What is a “query string”?
A “query string” is one of several methods of passing data from one web page to another. You’ve probably seen URLs that look like this:
`http://www.calendar.com?day=25&month=1&year=2018`
That URL contains two parts, separated by the “`?`” character. The part before the “`?`” mark is the link and the part after the “`?`” mark is data being passed to the link.
In effect, the URL above says to go to the website `www.calendar.com` and pass the data

|  | day = 25 month = 1 year = 2018

Who knows what `calendar.com` is going to do with that data, but it’s reasonable to assume that it has something to do with the date “January 25, 2018.”
When you look at the URL in this example, the query string is introduced by the “`?`” mark, followed by the actual query string which is made up of `name=value` data pairs, each separated by the “`&`” character:
`http://www.calendar.com?day=25&month=1&year=2018`
The “`&`” character is commonly pronounced “and” in computer programming languages, so you can loosely think of that query string like this:

|  | ? (pass the following data:) day = 25, and month = 1, and year = 2018

In this example, each of these `name=value` pairs shows numerical values, but values can contain numbers, characters, and symbols as well. The month value could just as easily have been either of these:
`month=jan
month=[January]`
It’s really up to the target website to determine what the data means and how you need to pass it in.
Query strings are used in several places in ClickMagick. You’ll find them in tracking pixels, Postback URLs, affiliate network integration, and the Funnel Builder.
You may need to edit query strings at times, or add a new `name=value` parameter. For example, let’s assume you have a URL and you need to add this ClickMagick integration parameter:
`s1=[clickid]`
If the URL doesn’t have a query string yet (meaning there’s no “`?`” mark yet), you’ll need to create the query string by adding a “`?`” mark followed by the new parameter:
`http://www.website.com?s1=[clickid]`
On the other hand, if the URL already has a query string (meaning there’s already a “`?`” mark), you would simply add the new parameter to the end using the “`&`” character:
`http://www.website.com?id=475&s1=[clickid]`
You can search the web for a much more thorough discussion of query strings, but this should get you through 97% of the situations you’ll ever run across.
Encoded Query Strings
One thing you’re sure to run into is “encoded” query strings. These are query strings where some characters are replaced with a more “machine friendly” form. For example, the space character will typically be replaced with `%20`, colons with `%3A`, and slashes with `%2F`. Don’t be surprised if you see `http://` encoded as`http%3A%2F%2F`. Check out W3Schools.com’s complete list of URL encodings.
HTML has a different way of encoding characters using named “entities.” For example, the “`&`” character itself will often be replaced with `& amp;`. This creates some unusual looking query strings, especially when you paste an otherwise normal looking link into a Page Builder and you see your `name=value` pairs separated by `& amp;` entities when you view your page source. You can find an extensive list of these HTML entities at W3Schools.com.
You won’t need to worry about encoded query strings in ClickMagick, but at least you’ll know what those `%##` and `&entity;` encodings are when you do see them.
Value-less Parameters
Another thing you’ll see are query strings where the parameters don’t have any values, such as:
`http://www.calendar.com?day=&month=&year=`
Parameters without values are perfectly fine. It just means they aren’t specified. For this `www.calendar.com` example, this might simply mean “display today” since an actual date is not specified. Using value-less parameters is quite common, so don’t let it confuse you if you see them.
Tip: If you want to pass a query string from a tracking link to its Primary URL, you can use the `[query_string]` token. See the section on Passthrough Tokens in this FAQ:

|  | What data can I pass to the URLs I promote?

Note: For a more complete description of query strings, take a look at this Wikepedia entry:

|  | History and Use of Query Strings