1. PHP (use with preg_match)

%^(?:(?:https?|ftp)://)(?:\S+(?::\S*)?@|\d{1,3}(?:\.\d{1,3}){3}|(?:(?:[a-z\d\x{00a1}-\x{ffff}]+-?)*[a-z\d\x{00a1}-\x{ffff}]+)(?:\.(?:[a-z\d\x{00a1}-\x{ffff}]+-?)*[a-z\d\x{00a1}-\x{ffff}]+)*(?:\.[a-z\x{00a1}-\x{ffff}]{2,6}))(?::\d+)?(?:[^\s]*)?$%iu

2. PHP (with validate filter)

if (filter_var($url, FILTER_VALIDATE_URL) !== false)...

3. Python

http[s]?://(?:[a-zA-Z]|[0-9]|[$-_@.&+]|[!*\(\),]|(?:%[0-9a-fA-F][0-9a-fA-F]))+

4. Javascript

/((([A-Za-z]{3,9}:(?:\/\/)?)(?:[\-;:&=\+\$,\w]+@)?[A-Za-z0-9\.\-]+|(?:www\.|[\-;:&=\+\$,\w]+@)[A-Za-z0-9\.\-]+)((?:\/[\+~%\/\.\w\-_]*)?\??(?:[\-\+=&;%@\.\w_]*)#?(?:[\.\!\/\\\w]*))?)/

5. HTML5

<‍input type="url" /‍>

5.1 Perl

^(((ht|f)tp(s?))\://)?(www.|[a-zA-Z].)[a-zA-Z0-9\-\.]+\.(com|edu|gov|mil|net|org|biz|info|name|museum|us|ca|uk)(\:[0-9]+)*(/($|[a-zA-Z0-9\.\,\;\?\'\\\+&%\$#\=~_\-]+))*$

5.2 Ruby

/\A(?:(?:https?|ftp):\/\/)(?:\S+(?::\S*)?@)?(?:(?!10(?:\.\d{1,3}){3})(?!127(?:\.\d{1,3}){3})(?!169\.254(?:\.\d{1,3}){2})(?!192\.168(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[a-z\u00a1-\uffff0-9]+-?)*[a-z\u00a1-\uffff0-9]+)(?:\.(?:[a-z\u00a1-\uffff0-9]+-?)*[a-z\u00a1-\uffff0-9]+)*(?:\.(?:[a-z\u00a1-\uffff]{2,})))(?::\d{2,5})?(?:\/[^\s]*)?\z/i

6. Go (use the govalidator IsURL())

package main
 import (
         "fmt"
         "github.com/asaskevich/govalidator"
 )
 func main() {
         str := "http://www.urlregex.com"
         validURL := govalidator.IsURL(str)
         fmt.Printf("%s is a valid URL : %v \n", str, validURL)
 }

7. Objective-C

(http|https)://((\\w)*|([0-9]*)|([-|_])*)+([\\.|/]((\\w)*|([0-9]*)|([-|_])*))+

8. Swift

((?:http|https)://)?(?:www\\.)?[\\w\\d\\-_]+\\.\\w{2,3}(\\.\\w{2})?(/(?<=/)(?:[\\w\\d\\-./_]+)?)?

8.1 Use it in a function:

func canOpenURL(string: String?) -> Bool {
    let regEx = "((https|http)://)((\\w|-)+)(([.]|[/])((\\w|-)+))+"
    let predicate = NSPredicate(format:"SELF MATCHES %@", argumentArray:[regEx])
    return predicate.evaluateWithObject(string)
}

8.2 Usage:

if canOpenURL("http://www.urlregex.com") {
    print("valid url.")
} else {
    print("invalid url.")
}

9. Swift (use canOpenURL)

UIApplication.sharedApplication().canOpenURL(urlString)

10. Java

^(https?|ftp|file)://[-a-zA-Z0-9+&@#/%?=~_|!:,.;]*[-a-zA-Z0-9+&@#/%=~_|]

11. VB.NET

(http(s)?://)?([\w-]+\.)+[\w-]+[.com]+(/[/?%&=]*)?

12. C#

^(ht|f)tp(s?)\:\/\/[0-9a-zA-Z]([-.\w]*[0-9a-zA-Z])*(:(0-9)*)*(\/?)([a-zA-Z0-9\-\.\?\,\'\/\\\+&%\$#_]*)?$

13. MySQL

SELECT field FROM table 
WHERE field 
REGEXP "^(https?://|www\\.)[\.A-Za-z0-9\-]+\\.[a-zA-Z]{2,4}

14. Bonus: What does the following regex do?

/^1?$|^(11+?)\1+$/