What is a Set File (.set) in MetaTrader?

A set file (.set) is a small text file that stores an Expert Advisor's input parameters - lot size, risk settings, indicator periods, magic number, all of it. Instead of retyping dozens of values every time you attach an EA, you load the .set file and every input snaps to the saved configuration. Vendors also use set files to distribute recommended settings for their EAs.

What a set file contains

Only the Inputs - the parameters you see on the Inputs tab of the EA's properties window. It does not contain the EA itself, the chart, the symbol, or the Common-tab permissions like Allow Algo Trading. You still need the EA installed (see installing in MT5 / MT4) and attached to the right chart.

How to save a set file

1. Attach the EA to a chart and open its properties window.
2. Adjust the inputs to the configuration you want to keep.
3. On the Inputs tab, click Save, give the file a clear name, and store it somewhere you will find again.

How to load a set file

1. Attach the EA to a chart (or open the properties of one already attached).
2. On the Inputs tab, click Load and select the .set file.
3. Check the values populated correctly, confirm the Common-tab trading permission is ticked, and press OK.

Set files also work in the Strategy Tester - you can load the same configuration you trade live into a test run, which keeps your backtests honest about what you are actually running.

Why set files matter more than they look

• Reproducibility. "Which settings was I running in March?" is answerable only if you saved them. Save a dated set file every time you change anything.
• Safe experimentation. Save your current configuration before tinkering. If the experiment disappoints, one click restores the known-good state.
• Migration. Moving to a new PC or VPS? Copy the EA plus its set file and you are back in business - no reconstructing settings from memory.
• Sharing and support. When something misbehaves, sending the vendor your set file shows them exactly what you were running.

Common mistakes

• Mixing platforms and versions. A set file only fits the EA (and version) it was saved from. Loading it into a different EA or an updated version with renamed inputs can silently leave parameters at defaults - always eyeball the values after loading.
• Assuming the set file carries permissions. Allow Algo Trading / Allow live trading is not stored in it. If the EA sits idle after loading, run the not-taking-trades checklist.
• Trusting an optimised set file blindly. A set file produced by aggressive optimisation is often a snapshot of curve-fitting - tuned to the past, fragile in the future. Before trading someone's "best settings", understand out-of-sample testing and overfitting.
• One set file, no versioning. Overwriting the same file destroys your history. Date-stamp the filenames.

Settings are part of the system

An EA and its settings are inseparable - the same code with different inputs is effectively a different strategy. That is why systems exported from Nebula ship with their validated configuration baked in: the settings that passed testing are the settings you deploy, rather than a blank EA plus a folder of mystery set files.

Trading carries a high level of risk. Nothing here is financial advice; past performance does not predict future results.