System message (WhatsApp)
A line WhatsApp writes into the chat itself — someone joined, a call happened, the encryption notice — with no sender and no place in a message count.
A chat export mixes two very different kinds of line: things a person wrote, and notes WhatsApp itself inserts to record events — someone was added to the group, the security code changed, a voice call started. These system lines have no sender, because nobody sent them; they’re closer to a log entry than a message. Any statistic built from an export has to filter them out specifically, or a group with a lot of people joining and leaving ends up looking far more talkative than it actually was.
Example
A group chat export with 585 system lines out of thousands of total lines might record every member join, every name change, and the standard end-to-end encryption notice — none of it a real message from a real conversation.
Frequently asked questions
Does the group name itself come from a system message?+
Often, yes — a "changed the group name to..." system line is one of the few places a group’s actual name can be recovered from, which is why a group recap can usually show the real name rather than just a headcount.
Why does WhatsApp put these in the same file as real messages at all?+
Because the export is meant to be a full, readable record of everything that happened in the chat, in order — a human reading the raw file benefits from seeing "Alex joined the group" in context, even though a statistics tool has to treat it differently.