If you’ve ever faced issues where UTM parameters are stripped from URLs during redirects on a WP Engine-hosted site, you’re not alone. Recently, a client encountered this exact problem, and after some investigation, the root cause was identified and resolved. Here’s how the issue was addressed and how you can fix it too.
The Issue: UTM Parameters Being Stripped
It was observed that when certain URLs containing UTM parameters were accessed, they were redirected, and the UTM parameters were stripped in the process. This behavior was inconsistent—sometimes the parameters would be preserved, other times they would not. The inconsistency led us to suspect a caching issue within the WP Engine environment.
The Setup
- Hosting: WP Engine
- Caching Layers: WP Engine server caching, Cloudflare
- Issue: UTM parameters were being stripped from URLs during redirects, particularly when WP Engine’s caching was involved.
Investigation Process
To diagnose the issue, we tested the behavior of different URLs in various environments:
- With UTM Parameters: URLs like
https://example.com/tuition/program-pricing/?utm_medium=organicsocial&utm_source=facebook&utm_campaign=wpeblog&utm_contentwere often stripped of their query strings when redirected. - With Non-UTM Parameters: Custom parameters like
?nocache=trueworked perfectly, even through redirects.
Key Observations:
- Testing in Incognito Mode and Logged Out: The issue was consistent when tested in incognito mode and when logged out, but the URLs worked fine when logged in. This indicated that the problem was likely related to caching, as logged-in sessions typically bypass caching layers.
- HTTP Header Inspection: By inspecting the HTTP headers during these tests, we noticed the
X-Cacheheader from WP Engine, which indicated whether a response was served from the cache (X-Cache: HIT). This confirmed that the caching layer was likely responsible for stripping the UTM parameters during the redirect.
The Solution: Cache Exclusions in WP Engine
After working with WP Engine support, it was determined that the server-side caching was indeed the culprit. WP Engine’s caching system was aggressively handling URLs with UTM parameters in a way that stripped these parameters during redirects.
The fix involved the following steps:
- Contact WP Engine Support: WP Engine support was contacted, and the issue was explained, with specific examples of URLs where UTM parameters were being stripped. It’s important to note that caching exclusions must be added by WP Engine support and cannot be added by the client directly.
- Implement Cache Exclusions: WP Engine added exclusions for the UTM parameters in their caching system. This ensured that any URL containing these parameters would bypass the cache, preventing the parameters from being stripped.Here’s a screenshot of the cache exclusions that were added:Exclusions Added:
arg: utm_mediumarg: utm_sourcearg: utm_campaignarg: utm_content- Other custom parameters as needed
- Testing: After the exclusions were implemented, the URLs were tested again in various environments (logged in, logged out, incognito mode) to ensure the issue was resolved.
Outcome
With these cache exclusions in place, the UTM parameters were preserved across all redirects, regardless of the caching layer involved. This solution ensured that the client’s marketing efforts and tracking capabilities were not compromised.
Key Takeaways
- Caching Can Be Tricky: Caching systems, especially those at the server level, can sometimes behave unpredictably with certain query strings. UTM parameters are often affected, so it’s crucial to ensure that they’re handled correctly.
- Inspect HTTP Headers: When diagnosing similar issues, inspecting HTTP headers can provide valuable insights. Look for cache-related headers like
X-Cacheto determine if the issue is related to caching. - Work with Your Host: If you encounter issues like this, don’t hesitate to work closely with your hosting provider. They can adjust server configurations and caching rules to suit your needs. In particular, remember that caching exclusions must be added by WP Engine support.
- Implement Cache Exclusions: As was done here, implementing cache exclusions for specific query strings can resolve issues where parameters are stripped during redirects.
Final Thoughts
If you’re hosting on WP Engine and face similar issues with UTM parameters being stripped, the solution may lie in the caching settings. By adding the necessary cache exclusions through WP Engine support, you can ensure that URLs work as expected, preserving all critical parameters. Leave a comment below, if this worked for you.