process. You need to be able to do a bit of work on the Linux command line, but after a couple of steps you’ll have Signal Desktop for Linux installed and ready to run.
Because your phone number is the only way Signal can identify you, you need to link your account to Signal Desktop. Launching Signal Desktop for the first time displays a QR code you can use to make the connection It will look something like this:
Follow the directions on the bottom of this window to connect Signal Desktop to your mobile device and sync your data between the two.
Once the desktop is synched to your mobile phone, you’ll see that clean Signal interface along with your contacts.
I’ll leave it up to you to explore what else the Signal Desktop can do besides displaying those fun stickers!
Signal Support is a searchable collection of around 70 articles addressing the most common questions and topics a Signal user might want information on.
For cases where this isn’t enough, you can hit the Contact Us link at the top of the page to submit a help ticket.
How secure and private is Signal
When it comes to security, the Signal messaging protocol is generally considered to be the most secure messaging protocol available. It is so good that many other messaging products, including Facebook Messenger, Skype, and WhatsApp, claim to have adopted the protocol for use in their own products.
When it comes to privacy, Signal is also a winner. As we discussed earlier, Signal only records three bits of information about their users. This is far less information than other services collect.
And you can take the privacy protections even one step further. This article has detailed instructions for registering a Signal account without disclosing your personal phone number.
Signal has published only one transparency report, which you can see here. The report, from October 2016, is incredibly detailed, even including transcripts of the subpoena used, and all the additional communication that passed back and forth.
It would be great to see more transparency reports, on a regular schedule, like we see with other services. For example, we noted regular transparency updates in our ProtonVPN review. As another example, Surfshark has a warrant canary that is updated daily.
Signal business features
Unlike other messaging services, such as Wire, Signal offers only a single, free version. There are no pricing tiers, no extra-cost features, and no business-specific features. This is consistent with the idea behind the product, which is to become the most secure messaging app available. Nothing more, nothing less.
The Signal pricing model is about as complicated as the list of Signal business features. The price for everything they publish is zero.
Everything is free and open source software.
While you can use everything from Signal free of charge, the Signal Technology Foundation is an independent 501c3 nonprofit. They are committed to developing open source privacy technology that is desperately needed in this world of endless surveillance. You can make a contribution to the organization by visiting this page, and following the directions you find there.
Conclusion: Consider using Signal today
Signal is clearly one of the leading secure messaging apps available today. While some people dislike the requirement to register with a phone number, the design of the whole system is such that it is hard to see this as a major problem. I have no qualms about recommending Signal to anyone investigating encrypted messaging services for personal use.
It is also a great alternative to WhatsApp that people are flocking to in 2021 as privacy concerns mount with WhatsApp and Facebook.
But you don’t need to take my advice on this. Users are flooding into the Signal camp from all directions. According to this February 2020 article at The Verge, The European Union has told its staff to switch to Signal for all its public instant messaging.
And let’s not forget these endorsements from big-name privacy and security advocates:
The most recent “big name” recommendation for Signal came from Elon Musk in response to the latest WhatsApp privacy issues.
What else is there to say?
Is Signal right for you?
It is hard for me to imagine someone reading this post for whom Signal would not be the right secure messaging app. And remember: If the need to register with a phone number really bothers you, read this article for alternatives to giving Signal your personal phone number.
One other reason not to try Signal: if most of the people you need secure messaging for are already using another secure messaging service like Wire or Telegram, it might make sense to join them there instead of trying to get them to all move to Signal.
Beyond those cases, I believe that anyone looking for a secure messaging service should try Signal now.
For alternatives, check out our roundup of the best encrypted messaging apps, or the other reviews below.
This Signal Messenger review was last updated January 2, 2023.
Signal, in a back door attack, had a few users hacked.
Disappearing messages can be seen as both an advantage and a disadvantage. Therefore, this function should be considered neutrally?
Here are more cons:
When looking at/evaluating a messenger, one should not only look at the issue of security as the sole criterion. There is also freedom, independence, data protection, privacy, sustainability, … Not everyone understands the same under “security” and there is also so-called pseudo-security:
Messenger quick overview (PDF downloadable in multiple languages):
Thoughts on “Alternatives to WhatsApp”:
And lastly, a unique overview of messenger comparisons:
Unfortunatley Back Restore doesnt work!!??!! Just lost over 2 gigs of backups when phone died and I had to use another.
Had backed up and created backup file. Had checked the 30-char code i had worked.
However, when you try to restore the data it just doesnt work. No error, no crash, it just doesnt work. Steer clear!!!
I learned that Elon Musk also recommends Signal.
Now, this makes me suspicious. I would say Snowden is trustworthy, but Musk is not.
This is classic ad hominem. Elon might be terrible, but he can still be right about something.
recent app download comments (1-22-22) for Signal app on GoOgle NotPlayNice Store states that Signal has been compromised, no longer e2e, no longer private, back door leak to Signal reps to allow government overreach and intrusion.
