MT4 error 4200: Object already exists (ERR_OBJECT_ALREADY_EXISTS)

ObjectCreate() was called with a name that is already on the chart. Check with ObjectFind() first, or move the existing object.

4200ERR_OBJECT_ALREADY_EXISTS

After a fixSafe to retry?

Not a tradeCould it have executed?

What it means

You see this code in GetLastError() in MQL4, raised inside the terminal.

Chart objects need unique names. Creating one with a name already in use fails with 4200.

It is not a trade error, but it is one of the most common errors in MT4 logs, because programs often redraw lines on every tick.

Common causes

ObjectCreate() on every tick with the same name.
Objects left on the chart from a previous run.

How to fix it

Call ObjectFind() first, and move the object with ObjectMove() or ObjectSet() if it exists.
Delete your objects in OnDeinit().

Example in MQL4:

void DrawEntry(double entryPrice)
{
   string name = "entry_line";
   if(ObjectFind(0, name) < 0)
      ObjectCreate(0, name, OBJ_HLINE, 0, 0, entryPrice);   // first time only
   else
      ObjectMove(0, name, 0, 0, entryPrice);                // later: move it
}

void OnDeinit(const int reason) { ObjectDelete(0, "entry_line"); }

Is it safe to retry?

Not as a create. Move or delete the existing object.

Could the order have executed?

Not a trade code.

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