Why Did My Sessions Go Down In Google Analytics?

June 29, 2016

Perhaps the most common question that an analyst receives is “Why did my sessions go down last month?” The question of why sessions increased is not asked with nearly the same frequency, or urgency, but it is equally important. A significant change in sessions, formerly known as visits, usually means that a significant event happened on your site, such as a new marketing campaign, or an error in your Google Analytics implementation. My goal is to help you figure out the cause of a sudden change in sessions!

Most large changes in visit numbers fall into one of the following categories:

  1. Nothing actually happened and everything is normal
  2. Something on your site changed and now Google Analytics is collecting data incorrectly
  3. Traffic actually changed, and Google Analytics is right
  4. Everything is back to normal, after being different the month before

Sanity Check: Nothing Happened and Everything Is Normal

Every site experiences some variation in traffic from month to month. Sometimes a large change in traffic volume is just business as usual. There are a few quick sanity checks you should do before you go down the rabbit-hole of trying to identify causes.

1. Your site traffic has high variability

Look at the monthly traffic for your site over the past year or so. See if large swings up or down are normal.

Follow-up: The Wikipedia article on Standard Deviation.

2. Seasonality

Many businesses are cyclic. Most retail sites have larger volumes of traffic in December because of the holidays. A flower shop might have more traffic around Valentine’s Day and Mother’s Day, while people are more interested in tax preparation services near early April.

Follow-up: Change your Date Comparison range to the same month from last year.

3. It’s February

Many sites receive around 10% fewer visits in February than the month before. This is because February has around 10% fewer days than the month before (except during leap years).


If none of the above situations apply, then it’s time to begin investigating your site traffic. The first thing you should do is plot your daily traffic over the past month, and look at whether your traffic change took place in a single day, over the course of a few days, or gradually over the course of a month.

Instantaneous Change: Something Broke Google Analytics.


If Google Analytics broke, then there is usually one specific change that caused it to break. This change could be a code push on your site, or a configuration change in Google Analytics, or an interaction with third-party code on your site. Whatever the cause, it is usually an instantaneous change with no build-up or tapering. Look at your daily traffic graph and see if you can identify a single day where something changed.


  • Graph multiple metrics side-by-side. A true change in traffic will affect all site metrics, but a technical problem will often change visits but not pageviews, or bounce rate but not visits.
  • Segment by device category or browser. Some technical issues are browser-specific.
  • Look at the change history of Google Analytics or Google Tag Manager for recent tag or configuration changes on the date of the change.

An Actual Increase in Traffic

Sometimes when Google Analytics reports a significant change in the number of visits to your site, that’s because there was actually a significant change to the number of visits to your site. While technology issues happen suddenly, site traffic changes usually take a longer time. Marketing efforts have their impact over the course of a few days, while natural site growth is a slower process.

1. Sudden Change with Tapering: Marketing Efforts



Like changes to your website, paid marketing efforts like paid search campaigns and email blasts have a specific go-live date. However, marketing campaigns usually spread their impact out over several days. Long-term campaigns like banner ads and paid search campaigns usually take a few days to saturate, and continue to optimize after launch. Single events like email blasts will stay in an inbox and be opened a few days later. A sudden change, followed by a stabilization period, usually signals a marketing campaign.


  • Campaign reports.
  • Talk to your marketing team

2. Gradual Change: Natural Traffic Change


A change in site traffic can be caused by natural growth or decline, or it can be the result of a change in marketing efforts. Natural growth is usually a slow, steady process. If the change in site traffic is spread out over a long period of time, then it is usually a result of a change in general awareness of your site.


  • Acquisition reports: Source/Medium, and Keyword if available.
  • Social Media reporting

Things Are Back to Normal

If the traffic reported on your site for one month is different than the month before, don’t assume that the previous month was correct and the reported month is the exception. If the previous month was exceptional, then the reported month will look different because it’s returning back to normal from the exceptional state. Sometimes you only find out about an exceptional situation after it goes away, especially if that situation was causing your traffic to go up.

Follow-up: Pull a longer date range and look for the opposite effect in the past.

What Next?

Now that you know what’s actually causing the difference on your site, you can decide what to do about it. If there’s a technical issue, you should fix it. If there’s a marketing change, you need to communicate with your marketing team to let them know what’s going on, but sometimes the answer isn’t as clear-cut as “whatever you did, undo it.” Sometimes you need to wait and see while a campaign builds up, or figure out how to improve a campaign rather than stop it. Oftentimes, the only response is to communicate and educate, so that your stakeholders aren’t surprised when the same change happens again.