When comparing Hangouts vs SwiftKey, the Slant community recommends SwiftKey for most people. In the question“What are the best Android apps?” SwiftKey is ranked 21st while Hangouts is ranked 42nd. The most important reason people chose SwiftKey is:
The prediction engine of SwiftKey is continuously being improved by using data from social networks, text messages or even emails from the user's device. Predictions appear above the keyboard as soon as a letter is typed. By adjusting to the user's writing habits and style, it really helps to save time when writing.
Specs
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Pros
Pro Save and sync your chats across multiple devices
Start chatting on your phone, then on your computer, then on your tablet seamlessly!
Pro No need to create a separate account if you use any other Google service
Hangouts uses Google account credentials. If you use any other Google service, then you already have an account set up.

Pro Group video support
If you have signed in your Google account, Hangouts allows making video calls with up to 10 people or one-on-one. There are business, education and government solutions that increase the participant count to for video calls to 15 as well as offers support for those accounts.
Additionally, you can switch between using either the front-facing or rear-facing camera on your phone or tablet.

Pro Free and cross-platform
Google offers all features of Hangouts completely free on iOS, Android and web with quick and reliable sync across all platforms. It's also tightly integrated in other Google services - it can be accessed from services such as Gmail, Google+, Chrome.
While the standard Hangouts offering is completely free, there are business, education and government solutions that increase the participant count to for video calls to 15 and offers support that may cost money.
Pro Chrome browser extension
Use the extension on any computer you can run Chrome browser to text from your computer or tablet!

Pro Excellent read receipts in group chat
It's possible to know what each and every participant of the group has read. Their icons are displayed below the last message.

Pro Can share animated GIFs
If you have gifs in your mobile phone, you can share them in the conversation and your partner will be able to see it animated in the chat.
Pro Google Voice integration
Google Voice is a service that enables making and receiving free phone calls within US. Google Voice forwards incoming calls to all connected devices and allows placing calls from any of the connected devices, but they will show as coming from the Google Voice number.
Hangouts completely integrates Google Voice, allowing you to place calls and receive texts and voicemail from all of your devices. The Hangouts app for Android also includes a needed dialer for making calls with the users Google Voice number.
Pro Free calls to US and Canada from anywhere in the world
Hangouts app for Android can be extended with an optional dialer for making calls. Most calls to US and Canada are free and international calls have cheap rates.
A Google Voice account will be needed in order have a number that allows these calls to be made.
Pro Advanced status sharing
Hangouts can inform about the status of other users including what device they are currently using, whether they are in the middle of a call and when were they last seen. This allows making sure that you're not disturbing someone when initiating a conversation. It's possible to granularly turn off status sharing.
Pro Video tools
Hangouts can add different effects and overlays to video calls that can be viewed on your device. Unfortunately, they can't be set from your phone.
Pro Seamless integration with OK Google for voice control and typing
Hangouts can be used completely hands free, even if the app is not open and the phone is locked: "OK Google, send a Hangouts message to Mary".
Pro Highly acclaimed for its constantly improving prediction engine
The prediction engine of SwiftKey is continuously being improved by using data from social networks, text messages or even emails from the user's device. Predictions appear above the keyboard as soon as a letter is typed. By adjusting to the user's writing habits and style, it really helps to save time when writing.
Pro Can be customized with plenty of themes available
Swiftkey offers a wide range of different themes to add personality to your keyboard (some are free.. others paid for via in app purchases).
Pro Has a large number of languages available
Has 61+ languages available that can be downloaded. So chances are the languages you need will be available.

Pro Multiple simultaneous languages
Keyboard can integrate multiple languages into one seamless autocorrect engine.
Pro Can be resized to as large or as small as you want
You can choose between five different sizes to resize the keyboard.
Pro Can be undocked
The feature may seem odd but the ability to undock the keyboard is extremely useful in certain situations. For example when creating content or using difficult websites.
Pro Ad-free
SwiftKey is competely ad-free.

Pro Can be customized to have a numbers row in easy reach
Users can optionally display a number pad above the keyboard.

