I was looking at some code on our site today when I noticed a suspicious error in the JavaScript console. The code was trying to open a websocket on localhost. Does anyone know where this sort of code would be coming from.
Topic summary
JavaScript console shows attempts to open a WebSocket to localhost, raising concern about suspicious code. A screenshot of the console error is referenced.
- Likely source: Facebook Pixel (Facebook’s analytics/tracking script). A developer community thread reports the same error, suggesting it’s widespread and likely an issue on Facebook’s side rather than site-specific code.
- Technical notes: A WebSocket is a persistent browser connection; “localhost” targets the user’s own machine. There’s no definitive explanation for why Pixel uses a WebSocket, but it’s probably related to real-time analytics.
Outcomes and status:
- No concrete fix or action identified in the discussion.
- The cause is attributed to Facebook Pixel, with the error presumed to be on Facebook’s end.
- Open question remains: the exact reason for the localhost WebSocket usage. The issue appears ongoing without a confirmed resolution.
This seems to be connected to the Facebook Pixel and is probably an error on their side. Here you can find a thread about more people complaining about the same error: https://developers.facebook.com/community/threads/317050484803752/ , regarding the question why they use a websocket there is no clear answer, but it’s probably used for Realtime Analytics
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