MT5 Log Analysis: How to Find EA Errors, Execution Issues, and Order Problems

1. What Is MT5 Log Analysis?

1.1 Definition of MT5 Log Analysis

MT5 mainly outputs the following logs:

• Experts log: EA behavior, Print output, and order processing
• Journal log: Overall MT5 behavior, connections, and server communication

By analyzing these logs, you can clarify the following:

• Why an order did not go through
• Why no entry was made
• Why an error occurred
• What the actual execution conditions were

The key point is that “logs are the facts themselves.”
They are not subjective impressions. They become the only data that proves what actually happened.

1.2 Information You Can Find in Logs

Typical information you can check includes:

• Order processing
  • OrderSend (order submission)
  • OrderCheck (pre-check)
  • execution (execution result)
• Market conditions
  • spread
  • slippage
  • price (Bid / Ask)
• Error information
  • invalid volume
  • not enough money
  • off quotes
• EA internal processing
  • Print logs (debug output)
  • Whether conditional branches were passed

For example, even when no entry is made, logs can identify causes such as:

• The spread was too wide
• The conditions were not met
• The order was rejected

This is fundamentally different from backtesting, where you only look at results.

1.3 Why Log Analysis Matters

The reasons are as follows:

• Backtesting is an ideal environment
  → Real execution and slippage are not reproduced
• Forward testing only shows results
  → You cannot tell why those results occurred
• Logs record the “process”
  → You can trace the issue back to its cause

In other words, the roles are divided like this:

• Backtest: result
• Forward test: real-world result
• Log analysis: cause

In practical work, log analysis is especially necessary in these situations:

• The EA does not run
• The EA enters at a different time than expected
• Profit and loss differ from expectations
• A problem occurs only with a specific broker

If you judge without checking logs, you are likely to reach the wrong conclusion.

Common Mistakes at This Stage

• Assuming the EA is broken without checking logs
• Guessing the cause from the result alone
• Ignoring differences between demo and live environments

Log analysis is a method for removing guesswork.
You must always judge based on facts.

2. Types and Storage Locations of MT5 Logs

2.1 Types of MT5 Logs

The two main logs are:

Experts Log (EA Log)

EA behavior history
Print logs (debug output)
Order processing (OrderSend / OrderCheck)
Logic branch status

→ Check this first when investigating EA issues

Journal Log (Overall Log)

Server connection status
Order results (execution)
Errors (trade error)
Market status (market closed / off quotes)

→ Use this to check communication, broker, and environment issues

2.2 Where Logs Are Stored

How to Open Logs from the GUI (Fastest Route)

1. Open MT5
2. Go to “File” → “Open Data Folder”
3. Move to the following folders

• MQL5/Logs → Experts log
• Logs → Journal log

File Structure

• Experts log MQL5/Logs/YYYYMMDD.log
• Journal log Logs/YYYYMMDD.log

Notes

Logs are separated by date
Older logs may be deleted automatically
They are saved in text format (.log)

2.3 Difference Between Experts and Journal

How to Use Them in Practice

• The EA does not run
  → Experts log
• The order does not go through
  → Check Experts first, then Journal
• Execution looks abnormal (slippage or execution issue)
  → Journal log

Common Mistakes

• Judging an EA problem by looking only at Journal
• Guessing the cause without checking the Experts log
• Checking the wrong date’s log

A very common case is thinking you are checking the log while actually looking at the wrong date.
Always check the log that matches the time of the event.

Why This Structure Exists

MT5 separates roles as follows:

• EA (logic)
• Terminal (execution environment)
• Server (broker)

Logs are separated according to these roles, so
you need to change which log you read depending on the cause.

3. How to Analyze MT5 Logs

3.1 Basic Procedure (Fastest Route)

Follow these steps:

1. Open MT5
2. Display the “Terminal” window (Ctrl+T)
3. Select the “Experts” or “Journal” tab
4. Find the log for the relevant time period
5. Search by keyword with Ctrl+F (error / failed / invalid, etc.)
6. Check the entries before and after the matching log

Example Search Keywords

• error
• failed
• invalid
• reject
• not enough money

Important Point

You cannot identify the cause from only “the line where the error appeared”
Always check the logs before and after it

3.2 How to Check Log Files

Steps

1. In MT5, go to “File” → “Open Data Folder”
2. Move to:
   • Experts log: MQL5/Logs
   • Journal log: Logs
3. Select the log file for the relevant date
4. Open it in a text editor such as Notepad
5. Search with Ctrl+F

Analysis Tips

Filter by time (timestamp)
Check whether the same error repeats
Read the log flow in chronological order

3.3 Efficient Analysis Techniques

Technique 1: Follow the Timeline

All logs are chronological.

