Fiddler Everywhere doesn’t alter the content of WebSocket messages. If the message is in a recognisable compressed format, Fiddler will attempt to automatically decompress it. However, if it can’t determine the format, the message will be shown in its raw form, which can appear unreadable or garbled. From what you’re seeing, it’s likely that Fiddler doesn’t automatically decode them. You can use the raw data and try to additionally define the format or decode.