Pro Gestures typing or tap typing
Swiftkey supports both popular methods of typing. Either way the methods integrate perfectly with the predictions featured above the keyboard.
Pro Fast access to Emojis
When users type the name of the desired Emoji, a small list will come up where the right one can be selected.
Pro Free
Swiftkey is free to download and use, though there are in app purchases to unlock more features.
Pro Users can view in-depth usage statistics
SwiftKey will even provide you exciting data about how you type such as a heatmap.
The more you use SwiftKey, the more your heat map will transform from perfect circles into blobs where you tend to press. From the Heatmap you'll know where you tend to make mistakes and how SwiftKey is improved. Other stats provided include:
- Distance flowed in meters
- Keystrokes saved
- Typos corrected
- Words completed
Pro Supports Google voice dictation
Even though SwiftKey is a third party keyboard, Swiftkey still uses the preferred Google voice dictation.
Pro All the typing information saved from SwiftKey is synced across devices
Any learned words, phrases (inc. email addresses) will be backed up to the cloud and available across multiple devices.
Pro Various convenient layouts available, also for tablets
Among the layout choices is a split keyboard which anchors each half to the lower corners of the screen, where one would naturally hold a tablet device while typing, with the option to place a dedicated 10-key number pad in the unused space between them.
Pro Cloud backup
Pro Social Account Integration for learning new languages
Cons
Con Transitioning to corporate orientation
Google is turning Hangouts in to a Slack competitor. It's unclear what the future of Hangouts is, but Google has said the consumer Hangouts we now have 'isn't going anywhere.'
Con Lack of end to end encryption
Communications are encrypted between client and Google servers but not from sending client to receiving client. This means that there is still a possibility for someone other than the receiver to read your message if they have access to internal Google servers. But it allows also lightweight chat history search, spam protection and other features.
Con Is owned by Google
Google is a cooperation that earns money from collecting data and breaching privacy.
Con Poor interface
The app tends to lag, the design can be confusing and considering that another app has to be installed that supplies another icon in the home screen in order to get a dialer for calls in Hangouts, overall it is very confusing and cluttered.
Con No rich text editing
On Android you can receive messages with bold or italic text. However, you cannot bold or italicize text on Android, only on iOS devices or via the web interface.
Con No way to moderate groups
If a member of a group chat room becomes disruptive, or there's some other need, there's no way in Hangouts to remove somebody from an existing chatroom. Similarly, if somebody is no longer active, there's no way to remove that user from the chat room to make slot for new active members.
Con Buggy video calls
Whether video calls work on your device is pure lottery, and there's nothing you can do to fix it.
Con Poor indication of who's online
There is no way to find out if a person in your contact's list is online or not in the Android app.

Con Poorly manages data
Doesn't cache images well either received or sent. Often users will see the sent images re-downloading, same for conversations.
Con API support was removed
This change closed options for integrations and connections between similar apps.

Con Not available on Windows Phones
There is no Hangouts app for the Windows Phone.
Con Doesn't support sending voice notes or video recordings
Currently there is no built in function that supports creating and sending voice notes or video recordings.
Con No customer support
Free product, you're on your own.
Con Won't send SMS/MMS anymore
They removed support for sms/mms. The same goes with integration to hangouts.
Con No SMS/MMS backup
They don't have options to backup sms to cloud.
Con SMS messages sent from the web app can't be sent outside North America
SMS messages sent from the web app can only be sent to number in America and Canada - sending to foreign numbers won't work, although you can still receive texts from anywhere.
Con Swipe recognition not as smart as Swype
It requires much more precision, if you miss one letter you have little chance of having the desired word, which makes it difficult to use in some situations.
Con Privacy, automatically saves unknown words
E.g. passwords entered in plain text fields, place names, people names etc.
Con High data bandwidth usage
This product consumes several MB per week, sometimes per day. The fact that SwiftKey doesn't fix the bug despite many similar reports is not really reassuring.
Con No language separation or weighing
If you load several languages, you can choose any keyboard for any of them, but it won't help the recognition algorithm, which insists on giving other language words in the most absurd situations.
Again, no help from their support to arrange the situation.
Con Cannot remove some options
You cannot remove the emojis or Info button from the keyboard.
Con Themes are in app purchases
Like most third party keyboards, Swiftkey offers tons of themes but of course they cost money and have to be purchased through the app.
Con The smallest layout is too big
Con High processor/memory usage makes it unusable on older devices
SwiftKey is extremely resource-intensive compared to many of its competitors, and will often lag even on high-end smartphones.
Con Predicting and inserting word combinations faulty
Recent update enabled Swiftkey to predict short word combinations. In principle this should be quite convenient, but so far it turns out this new algorithm is defective and way too aggressive. Too often it inserts combinations that are completely meaningless, or inserts English combinations in Dutch sentences or the other way around. Has almost doubled the amount of corrections needed.
Con Bought by Microsoft
Will undoubtedly lead to less innovation.
