Why Redirect URLs May Include Long Tracking Parameters

When running redirect-based template or experience tests, you may notice a long query parameter such as vsly-redirected-event appended to the destination URL. This parameter passes the tracking context needed to associate the visit with the correct experience, variant, and redirect event.

 What these parameters are used for

• Experience attribution: associates the page visit with the originating test, template, or use case.
• Variant identification: indicates which experience variant the visitor was sent to.
• Event continuity: preserves the redirect event details so reporting remains accurate after navigation.
• Analytics support: works similarly to common campaign parameters such as UTM tags, where information is passed in the URL for downstream tracking.
  
  

 Example redirect URL:

https://www.example-store.com/products/sample-product?view=test-template&vsly-redirected-from=example-experience-id-example-variant-id&vsly-redirected-event=eyJ0eXBlIjoiUkVESVJFQ1RfRVZFTlQiLCJ0cyI6MTc3NzkyNTM4NDAwMCwicGF5bG9hZCI6eyJzaWQiOiJleGFtcGxlLXNlc3Npb24taWQiLCJ1c2VyIjp7ImFub255bW91c19pZCI6ImV4YW1wbGUtYW5vbnl tb3VzLWlkIn0sImV4cGVyaWVuY2UiOiJleGFtcGxlLWV4cGVyaWVuY2UtaWQiLCJ2YXJpYW50IjoiZXhhbXBsZS12YXJpYW50LWlkIiwiY2xpY2tJZCI6InJlZGlyZWN0In0sIm9wdGlvbnMiOnsiaXNSZWRpcmVjdCI6dHJ1ZX19

Why the parameter can look unusually long

The vsly-redirected-event value is typically an encoded payload rather than a short identifier. It may include metadata such as event type, session identifiers, anonymous user information, experience IDs, variant IDs, and redirect flags.

Can the tracking parameters be hidden from the customer?

In a standard redirect implementation, no. The parameters must be included in the URL so the destination page receives the data required for tracking and attribution.

This works similarly to visible marketing parameters such as UTMs: if the destination page needs the tracking context, it must receive data it can read during or immediately after the redirect.