14 Aug 2025
“Is Decompiling EX4 Files Illegal? Legal Risks & Best Practices”
Is Decompiling EX4 Files Illegal? Legal Risks & Best Practices
Meta Description:
Wondering if decompiling EX4 files is legal? Learn the laws, risks, and best practices for working with MetaTrader 4 EX4 files the right way.
Introduction
If you trade on MetaTrader 4 (MT4), you’ve probably encountered EX4 files — the compiled version of Expert Advisors (EAs), indicators, and scripts.
Sometimes, traders want to convert EX4 back into MQ4 (the editable source code) — either to recover lost code, make changes, or study how a system works. But here’s the big question: Is this legal?
The short answer: It depends — on ownership, permissions, and local laws. In this blog, we’ll break down when decompiling EX4 files is legal, when it’s not, and the safest best practices.
EX4 vs MQ4 — A Quick Refresher
• MQ4 File – The human-readable source code written in MQL4.
• EX4 File – The compiled binary format that MT4 executes but hides from human reading.
Decompiling is the reverse-engineering process to convert EX4 back into MQ4.
When Decompiling EX4 Files is Legal
✅ You own the code
If you wrote the MQ4 file yourself and lost it, you can legally attempt to recover it.
✅ You have written permission
If the original developer has explicitly authorized you to decompile or provided a license that allows it.
✅ It’s open-source or free-to-use
Some EAs and indicators are distributed under licenses that allow modification, even if you only have the EX4 version.
When Decompiling EX4 Files is Illegal
❌ You don’t own the intellectual property
Recovering someone else’s code without permission is copyright infringement in most countries.
❌ You bought the EX4 but not the source rights
Purchasing an EA or indicator doesn’t mean you can reverse-engineer it — most licenses forbid it.
❌ You intend to redistribute or sell the decompiled code
Selling or sharing a decompiled version of someone else’s work is a serious legal violation.
Legal Risks of Unauthorized Decompilation
1. Copyright Infringement – The developer can sue for damages.
2. Breach of Contract – Violating MetaTrader’s EULA or a software license agreement.
3. Marketplace Bans – Trading platforms like MQL5.com and Forex Factory ban users for promoting or requesting illegal decompilation.
4. Criminal Charges – In some countries, reverse-engineering without permission can be prosecuted as a criminal offense.
Best Practices for Handling EX4 Files
If you need to recover code legally, follow these safe steps:
1. Check Your License Agreement
Always read the EA or indicator’s terms. Some licenses allow modifications, but most prohibit reverse-engineering.
2. Contact the Original Developer
The simplest route is often asking the creator for the MQ4 file — especially if you can prove you bought or commissioned it.
3. Search Your Backups
You might have the MQ4 file saved on your old hard drives, cloud storage, or even email attachments.
4. Hire a Verified Developer
If you legally own the rights, you can hire a trusted MQL4 developer to rebuild or recover your code.
5. Keep a Secure Archive
Once you have the MQ4 source, store it safely — both locally and in the cloud.
Why the Temptation is Risky
Even if you’re convinced no one will find out, here’s why you should think twice:
• Decompiled code is often messy and hard to work with.
• Online decompiler tools are frequently scams that install malware.
• MetaQuotes actively updates MT4 to make decompilation harder and detect unauthorized use.
Conclusion
Decompiling EX4 files is not automatically illegal — but it’s a gray area with strict boundaries. If you own the intellectual property or have written permission, you’re safe. If not, you’re risking lawsuits, bans, and even criminal charges.
The best practice? Always work with code you legally own and use legitimate recovery methods. It keeps you compliant, secure, and respected in the trading community.