Signal CEO and founder Moxie Marlinspike announced today that he is stepping down and WhasApp Executive Chairman Brian Acton will take the helm until a replacement is found.
“Executive chairman and WhatsApp co-founder Brian Acton, who famously urged users to #DeleteFacebook in March 2018 and founded the Signal Foundation along with Marlinspike after he walked away from the social media giant in 2017 over a conflict with Facebook’s plans to monetize WhatsApp, will serve as the interim CEO while the search for a replacement is on.”
Brian Acton left Whatsapp and co-founded the Signal Foundation
Signal boasts high-grade encryption for data in transit,
but does not really protect the contents that have been exchanged.
Since early 2018 it refuses to provide sincere encryption of local storage with a user-supplied password.
See, e.g. https://github.com/signalapp/Signal-Desktop/issues/1850
Hello! Would you like to check on Olvid? Ditched Signal to Olvid, but it is still new and lack of peer review.
@magic8 their mobile clients were recently open sourced, which is good, but not their server. I suggest you consider going back to Signal.
What about Berty?
Nice write up. It seems people are missing the point.. or at least the point i use it for. Privacy not Security. If you are doing security you want to do other things along with end to end encryption or something totally different.
If you are doing something that is illegal enough for some one to get it and they got your or the recipients phone they can likely get it. My big deal is to keep my messages out of big tech’s hands. Since nothing is stored server side other than your Number, creation and login times.. problem solved. They know who i am when i am but not what it is…. unless the OS is yanking it out some how. Of course the other end needs signal as well.
If Govmnt does what the conspiracy theorists suggest and starts going into personal text messages to censor and such… signal and the like is where its at. Choose which ever you want, but choose one. I choose signal because it is Open Source.
i am strongly considering not using messaging with anyone who doesn’t use signal. Not because it is illegal but because big tech doesn’t need to know that I tell my family I’m going to be late for practice.
Also. take someones phone, point it at their face and when it unlocks text someone in their contacts something silly. Don’t use face/finger print
You can rapidly tap the lock/unlock button on an IPhone and disable the FaceId/TouchId, for situations where someone might force you to unlock your phone.
Posted same message on another thread before noticed that one.
It’s impossible to use Signal without exposing yourself to Google first. If you use client, 3rd party or from unofficial source, even Signal’s own website, you need to go throug Google’s recaptcha to acquire unique identify key, so the know which device is used and when. Google Play shop and AppStore does that same. BB always know, unless you have device which is not used anything else than Signal use!
I noticed in all of your reviews that we don’t address whether or not the messages can be retrieved off of your device if the device is unlocked (perhaps through the use of celebrite) and again, by using a tool like cellebrite, there is an attempted data extraction. There are dozens of articles online and none are clear and many are very conflicting. While I understand that if icloud back up is turned on if you’re using an iPhone that the data gets stored to your cloud, and possibly can be read, or on an android chat back up does the same. Assuming chat back ups and icloud are turned off, and the phone and the apps have passwords, and all the messages you have ever sent have been completely deleted (not through a wipe but just simply emptied the chat, could the entire history of the messages be retrieved although they were deleted? Specifically for threema and signal. Thanks
@Petro I am unsure about Threema, but the only way I can think of is that if someone using Signal has no security method in place (like a passcode or using a fingerprint scanner) to access their smartphone or tablet, then that is how a third party can view someone’s messages.
Signal also recommends user’s scan one another’s safety numbers to prevent potential middle man attacks. But if you cannot meet them in person, I think a call to your contacts through Signal can accomplish the same thing. Doing this will ensure any communications between you and them while using Signal will be secured.
If you delete your account, I believe all messages you sent are wiped and you can also delete certain messages that when deleted will no longer appear on the receiver’s end.
If you have any more questions, Signal’s support site is an excellent resource (link below). Have a good one!
I think I have found an app that is the basis of the idea behind the people at Signal’s wanting to try integrating cryptocurrency into their service. Status is an open source, peer-to-peer (P2P) encrypted messenger that comes with Ethereum wallet integration and is only available on iOS and Android, respectfully.
If I am right, I think Signal might have a hard time since the app relies on a centralized server network model. Unless their embracing cryptocurrency is a way to help lay the groundwork for Signal to somehow be converted to peer-to-peer? Status looks like a good service and may be growing in popularity, so it remains to be seen what happens.
Signal recommends users scan their contact’s safety numbers in order to prevent potential middle man attacks. This, however, is an interesting development.
Signal app is a free messaging and voice-talk platform similar to WhatsApp but with one most important difference “Privacy”. In fact, the tagline of the Signal messaging app is “Say hello to privacy”, a line that will resonate well with the users and make them want to trust the brand.
