See exactly what the JavaScript SDK is doing — flag evaluations, context payloads, streaming connections, and every event in between.
The extension adds a LaunchPad panel to Chrome DevTools. It uses the DevTools Network API, so it captures requests with full HAR timing, response sizes, and headers — no monkey-patching needed.
chrome://extensions and enable Developer modeThe extension works immediately on the current page — no reload required. It sees every request the SDK makes, including those that already happened before you opened the panel.
The bookmarklet injects an event viewer panel directly into any page. It works in Chrome, Firefox, Safari, and Edge — no extension install needed. It intercepts LD SDK traffic by monkey-patching fetch, XMLHttpRequest, and EventSource, and renders its UI in a Shadow DOM so it won't interfere with the host page's styles.
Drag this to your bookmarks bar:
LD Event ViewerDrag the button above to your bookmarks bar, then click it on any page running the LD JS SDK.
Or copy the bookmark URL manually:
To capture all SDK traffic from the very first request — including the streaming connection and initial identify — use a DOM breakpoint to pause the page before any scripts run, then click your bookmarklet while paused:
<head> element → Break on → subtree modifications<head>The breakpoint persists across reloads. To remove it, right-click <head> and uncheck subtree modifications.
In Firefox: Inspector → right-click <head> → Break on… → Subtree Modification, then the same flow.
If you can edit the page's HTML, drop this in during development. Since the tag loads with the page, all SDK requests are captured automatically — no DevTools needed:
Just click the bookmarklet on any page with the LD SDK already running. The viewer will capture any future SDK traffic — streaming updates, identify calls, custom events — but won't see requests that already happened.
To remove the viewer from the current page, run in the console:
LDJSSDK.remove()