how url shortener works

how url shortener works


I wonder how a URL Shortener works, like how they extract the text from address bar and map it to correct URL, later redirect it. What programming language do they use? How do they maintain the his..

I am trying to create an app that will be able to take a picture of a QR code and then open up a webpage on my server. The problem is that when I try to run this in Android Studio, it says "Unfortunately, MyApp has stopped". Here's what I have so far:

Short URL The URL shortener on Meta-Wiki URL shortening is a technique on the World Wide Web in which a Uniform Resource Locator (URL) may be made substantially shorter and still direct to the required page. This is achieved by using a redirect which links to the web page that has a long URL. For example, the URL  can be shortened to "  and the URL " URL_shortening" can be shortened to  Often the redirect domain name is shorter than the original one. A friendly URL may be desired for messaging technologies that limit the number of characters in a message (for example SMS), for reducing the amount of typing required if the reader is copying a URL from a print source, for making it easier for a person to remember, or for the intention of a permalink . In November 2009, the shortened links of the URL shortening service Bitly were accessed 2.1 billion times.

Other uses of URL shortening are to "beautify" a link, track clicks, or disguise the underlying address. Although disguising of the underlying address may be desired for legitimate business or personal reasons, it is open to abuse.

Some URL shortening service providers have found themselves on spam blocklists , because of the use of their redirect services by sites trying to bypass those very same blocklists. Some websites prevent short, redirected URLs from being posted. Other websites allow them but only if the user provides additional information such as the full URL, the date and time of posting, etc.

URL shorteners are also used for malicious purposes. They are often used by spammers to shorten the length of email addresses. Spam bots use these shortened URLs to send out millions of emails at once. Many people who receive spam messages with shortened URLs assume that they are infected with malware.

In February 2011, Google announced that it would no longer support the use of its own URL shortener,, due to security concerns.

In March 2012, Facebook began testing a new feature called Instant Articles, which allows publishers to post articles directly to Facebook without having to first publish them on their website. Unlike traditional RSS feeds, Instant Articles require users to click through to the publisher’s site before reading the article. As part of the process, Facebook generates a unique URL for each article that includes a shortened version of

Some websites create short links to make sharing links via instant messaging easier, and to make it cheaper to send them via SMS . This can be done online, at the web pages of a URL shortening service; to do it in batch or on demand may require the use of an API. 

A few well-known websites have set up their own URL shortening services for their own use – for example, Twitter with, Google with, and GoDaddy with

Shortened URLs are sometimes used by search engine optimization (SEO) experts to improve the ranking of a webpage. For example, when a company wants to promote a product, it will create a landing page with a link to the product's website. However, this link could be too long for some people to type into a search box. Instead, SEO experts might suggest creating a shortened link instead. When someone searches for keywords related to the product, the shortened link will appear higher in the results.

In URL shortening, every long URL is associated with a unique key , which is the part after its top-level domain name . For example, . Not all redirection is treated equally; the redirection instruction sent to a browser can contain in its header the HTTP status 301 (Moved Permanently), 302 (Found), 307 (Temporary Redirect) or 308 (Permanent Redirect

There are several techniques to implement a URL shortening. Keys can be generated in base 36 , assuming 26 letters and 10 numbers. In this case, each character in the sequence will be 0, 1, 2, ..., 9, a, b, c, ..., y, z. Alternatively, if uppercase and lowercase letters are differentiated, then each character can represent a single digit within a number of base 62 (26 + 26 + 10). In order to form the key, a hash function can be made, or a random number generated so that key sequence is not predictable. Or users may propose their own custom keys. For examplerefshirt can be shortened to :

and javascript: URLs are not supported for security reasons (to combat attacks like cross-site scripting session hijacking ). Some URL shortening services support the forwarding of mailto URLs, as an alternative to address munging , to avoid unwanted harvest by web crawlers bots . This may sometimes be done using short, CAPTCHA -protected URLs, but this is not common.