Example:

10:00 Condition check
10:00 OrderSend
10:00 error

→ Identify the cause from this flow

Technique 2: Trace Back from the Error

Start the analysis from the error code.

Example:

• invalid volume → invalid lot size
• not enough money → insufficient margin
• off quotes → price cannot be obtained

→ The log immediately before the error usually points to the cause

Technique 3: Use Print Logs

Adding debug output to the EA greatly improves analysis efficiency.

Print("Spread=", SymbolInfoInteger(_Symbol, SYMBOL_SPREAD));
Print("Lot=", lot_size);
Print("Condition=", condition_flag);

This lets you confirm:

• Whether the conditions are met
• Whether variable values are correct
• Whether the logic path is being reached

3.4 Practical Analysis Flow

1. Identify the symptom
   • No entry is made
   • An error appears
   • Profit and loss are off
2. Identify the relevant time
3. Check the Experts log
   • Logic
   • OrderSend
4. Check the Journal log
   • execution
   • Server response
5. Identify the cause from the surrounding logs

Common Mistakes

• Judging from only the error line
• Not adding Print logs
• Ignoring the timeline
• Looking at a different day’s log

Not using Print logs is especially serious.
Because the internal state is invisible, cause identification becomes difficult.

Why This Procedure Is Needed

Logs are not just text. They are a continuous record of causal relationships involving:

• EA decisions
• Market conditions (spread / slippage)
• execution results

Therefore, you need to read logs as a flow, not as isolated lines.

4. How to Read Logs and Understand Their Mechanism

4.1 Basic Log Structure

Typical log format:

2026.04.01 10:00:00.123    Experts    OrderSend request

Components

• Time (timestamp)
  → When it occurred, down to milliseconds
• Module
  → Experts / Journal / Trade, etc.
• Message
  → The actual processing content

Reading Points

• Group consecutive logs with the same timestamp
• Watch for time gaps or delays
• Confirm whether the entries belong to the same EA

4.2 Log Flow for Order Processing

Typical Flow

Print: Condition met
OrderSend request
OrderCheck result
Trade request sent
Execution result

Meaning of Each Step

• Condition met
  → The EA logic passed
• OrderSend
  → Order submission
• OrderCheck
  → Server-side pre-check
• Execution
  → Actual execution result

Analysis Points

No OrderSend → conditions were not met
Failed at OrderCheck → condition or parameter issue
Failed at Execution → server or market condition issue

4.3 How Errors Occur

Error Patterns

1. EA side (logic or parameters)
   • invalid volume
   • invalid stops
2. MT5 side (environment or state)
   • trade context busy
   • no connection
3. Server side (market or broker)
   • off quotes
   • market closed

Example: not enough money

OrderSend request
OrderCheck failed: not enough money

→ Cause: insufficient margin
→ Fix: adjust the lot size

Example: off quotes

Trade request sent
Off quotes

→ Cause: price cannot be obtained
→ Possible factors:

• Sudden spread widening
• Low liquidity
• Server delay

4.4 Reading Causal Relationships from Logs

Steps

1. Identify the final result, such as an error or failure
2. Check the immediately preceding log
3. Confirm the conditions and environment

Concrete Example

10:00:00 OrderSend
10:00:00 OrderCheck
10:00:01 not enough money

→ Result: order failed
→ Immediately before: check was executed
→ Cause: insufficient margin

4.5 Common Misreadings

• Deciding the cause from the error alone
• Ignoring chronological order
• Confusing Experts and Journal
• Not checking Print logs

A particularly common mistake is reversing cause and effect.
Logs must always be read in chronological order.

Why This Mechanism Exists

MT5 processing has the following structure:

• EA (decision)
• Terminal (submission)
• Server (execution)

Because logs record this processing as it happens,
understanding the system flow makes the logs easier to read naturally.

