A Guide to Understanding Regex Differences in Google Analytics 4 and Universal Analytics

As we navigate the ever-evolving world of analytics, transitioning from Universal Analytics (UA) to Google Analytics 4 (GA4) brings about a shift in features and functionalities. One crucial aspect to consider is the behavior of regular expressions (regex) in these two platforms. In this comprehensive guide, we'll explore the intricacies of regex behavior and provide clear examples to highlight the disparities between GA4 and UA.

Matching Behavior: Taking a Closer Look

UA's Approach:

In UA, regular expressions often work by finding patterns within larger text. Imagine you're looking for the term "example." The regex pattern `example` would locate this term within strings like "sample example" or "example123."

GA4's Approach:

However, in GA4, regex patterns seek an exact match by default. To mirror UA's behavior of pattern discovery, you'd introduce the `.*` wildcard. Using the pattern `.*example.*` in GA4 allows you to find the term "example" within various contexts, much like UA's approach.

Delimiters: Full String vs. Partial Matches

UA's Usual Handling:

UA usually identifies patterns within strings even if they're not complete matches. The regex pattern `example` would recognize instances where the term "example" is present.

GA4's Perspective:

On the flip side, GA4 considers regex patterns as requiring an exact match. To replicate UA's partial matching, you'd encompass the pattern with the `.*` wildcard. For instance, `.*example.*` in GA4 extends its reach to match patterns as UA would.

Case Sensitivity: The Case Puzzle

UA's Flexible Case Handling:

In UA, regex isn't concerned with letter case by default. The pattern `example` would account for various letter cases, such as "Example," "eXaMpLe," and more.

GA4's Default Case Approach:

In contrast, GA4's regex treats letter case as significant unless specified otherwise. To adopt UA's flexible case handling in GA4, you'd introduce the `(?i)` flag. For example, `(?i)example` would encompass various letter cases as UA does.

Advanced Flags: The Advanced Toolbox

UA's Toolbox of Advanced Features:

UA's regex is equipped with various advanced flags for fine-tuning patterns. The `(?m)` flag enables matching across multiple lines, while `(?s)` makes dots include newline characters.

GA4's Simplified Approach:

In GA4, the support for advanced flags is more streamlined. Flags like `(?m)` and `(?s)` are not part of GA4's regex toolkit.

Lookahead and Lookbehind: Peering Through Time

UA's Lookahead and Lookbehind Usage:

UA regex introduces two techniques: lookahead (`(?=...)`) and lookbehind (`(?<=...)`). These techniques assist in determining if a pattern is followed by (`(?=...)`) or preceded by (`(?<=...)`) another pattern.

GA4's Lack of Time-Travelling:

However, GA4's regex arena doesn't accommodate these techniques. While UA users benefit from this additional layer of complexity, GA4's regex environment calls for alternative approaches when constructing intricate patterns.

Illustrating the Differences: Detailed Examples for Clarity

To offer visual clarity on these distinctions, let's break down each point with illustrative examples:

Point	Example Pattern (UA)	Example Pattern (GA4)
​Matching Behavior	`example`	`.*example.*`
​Delimiters	`example`	​ `.*example.*`
​Case Sensitivity	`example`	`(?i)example`
Advanced Flags	`(?m)multiline`	`multiline`
Lookahead and Lookbehind	`(?<=prefix)word`	Not supported in GA4

In Conclusion: Navigating Regex in the GA4 Era

As you transition from UA to GA4, comprehending the nuanced differences in regex behavior is key for precise data interpretation. Equipped with our comprehensive examples and explanations, you're well-prepared for a seamless migration. By adapting your regex patterns to the GA4 framework, you'll harness the power of data analytics and confidently navigate the dynamic terrain of Google Analytics 4.