An Expert Advisor is the code that decides when to trade. The input set is the list of numbers you hand that code before it starts — lot size, stop distance, take-profit, grid spacing, the hours it is allowed to work. Change the set and you change the strategy, even though the EA file on disk stays identical. Two traders can run the same well-known EA and get opposite results for one plain reason: they are not running the same settings.
What an input set is
When you drag an EA onto a chart, MT4 opens the Inputs tab. Every row there is a parameter the developer chose to expose — risk per trade, maximum spread, take-profit in pips, a magic number so the EA only touches its own orders. A .set file is a saved snapshot of those rows. You export one with Save in the Inputs tab and load it back with Load, so a tested configuration moves between charts, terminals or machines without you retyping forty values and getting one wrong.
Why the set matters as much as the EA
The code fixes the logic; the set fixes the risk. A cautious set might risk 0.5% a trade with a 2% daily cap. An aggressive set of the same EA might risk 5% and add to losers on top. Same file, very different odds of surviving a bad week. When a vendor advertises "the EA that made 400% last year", the part that made the 400% — and the part that decides your drawdown — is the set. That is usually the part kept back, or tuned to flatter one backtest.
A worked example
Take a grid EA on a £5,000 account. Set A opens 0.01 lots, steps every 30 pips and caps at five open trades. Set B opens 0.05 lots, steps every 10 pips and has no cap. On a quiet week the two look identical and each makes around £40. On a trending week that runs against the grid, Set A closes down about £120 and survives. Set B stacks fifteen positions, the floating loss runs past £3,000, and the account sits one margin call from zero. The EA did nothing different. The set did all of it.
Where sets go wrong
- Values tuned to one broker's spread, then run on a broker whose spread is twice as wide.
- A set optimised on EURUSD pasted onto GBPJPY because "it's the same EA".
- Two EAs sharing a magic number, so each closes the other's trades.
- The default set shipped with an EA, which is often a demo showcase and not the configuration anyone tested for live money.
A .set file with no note of the broker, pair, timeframe and date it was tested on is a set you cannot trust. The numbers only mean something next to the conditions that produced them.
The Karnek note
Karnek reads what your EA actually does on the live account — the trades, the lot sizes, the timing — straight from the terminal, read-only. It cannot change an input, load a set or place a trade. It shows you the behaviour your current set is producing, which is the only version that matters once real money is on the line.
Written and reviewed by the Karnek Research team. Last updated August 2026.
Educational content only - not financial advice. Past performance does not predict future results. Trading carries significant risk.