5. Common Errors and Causes

5.1 Common Error List

5.2 Causes and Fixes by Error

invalid volume

Cause:

• The lot size does not match the minimum unit
• Broker restrictions are violated

Fix:

• Use SymbolInfoDouble to get the minimum lot
• Normalize the lot size

double min_lot = SymbolInfoDouble(_Symbol, SYMBOL_VOLUME_MIN);
double lot_step = SymbolInfoDouble(_Symbol, SYMBOL_VOLUME_STEP);
lot = MathMax(min_lot, lot);
lot = NormalizeDouble(lot, 2);

not enough money

Cause:

• Insufficient margin
• Lot size is too large

Fix:

• Lower the lot size
• Check free margin

double margin = AccountInfoDouble(ACCOUNT_FREEMARGIN);

off quotes

Cause:

• Price updates have stopped
• Spread has widened suddenly
• Server delay

Fix:

• Implement retry processing
• Add a spread filter

trade context busy

Cause:

• Order processing overlaps
• Asynchronous processing conflicts

Fix:

• Add a wait between processes

Sleep(100);

invalid stops

Cause:

• SL/TP is too close
• Broker restrictions are violated

Fix:

• Get the minimum stop distance

double stop_level = SymbolInfoInteger(_Symbol, SYMBOL_TRADE_STOPS_LEVEL);

5.3 Steps to Identify the Cause from Logs

Steps

1. Identify the error line
2. Check the previous log
3. Check the following:
   • lot
   • spread
   • slippage
   • execution conditions
4. Check the EA’s conditional branches

Practical Example

OrderSend request
OrderCheck failed: invalid volume

Analysis:

• OrderSend was executed
• OrderCheck failed
• Cause: invalid lot size

5.4 How to Think About Error Analysis in Practice

Important viewpoints:

• Has the spread widened?
• Have execution conditions changed?
• Are there differences between brokers?

Example:

• It works on demo but fails on live
  → execution / slippage may be affecting it

Common Mistakes

• Judging by the error name alone
• Not checking lot size and margin
• Ignoring broker specifications
• Drawing a conclusion from a single log

A common issue is overlooking environment factors.
Always check logs multiple times under multiple conditions.

Why Error Analysis Matters

Errors are not just failures. They are signals that show:

• Logic defects
• Insufficient risk management
• Lack of response to market conditions

Therefore, error analysis is the shortest path to improving an EA.

6. Comparison with Other Methods

6.1 Difference Between Log Analysis and Backtesting

Note

Backtesting is fast and efficient, but it does not accurately reproduce:

• slippage
• execution rejection
• server delay

For this reason, backtesting alone cannot reveal live operation problems.

6.2 Difference Between Log Analysis and Forward Testing

Note

Forward testing does not directly show:

• Why an entry was not made
• Why a loss occurred

→ This is where log analysis becomes necessary.

6.3 How to Use Each Method in Practice

Recommended Flow

1. Backtesting
   → Validate the strategy’s effectiveness
2. Forward testing
   → Check behavior in a real environment
3. Log analysis
   → Identify the cause of problems

Practical Example

Case: the number of entries is low

• Backtest
  → No problem
• Forward test
  → Few entries
• Log analysis
  → Entries are being blocked by the spread filter

→ Cause identified

6.4 Brief Comparison with Other Alternatives

Alternatives

• Trade history
  → Results only
• Chart analysis
  → Visual but ambiguous
• Backtest report
  → Virtual data

→ None of these explains the cause

Common Misunderstandings

• If the backtest is good, there is no problem
• If the forward test is profitable, it is enough
• Logs are only for developers

All of these are insufficient.

In particular, the following can only be checked in a real environment:

• execution
• slippage
• spread

Why Log Analysis Is Necessary

A trading system is built from three elements:

• Logic (EA)
• Market conditions
• Broker specifications

Log analysis is the only method that can make all three visible at the same time.

7. Common Mistakes and Cautions

7.1 Judging Without Checking Logs

Common cases:

• Assuming “the EA does not run = bug”
• Concluding “the order does not go through = broker problem”

In reality, the cause is often:

• Conditions were not met
• Spread restriction
• Lot setting mistake

Fix

Always check logs before judging
At minimum, check the Experts log

7.2 Ignoring the Timeline

Typical Mistake

10:00 error
10:00 OrderSend

→ In reality, the order is OrderSend → error

Fix

Always check timestamps
Read logs with the same timestamp as a group

7.3 Looking Only at the Error

Bad Example

not enough money

→ This alone is not enough

Correct Reading

OrderSend request
OrderCheck
not enough money

→ You can tell the cause is lot size or margin

Fix

Check at least three lines before the error
Read the flow

7.4 Ignoring Differences Between Demo and Live Accounts

Main differences:

• spread (live accounts often vary more)
• slippage (live accounts can experience it)
• execution speed

Common Misunderstanding

• It worked on demo, so it will be the same in production
  → Wrong

Fix

Always check logs from the live account
Design with execution conditions in mind

7.5 Not Using Print Logs

Problems

• You cannot tell whether conditions are met
• You cannot confirm variable values

