Debug VWO in Chrome DevTools

What VWO traffic looks like

VWO's SmartCode fetches settings, buckets the visitor, then beacons back, with the assignment state persisted client-side in cookies.

Endpoint pattern

Settings and library from dev.visualwebsiteoptimizer.com (typically a js_visitor_settings.php or settings request keyed by account ID), with library assets also served from the d5phz18u4wuww.cloudfront.net CDN; tracking beacons go back to dev.visualwebsiteoptimizer.com; a slow settings response here is what users experience as the anti-flicker blank flash

Transport

Classic pixel-style requests on older SmartCode; newer versions send batched event calls with vwo_-prefixed event names for variation shown and goal conversions

Key parameters

a account ID · exp experiment ID · c combination/variation ID

Cookies

_vwo_uuid visitor identity · per-experiment _vis_opt_exp_<id>_combi records the locked-in variation: the beacon tells you what fired now, the cookie tells you what was assigned earlier

Debugging VWO with Event Watcher

• Detects VWO from its request URLs and names and categorizes every call in the live stream.
• No dedicated VWO parser: parsed query and body parameters make account, experiment, and combination IDs readable directly, rather than decoded sections.
• The per-event cookies panel surfaces the _vis_opt_* assignment cookies.
• The consent check runs on every request.

VWO and consent

The extension checks VWO against functional consent. VWO's beacons carry a persistent visitor UUID, so firing before the CMP grant means an identifier left the browser pre-consent. Those events are marked pre-consent and added to the violations counter.

Implementations that load SmartCode unconditionally (for anti-flicker reasons) but claim to suppress tracking are worth verifying: the settings request may be fine, but watch whether tracking beacons hold off until consent.

Common debugging scenarios

• Visitor not entering the test. Check for the settings request, then look for a beacon carrying the expected experiment ID. The _vis_opt_exp_<id>_combi cookie in the cookies section shows the stored assignment.
• Goal conversions missing. Filter to VWO in the stream and confirm a conversion beacon fires on the goal page or click; compare its experiment/goal parameters against the campaign setup.
• Anti-flicker blank flash. SmartCode hides the page (typically body, or configured elements) until settings arrive or a tolerance timeout expires. Script Tree shows whether a tag manager injected SmartCode, which delays settings and stretches the hide window.
• Pre-consent bucketing. Use the consent badges to see whether assignment beacons fire before the CMP grant.
• Multiple testing tools colliding. Pivot Grouped view by Tool to see VWO next to AB Tasty or Optimizely when two tools fight over the same pages.