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Headline Testing network calls

Use browser DevTools to verify Headline Testing is functioning correctly or to troubleshoot issues with a test.

Prerequisites

How to view network calls

  1. Open browser DevTools (F12 or right-click > Inspect).
  2. Select the Network tab.
  3. Filter by “parsely” to isolate relevant requests.
  4. Load or refresh the page containing the headline test.

Check network calls during a test

When a headline test is functioning correctly, the browser makes several network calls. The first call, on the homepage, loads the vip-experiments.js script. Without this call, the test does not function.

Browser DevTools Network tab filtered by parsely, showing the vip-experiments.js script request highlighted with a red annotation indicating the script is being loaded

Next, still on the homepage, a tr?experiment_id call fires with an impression event type.

Browser DevTools Network tab showing a tr?experiment_id request selected, with the Payload panel displaying event_type as impression

After a visitor clicks the article being tested, another tr?experiment_id call fires with a click event type.

Browser DevTools Network tab showing a tr?experiment_id request selected, with the Payload panel displaying event_type as click

Troubleshooting

  • The vip-experiments.js script does not load: Verify the headline test is active and that the script has been correctly added. For SPA or pages loading dynamically, enable the enableLiveUpdates option. See Install Headline Testing: Live Updates for configuration details.
  • The impression or click events do not fire: Confirm the vip-experiments.js script has been loaded.

Last updated: February 11, 2026