The widespread use of intelligent devices and the development of mobile networks have led to the increasing popularity of live-streaming services worldwide. In addition to video and audio transmissions, a wide range of media content is also sent to audiences, such as player statistics for sports streams and subtitles for live news. However, due to the diverse transmission process between live streams and other media content, synchronizing them has become a significant challenge. Unfortunately, existing commercial solutions are not universal, requiring specific server cloud services or CDNs and limiting users’ free choices of web infrastructures. To address this issue, we propose a lightweight and universal solution called LSync, which inserts a series of audio signals containing metadata into the original audio stream. Based on the embedded metadata, a well-designed timeline-synchronizing solution helps to synchronize the information stream to the live stream. It brings no modifications to the original live broadcast process and thus fits prevalent live broadcast infrastructures. Evaluations show that the proposed solution reduces the signal processing delay to around 5% of an audio buffer length in mobile phones and ensures real-time signal processing. It achieves a channel utilization of more than 150 bps/kHz in a specific configuration, greatly outperforming recent works. Furthermore, the proposed synchronization mechanism reaches a precision of 24.84 ms on average, which matches people’s viewing habits.