Dear Restore Privacy
I just watched this video [https://invidious.fdn.fr/watch?v=tJoO2uWrX1M] by ‘The Hated One’ where he says that Signal has betrayed us as it now will use Mobilecoin. Does this mean it is no longer private particularly at the server side? Should we ditch Signal in favor of Element or Session [I cannot make voice calls with Session]?
Every time we find a decent messenger something comes up. What say ye?
In my view, I think it best to wait since the effort is in Beta and it could end up going the way of Facebook’s proposed cryptocurrency. I think one huge disincentive is the recent clampdowns on cryptocurrencies by the U.S. and other governments as of late that has resulted in large drops in their value.
The kind of scrutiny on the part of government regulators a Signal-MobileCoin venture would invite also makes it unjustifiable both of which are huge drawbacks. These reasons alone might be enough reason for Signal to dump this effort.
Before Christmas of last year, a story ran on BBC and other news outlets that stated an Israeli Digital Intelligence Company named Cellebrite was able to hack into Signal by breaking it’s encryption. This is false and Signal Foundation was not contacted for comment or given the ability to respond. Here is a link to their response about Cellebrite’s claim.
I think they have their foundation to say Signal was interupted, we don’t see why not. And Signal is jurisdiction of America. Nothing impossible until it happens. So nothing wrong if we are aware of this noteworthy exception.
This should prove interesting
Internet Privacy [Signal, Tor, etc], Funded By Govt
We need to talk about mathematical backdoors in encryption algorithms
Signal Points of interest are as follows:
Signal has been verified to be funded by the U.S. Govt.
The U.S. is part of Five Eyes.
Signal Servers are centralized in the U.S.
Signal runs on Amazon AWS cloud service — and Amazon is itself a CIA contractor
So more than likely the Signal encryption protocol can be accessed by the U.S. Govt; They fund it, they own it, they control it.
Signal is not on F-Droid
More investigation maybe warranted.
I just looked and Signal is on F-Droid. There isn’t anything I can see in either of those two articles you link to that points to Signal being funded by the U.S. government. The feds may have funded the research for the encryption and servers Signal uses but that’s not the same thing. Also, I do not think a message or any cloud or server-based service being located in the U.S. is necessarily a bad thing.
Consider that there are no laws in the U.S. requiring VPN’s, message services, or any server-based company (like those who provide clouds) to keep records of their user’s activities. This being the case, that enhances, and does not detract, user privacy. European countries with strong national privacy laws, Switzerland and Germany, may have laws on their books requiring said services keep records or the E.U. might.
I realize the concerns with intelligence agencies, but if they really want to spy on you they will find ways to do so. Suspicion is certainly warranted, but I think as long as you are a law-abiding citizen and don’t do anything illegal, I don’t think you will have a problem.
Amazon is a well known CIA contractor.
Signal servers are stored in the US.
CIA founded Signal research.
Signal Creator Moxie Marlinspike is a well know hacker in the scene circa 2000-2010 well known for building tools to hack and break encrypted data transmission in the SSL protocol way before SIgnal was invented.
A Hacker create tools 20 years ago to break SSL encryption used in millions of websites.
–> Then creates a protocol for “secure comunications” founded by NSA and CIA.
–> Then release Signal, an app the claims have unbreakeable encryption.
–> Then most industries messaging apps include this code to secure the communication.
–> Now step down as a CEO and the newest CEO sold an app (Whatsapp) to the biggest
data miner in history also founded by 3 letter agencies in the US, META (Facebook).
Would ANYONE trust Signal knowing who invented it and founded it????
What Facebook is to social media data/intel mining, Signal is the same but for “Encrypted” communications.
Let’s have this conversation 10 years from now.
Well, watching a video from an interview of a gentleman charged in the 6th of the year fiasco in which he reported that B B somehow breached sgnl? if so, it would not surprise me. Just amazing our own tnemnrevog is eavs drpg on its own….. No account a b i l i t y. I thought the ctzens were in charge and B B works for us. LOL
Here’s my issue. iPhone user. If Face ID does not work, signal prompts you to enter your iPhone code. Well if your kid or someone knows your phone code, they also know your signal code. Not private in “real world.”
Sorry for the late response. My understanding is that Signal is going to try to make a feature where people who sign up for it won’t have to use a phone number. I think a better way would be to issue an account number, like the VPNs Mullvad and IVPN do, instead. Otherwise, Signal has a PIN or biometric screen lock feature that can prevent a third party from accessing or using it.
There is an issue regarding contact research with Signal.
This will be shown around the 18:25-27 minute mark.
Signal’s response to a grand jury’s subpoena for user data.
I use ShazzleChat. Safe and completely private.
Is it open source? I don’t see any webpages indicating it has made it’s source code public. If not, you may want to look elsewhere since if ShazzleChat is proprietary the makers can change the terms and conditions and then use it to mine your data.