Recommended Code

Print("Spread=", SymbolInfoInteger(_Symbol, SYMBOL_SPREAD));
Print("Lot=", lot);
Print("Signal=", signal_flag);

Fix

Always output important variables
Add logs before and after conditional branches

7.6 Drawing a Conclusion from a Single Log

Bad Example

Determining the cause from one error

Correct Method

Compare multiple trades
Test at different times
Check with multiple brokers

7.7 Ignoring Broker Specifications

Factors that affect behavior:

• Minimum lot
• Stop level
• execution method
• spread

Fix

Get specifications with SymbolInfo
Validate by broker

Why These Mistakes Happen

Log analysis handles the following at the same time:

• Logic
• Market conditions
• Execution environment

Simple judgment is not enough.

You need the habit of judging from records, not guesses.

8. Practical Use Cases

8.1 Use During EA Development

Main uses:

• Checking conditional branches
• Validating entry decisions
• Checking whether parameters are valid

Concrete Example

Case: no entry is made

Log:

Signal=false
Spread=25

→ Analysis:

• Signal was not triggered
• Excluded by the spread filter

Response

• Review the conditions
• Adjust the acceptable spread value

Basic Development Flow

1. Implement Print logs
2. Run a backtest
3. Check the logs
4. Compare conditions with execution results

Cautions

• Too many logs create noise
• Limit logs to necessary variables

8.2 Use During Forward Operation

Main uses:

• Checking missed entries
• Detecting abnormal execution (slippage / execution)
• Understanding environment changes

Concrete Example

Case: the number of entries decreases

Log:

Spread=40
Condition=true
No trade

→ Analysis:

• The condition is met
• The spread is too wide

→ Conclusion: market environment changed

Operational Check Items

• Average spread
• execution success rate
• Error frequency

Practical Points

• Check logs daily
• Analyze immediately when abnormal behavior appears
• Check long-term trends as well

8.3 Commercial Decisions

Reasons:

• They reflect actual execution conditions
• They include slippage and delay
• They reflect broker differences

Example Decision Criteria

• Low error rate
• Stable execution success rate
• No major breakdown under spread conditions

Bad Decisions

• Judging only from backtesting
• Judging only from a demo account

8.4 Log Analysis as Risk Management

Risks it can detect:

• Excessive lot size (money management error)
• Worsening execution (increased slippage)
• Market environment change (spread widening)

Practical Uses

• Detecting outliers
• Identifying drawdown causes
• Deciding when to stop a strategy

8.5 Why Log Analysis Affects Expected Value

Trading results consist of:

• Logic
• execution
• Market conditions

Because log analysis can validate all three at the same time, it:

• Reduces uncertainty
• Improves reproducibility

As a result, it reduces variation in expected value.

Common Practical Mistakes

• Checking logs only after a problem occurs
• Not checking live account logs
• Testing under only one condition

→ This is not enough for risk management.

Practical Summary

• Check logs continuously
• Analyze problems immediately
• Use the real environment as the standard

9. FAQ

9.1 Where Are MT5 Logs Located?

Steps:

1. Open MT5
2. Go to “File” → “Open Data Folder”
3. Check the following:
   • MQL5/Logs (Experts log)
   • Logs (Journal log)

9.2 What Is the Difference Between Experts and Journal?

• Experts
  → Logic, Print, OrderSend
• Journal
  → execution, communication, errors

For EA issues, the basic rule is to check Experts first.

9.3 Is Log Analysis Required?

Reasons:

• It is the only way to identify the cause
• It can detect problems that backtesting cannot show
• It is needed to confirm reproducibility

9.4 Why Does the EA Not Run Even Though No Error Appears?

Check these points:

• spread restriction
• Time filter
• Signal condition

Using Print logs helps identify the cause.

9.5 Is Backtesting Alone Insufficient?

Missing elements include:

• slippage
• execution
• Server delay

→ These must be supplemented with log analysis.

9.6 How Long Are Logs Stored?

Countermeasures:

• Save necessary logs manually
• Back them up regularly

9.7 Should I Use Print Logs?

Example:

Print("Spread=", SymbolInfoInteger(_Symbol, SYMBOL_SPREAD));
Print("Lot=", lot);
Print("Condition=", condition_flag);

→ You can make the internal state visible

9.8 Can Log Analysis Alone Solve Problems?

Additional factors:

• Broker specifications
• execution conditions
• Market conditions

Accuracy improves when you judge by combining these factors.