How do I see which version of Swift I'm using?

I just created a new Swift project within Xcode. I am wondering which version of Swift it's using.

How can I see, in Xcode or the terminal, what version of Swift I am using inside my project?

What I do is say in the Terminal:

$ xcrun swift -version

Output for Xcode 6.3.2 is:

Apple Swift version 1.2 (swiftlang-602.0.53.1 clang-602.0.53)

Of course that assumes that your xcrun is pointing at your copy of Xcode correctly. If, like me, you're juggling several versions of Xcode, that can be a worry! To make sure that it is, say

$ xcrun --find swift

and look at the path to Xcode that it shows you. For example:

/Applications/Xcode.app/...

If that's your Xcode, then the output from -version is accurate. If you need to repoint xcrun, use the Command Line Tools pop-up menu in Xcode's Locations preference pane.

Project build settings have a block 'Swift Compiler - Languages', which stores information about Swift Language Version in key-value format. It will show you all available (supported) Swift Language Version for your Xcode and active version also by a tick mark.

Project ► (Select Your Project Target) ► Build Settings ► (Type 'swift_version' in the Search bar) Swift Compiler Language ► Swift Language Version ► Click on Language list to open it (and there will be a tick mark on any one of list-item, that will be current swift version).

Look at this snapshot, for easy understanding:

With help of following code, programmatically you can find Swift version supported by your project.

#if swift(>=5.3)
print("Hello, Swift 5.3")

#elseif swift(>=5.2)
print("Hello, Swift 5.2")

#elseif swift(>=5.1)
print("Hello, Swift 5.1")

#elseif swift(>=5.0)
print("Hello, Swift 5.0")

#elseif swift(>=4.2)
print("Hello, Swift 4.2")

#elseif swift(>=4.1)
print("Hello, Swift 4.1")

#elseif swift(>=4.0)
print("Hello, Swift 4.0")

#elseif swift(>=3.2)
print("Hello, Swift 3.2")

#elseif swift(>=3.0)
print("Hello, Swift 3.0")

#elseif swift(>=2.2)
print("Hello, Swift 2.2")

#elseif swift(>=2.1)
print("Hello, Swift 2.1")

#elseif swift(>=2.0)
print("Hello, Swift 2.0")

#elseif swift(>=1.2)
print("Hello, Swift 1.2")

#elseif swift(>=1.1)
print("Hello, Swift 1.1")

#elseif swift(>=1.0)
print("Hello, Swift 1.0")

#endif

Here is result using Playground (with Xcode 11.x)

Open the Terminal and write:

swift -version

From Xcode 8.3 onward Build Settings has key Swift Language Version with a value of swift version your target is using.

For older Xcodes use this solution, open terminal and type following command(s)

Case 1: You have installed only one Xcode App

swift -version

Case 2: You have installed multiple Xcode Apps

• Switch active developer directory (Replace Xcode_7.3.app from following command with your Xcode app file name from Application directory for which you want to check swift version)

   sudo xcode-select --switch /Applications/Xcode_7.3.app/Contents/Developer
  

• Then

   swift -version
  

NOTE: From Xcode 8 to Xcode 8.2.x you can use swift 2.3 even though Xcode 8 uses swift 3.x as default swift version. To use swift 2.3, just turn on flag Use Legacy Swift Language Version to YES from Build Setting and XCode will use Swift 2.3 for that project target.

You can see and select which Swift version Xcode is using in:

Target -> Build Settings -> Swift Language Version:

This is available in Xcode 8.3 and Xcode 9 (haven't checked older versions)