Cross-broker (cross-platform) copy trading: symbol suffixes, lot sizes and latency
Cross-broker copy trading means the master and copy accounts are MT5 accounts at different brokers. Using NB Copy Engine as the example, this guide explains symbol matching, lot conversion and why speed and fill prices can differ.
Niubang editorial · Updated
What cross-broker copy trading is
Cross-broker copy trading means the master account and the copy account are held at different brokers, for example the master at broker A and the copy account at broker B. Niubang describes NB Copy Engine as a “Cross-platform · Millisecond-level copy trading EA”, and cross-platform means exactly this: MT5 accounts at different brokers can copy each other. Copying only works between MT5 accounts; MT4 and MT5 cannot copy each other.
Connecting a copy account needs only the login, trading password and server name, not broker back-office (Manager) access, so the two accounts do not have to be at the same broker. Across brokers, three things need handling: symbol names, lot specifications, and differences in execution speed and fill prices.
How symbol names and suffixes are matched
Brokers often name the same instrument differently, most commonly by adding a suffix: XAUUSD, XAUUSD.m, XAUUSD-ECN, XAUUSD#. NB Copy Engine matches in three steps: first, an exactly matching symbol in the copy account; second, symbol aliases Niubang configures for the two broker servers; third, comparing names with suffixes removed, so XAUUSD.m and XAUUSD-ECN both map to XAUUSD.
The third step has one limit: it is used only when a single candidate remains after removing suffixes. If several symbols in the copy account could match, the system does not guess, and that symbol is not copied.
Symbols with completely different names are never treated as the same automatically. Some brokers call gold GOLD and others XAUUSD; that case needs an alias first, so contact support. When copying starts, the cloud runs a symbol pre-check, and a symbol that cannot be matched shows in red as “品种不可执行” (symbol cannot be executed) instead of being forced through.
How lot sizes are converted
Copy lots = master lots × multiplier, with the multiplier between 0.01 and 100. The result is rounded to 0.01 lot: a 0.30-lot master trade with a 0.5 multiplier becomes 0.15 lots. A new position below the broker's minimum lot is placed at the minimum lot, so with a very small multiplier the copied position can be larger than the proportional amount.
Contract specifications can differ between brokers, such as the contract size per lot, the minimum lot and the lot step, so the same lot size may not mean the same exposure at two brokers. Check both sides in the MT5 symbol specification before you start. A new multiplier applies only to later signals; copied positions that are already open are not changed.
Why speed and fill prices can differ
Speed: Copying is triggered the moment the master trade fills, with millisecond-level order placement in the cloud. Actual execution speed depends on broker servers, the network and liquidity.
Fill prices: copy accounts use market orders, filled at the copy broker's price at that moment. Brokers differ in quotes, spreads and liquidity, so fill prices can differ from the master, more so in fast markets. Copying does not mean identical returns.
What is copied: opening, closing, partial closing and stop-loss or take-profit changes. Pending orders themselves are not copied; a master pending order is copied once it fills and becomes a position. Copying mirrors individual positions, with no special handling for netting accounts.
A checklist before you start
One, confirm both accounts are MT5. Two, find the matching symbol in the copy account and check its name, contract specification and minimum lot. Three, set the multiplier for your account size, keeping the minimum lot in mind. Four, after starting, read the pre-check result; if you see “品种不可执行” (symbol cannot be executed), contact support to configure an alias. Five, once running, compare a few master and copy fills to confirm direction and size match your expectations.
Copy trading involves risk, and a strategy's past performance does not guarantee future returns.