A question I often get asked is, “Do Google Analytics filters apply retroactively?” In other words, people want to know if they turn on a filter, will it apply to historical data or only apply to data after the filter was applied?
The answer is simple: No, Google Analytics filters do not apply retroactively. They only apply to data gathered after the filter is applied.
Like many folks, you might be puzzled about what a filter does in Google Analytics. The simplest definition is:
Filters allow you to limit and modify the data included in a view.
For example, you can use filters to exclude traffic from particular IP addresses, focus on a specific subdomain or directory, or convert dynamic page URLs into readable text strings.
Filters permanently alter your data based on the criteria specified. For example, I use a filter to convert all page paths to lowercase, so that the pages /blog and /BLOG would show up as the same page: /blog.
There is no way to undo the changes made by a filter, so it’s important to know exactly what it will do to your data before applying it. It’s a good idea to have a test analytics account for testing filters. Because they permanently alter your data, it’s essential to make sure they’re working correctly before applying them to your live data.
For a safer option to temporarily alter your data, consider creating a segment. Think of a segment as analyzing a subset of your data, such as only viewing traffic on a website when the users came from an email. Segments can be created on the fly, and don’t permanently change anything. Deactivate the segment and the data reverts to normal.
Learn more about segments here.