I recently came across an article on Mobile Orchard about connecting click-throughs to app sales, which is a rather ingenious idea using the affiliate program LinkShare to create trackable links. As Apple record and report orders that come via these referral links, you can actually see the number of sales (not just views of the App Store page) that resulted from follows of the link. Plus you get a 5% cut of the sale!

I’m doing some experiments with advertising my live looper app Loopy lately, and want a way to track the success of various approaches. It occurred to me that the totally freeform nature of the LinkShare “signature” field (which you can use to track traffic sources) lends itself to an even more flexible approach than that presented in the Mobile Orchard article.

Here’s a way to use that signature field to report the domain name of any referrer who links either to the app page, or to a download link (like, say, http://loopyapp.com/download).

This way, if, say, TUAW link to your app site, if someone clicks through then clicks the download link on your app site and buys, the resulting order will be reported as coming from TUAW. If someone clicks through from your Facebook page, it’ll come up as coming from Facebook. You can even modify the script further to report more precise details (like the path), if you like.

It assumes you’re using PHP, but the principle’s the same for any other language (BYO code, though ;-)).

Step 1: Sign up to LinkShare

First, if you haven’t already, Sign up to the LinkShare program — Once you’ve created a LinkShare account, join the Apple affiliate program via the “Programs” tab. After 3 days, you’ll get an email welcoming you to the program, and you’ll be good to go.

Step 2: Create a product link

Once you’re admitted to the program, open up the “My Advertisers” sub-tab from the LinkShare Programs tab, and open the “Link Maker Tool”. This lets you search for products, and create a link that will open up your app’s App Store page, and will be associated with your LinkShare account.

Step 3: Create a download redirection script

Now we’re going to set up a script on your app site which will redirect the visitor to the URL you just created (which in turn, redirects straight to the App Store page). It’ll add a “signature” parameter to the URL, which corresponds to the original referrer, so you can track where orders came from.

Create a file called ‘download.php’ in the root of your app site, with the following content, with your LinkShare URL inserted where indicated:

<?php
// Replace the following URL with the LinkShare URL you created
$linkshare_url = "http://click.linksynergy.com/fs-bin/stat?id=/yGrgMJzFG0&offerid=146261&type=3&subid=0&tmpid=1826&RD_PARM1=http%253A%252F%252Fitunes.apple.com%252Fapp%252Floopy%252Fid300257824%253Fmt%253D8%2526uo%253D4%2526partnerId%253D30";
 
session_start();
$referer = $_SESSION['original_referer'];
if ( !$referer ) $referer = $_SERVER["HTTP_REFERER"];
 
if ( $referer ) {
    $signature = preg_replace("@https?://(?:www\.)?([^/]+?)(?:\.com)?/.*@", "$1", $referer);
} else {
    $signature = preg_replace("@^(?:www\.)?(.+?)(?:\.com)?$@", "$1", $_SERVER["HTTP_HOST"]);
}
 
$signature = preg_replace("@[^a-zA-Z0-9]@", "", $signature);
 
header("Location: ".$linkshare_url."&u1=".$signature);
?>

This script looks for the original referrer in a session variable (which we’ll set up in the next step), so that the domain of the site that links to your app site is used, not just your app site’s domain. Then it creates a properly-formatted signature parameter (just alphanumeric), appends it to your LinkShare URL, and sends the viewer onwards.

Bonus points: I prefer to get rid of the ‘php’ extension to make the URL a bit cleaner. Pop the following into your .htaccess file to access ‘download.php’ as just ‘download’:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME}.php -f
RewriteRule . %{REQUEST_FILENAME}.php [L]
</IfModule>

Step 4: Remember the referrer

Now, on the landing page script for your app site (or the site header), pop this in at the very start:

<?php
session_start();
if ( !$_SESSION["original_referer"] ) $_SESSION["original_referer"] = $_SERVER["HTTP_REFERER"];
?>

This stores the original referrer URL in a session variable, to use when we actually link the viewer through to the App Store.

Step 5: Test it

To make sure everything’s working properly, open download.php again, and replace “header” at the bottom with “echo”, so that instead of redirecting the browser, we just print out the URL where we would be redirecting to.

Open your appsite/download URL, and make sure the URL ends with “&u1=appsite“. That’s for direct visitors. Now, click through to your app site from another site, then click your “download” link. You should now see the name of the original site you linked from as the “u1″ parameter at the end of the URL.

Once you’re satisfied that you’re good to go, make sure you replace “echo” with “header” again.

Step 6: Track

Now that you’re ready to track referrals, you can give out your http://yourappsite/download URL as your app’s direct iTunes download link (to reviewers, in your press releases, etc).

You can view a report showing clicks and orders associated with each referrer on the LinkShare page — create an advanced report by clicking the “Advanced Reports” sub-tab, then select your desired date range (I use “Since Last Payment”, and under “Report Type”, select “Signature Activity”. Hit “View Report”, and you’ll see your clicks and sales versus each referrer (“Member ID”, on the report).

Voila! Omnipotence achieved.

Addendum: This technique works for tracking referrers, but if you’re wanting to track the performance of ads (say, with AdMob), you’ll want to use your original LinkShare URL, with a custom “&u1″ signature parameter. As ad platforms like AdMob link directly (and don’t, as far as I know, send a referer parameter), this script won’t pick up that it’s from your ad platform.

Addendum 2: LinkShare’s reports don’t distinguish between products, so if you’ve multiple apps, you might want to add a prefix to your signature parameter to tell ‘em apart. You could, say, replace that header("Location: ".$linkshare_url."&u1=".$signature); line with something like header("Location: ".$linkshare_url."&u1=myapp".$signature);.