Tracking the performance of your social campaigns is critical in maximizing your success. But the fact is that your Google Analytics data and your Facebook data will never match entirely.

Why is this?

The only way to accurately measure your Facebook data is through Facebook reporting itself - here are some key reporting notes on the variations between the two, why they exist, and what you need to watch for.

1. Cross Device Conversions
In this day and age, people use multiple devices throughout the user journey before a purchase is made - it takes multiple touch points, and this happens across multiple devices. 

For example, suppose you’re out and about and start browsing on your mobile device. You click on an ad but don’t convert, but then later that day, you’re sitting at your desktop computer and you decide to jump onto that company’s website to buy the product you saw earlier. Google Analytics would fail to attribute that conversion back to the initial click on your mobile device, and would subsequently under-report your results.

Facebook, on the other hand, has the unique ability to track conversions back to users instead of cookies. This means you can track the same user across all devices as long as they’re logged into their Facebook account. By comparison, Google Analytics relies on cookies, meaning all the tracking happens exactly on the browser where the cookie was dropped.

2. Impressions and Clicks
Google Analytics uses cookies to track users on a website, and doesn’t have the ability to track impressions like Facebook. If cookies aren’t enabled, you won’t be able to track those users through GA.

With Google Analytics, it’s considered a conversion when a user clicks the intended link within the ad, whereas with Facebook, a user can click any portion of the ad, convert, and still be tracked as a conversion.

If a user clears their cookies, all of that data will remain in Google Analytics. In Facebook, however, this data is cleared from your custom audiences. It’s also good to note that Google Analytics back-dates data, while Facebook collects the data from the day your audiences are set up.

3. Clicks vs. Sessions
This one is always a cause for concern with marketers:

“Wait, my clicks in Facebook don’t match my sessions reported in Google Analytics? Why?”
There are several reasons for this discrepancy.

If a user clicks your Facebook post more than once in a 30-minute window, Google Analytics only tracks this as one session. Conversely, Facebook considers this as more than one click. (i.e., one Google Analytics session and two Facebook clicks).
If a user clicks your Facebook post and visits your website, becomes inactive for more than 30 minutes, and then re-engages with your site after 30 minutes, Google will records two separate sessions. Facebook reports only the single click. In this case, one Facebook click equals two sessions.
If a user accidentally clicks your Facebook ad but jumps off quickly, Google Analytics will most likely not have had the chance to record this click, since the page hadn’t loaded fully.

4. UTM Parameters
Google Analyti

cs uses referrer URLs to credit conversions back to ads. Facebook users browse Facebook using ‘https’ instead of ‘http’. So, if a user clicks an ad in Facebook and leaves to convert on an http website, the user can’t be recorded since they have left a secure environment. This, again, will lead to under-reporting of conversions.

5. Multiple Conversions
This is an important one to note - Google Analytics only allows a one-per-click attribution, meaning only one conversion is counted regardless of the number of conversions that actually happened. If a user saw or clicked an ad and converted multiple times, Facebook attributes multiple conversions to the ad last clicked or viewed.

6. Attribution Window
Facebook conversion measurement attributes conversions based on a 24-hour view and 28-day click-through window - so, any comparison you do against other tracking data must compare exactly the same attribution window. Google Analytics uses the last interaction model, which attributes 100% of the conversion value to the last channel the customer interacted with before buying or converting.To update your attribution window in Facebook, click Customize Columns and choose the window that best suits your needs.

7. Conversion Date
Facebook reports on the time of a view or click of the conversion, whereas third party tracking tools often report on the time of conversion.

8. Ad Blocker Software
Your conversion pixel may not fire if the user has an ad blocker installed in the browser. This will cause undercounting conversions, so the number may be lower than your internal data.

These are some of the key reasons you're seeing discrepancies in your Facebook Insights and Google Analytics data, and it's important to understand these variations to ensure your data is correct and that you're tracking the correct info. When you do note any discrepancies, make sure you trace back the details and confirm the various source points, using this list as a reference, to help ensure the validity of your info.