AI-Powered Error & Log Explainer – No Signup Needed

...

The Error & Log Explainer helps you quickly understand any stack trace or server log. Paste your logs, click Explain, and get the root cause with exact steps to fix it. For simple issues, it even generates a fixed version of your code. Everything runs in your browser with no signup or login required.

Do not get lost. Hit Ctrl+D on Windows or Command+D on Mac to bookmark this tool for instant access.

How To Use The Tool The Right Way

1. Paste the stack trace or logs into the first box
2. Paste the exact function or config related to the error into the second box if you have it
3. Pick a runtime if Auto Detect guesses wrong
4. Click Explain and apply the Fix Now steps in your editor
5. Run the Next Checks steps to confirm the fix

Keep pastes focused. One incident at a time. You will get faster answers and cleaner changes.

Example Walkthrough: Node.js Stack Trace

Input:

TypeError: Cannot read properties of undefined (reading 'length')
    at formatUsers (/app/users.js:42:19)
    at /app/server.js:18:9
    at processTicksAndRejections (node:internal/process/task_queues:95:5)

Related code:

function formatUsers(users){
  const count = users.length
  return `${count} users`
}

What the tool returns:

Summary:
The error occurs because the function formatUsers tries to read the length property of an undefined variable users at /app/users.js line 42.

Root Cause:
The users argument passed to formatUsers is undefined, so accessing users.length throws a TypeError.

Key Errors:
1. formatUsers function in /app/users.js at line 42 accesses users.length without checking if users is defined.
2. The caller in /app/server.js at line 18 passes an undefined or missing users argument to formatUsers.

Fix Now:
- Add a check in formatUsers to ensure users is defined and is an array before accessing length.
- Provide a default empty array if users is undefined.
- Review the caller in server.js to ensure users is properly passed.
- Add input validation or default parameters to prevent undefined inputs.
- Test with valid and undefined users inputs to confirm no error.

Updated Code:
function formatUsers(users = []) {
  const count = users.length;
  return ${count} users;
}

Next Checks:
Run the server and invoke the code path that calls formatUsers with and without users data; verify no TypeError in logs and correct user count output.

This is boring which is exactly what you want in production. Boring fixes are safe and fast.

Example Walkthrough: Python Traceback

Input:

ValueError: invalid literal for int() with base 10: '12.5'
  File "/app/price.py", line 9, in parse_price
    cents = int(value) * 100

Related code:

def parse_price(value):
    cents = int(value) * 100
    return cents

Output:

Summary:
The code breaks when trying to convert a string representing a decimal number (e.g., '12.5') to an integer using int() in the parseprice function at line 9 in price.py.

Root Cause:
int() cannot parse strings containing decimal points; it only accepts whole numbers without special characters.

Key Errors:
1. parseprice function in price.py line 9: int(value) fails on decimal strings like '12.5'.

Fix Now:
- Replace int(value) with float(value) to handle decimal strings.
- Multiply the float result by 100 to convert dollars to cents.
- Convert the final result to int to get an integer number of cents.
- Add error handling to catch invalid inputs if needed.
- Test with various inputs including integers and decimals.

Updated Code:
def parseprice(value):
    cents = int(float(value)  100)
    return cents

Next Checks:
Run unit tests with inputs like '12', '12.5', and invalid strings to confirm no ValueError occurs and correct cent values are returned. Check logs for absence of conversion errors.

Example Walkthrough: Nginx Error Log

Input:

[error] 14#14: *112 open() "/usr/share/nginx/html/api" failed (2: No such file or directory), client: 10.0.0.3, request: "GET /api HTTP/1.1"

Output:

Summary:
Nginx is failing to open the path "/usr/share/nginx/html/api" because the directory or file does not exist on the server.

Root Cause:
The requested resource "/api" is missing from the Nginx document root, causing open() to fail with "No such file or directory."

Key Errors:
open() "/usr/share/nginx/html/api" failed (2: No such file or directory) - Nginx error log

Fix Now:
- Verify if the "/usr/share/nginx/html/api" directory or file should exist.
- If missing, create the required directory or file at that path.
- Check Nginx configuration for correct root and location directives.
- Reload or restart Nginx after changes.
- Confirm permissions allow Nginx to access the path.

Next Checks:
Check Nginx error logs for absence of the open() error after restart and test accessing "/api" endpoint to confirm it serves correctly.

Best Practices For Faster Fixes

• Paste the smallest logs that still show the failure
• Include the function or config that the trace references
• Run the Fix Now steps one by one and retest after each change
• Add a quick unit test when the fix stabilizes
• Keep a copy of the exact error for future regression checks

When To Use Each Output Style

Choose Concise during an incident. You get minimal text and fast steps. Choose Verbose when you want more context for a postmortem or a learning session. You can switch styles without losing your pastes since there is no storage in the tool.

How This Fits Into Your Daily Workflow

When an error shows up you paste the trace and move straight to action. You do not scroll forums for an hour. You fix the line, run the quick checks, and commit. The next pull request focuses on design choices, not on typos in variable names.

Students and junior engineers get the same benefit. They learn the pattern of reading a trace and mapping it to a fix. Over time they rely on the tool less because the pattern is in their head.

Supported Runtimes And Errors

• Node.js with common TypeError, ReferenceError, fetch failures, JSON parse errors
• Python with ValueError, TypeError, KeyError, ImportError, traceback parsing
• Java with NullPointerException, SQL exceptions, HTTP client exceptions
• C Sharp with NullReferenceException and common IO errors
• Go with panic and module import errors
• PHP with undefined index, fatal error, and PDO exceptions
• Rust with borrow checker errors and Result handling mistakes
• SQL with syntax errors, missing columns, and permission issues
• Nginx with open() failed and proxy misrouting
• Docker with port binding errors and missing networks

This is not a full list. If you paste text that looks like an error the tool will try to map it to a cause and a fix.

More Questions About This Tool

Real World Checklists You Can Reuse

For Node.js errors

• Verify input types at the boundary
• Convert string numbers up front
• Add guards before reading length or properties
• Use try and catch around JSON parse and network calls
• Log the error message and the function name

For Python errors

• Validate None and empty strings before parsing
• Use float before int when values may have decimals
• Catch ValueError around casts
• Print the function name and parameters for failing paths
• Add small tests for each branch

For SQL errors

• Confirm table and column names in production
• Quote identifiers only if your schema was created with quotes
• Return only the columns your code reads
• Use parameterized queries
• Add a migration test in CI

For HTTP and Nginx

• Separate static file locations from API routes
• Test each route with curl
• Log upstream status codes
• Keep a minimal default location to avoid path confusion
• Reload after changes and verify with a simple request

How To Get The Most From Updated Code

If the tool includes Updated Code it means the fix is small. Paste it into a branch. Run the quick checks. Commit. If the change touches multiple files you will not get Updated Code because that would be risky. You will get steps instead. That is on purpose to keep you safe.

Troubleshooting The Tool

If Auto Detect picks the wrong runtime switch it in the menu and run again. If the output looks noisy trim your logs to the lines that show the failure and rerun. If the fix fails double check imports or environment variables. Logs can mislead when they include messages from previous requests. Keep the paste focused on the single incident.

Developer’s Note

We hope our AI-powered error & log explainer helped streamline your task. At CodeForGeek, we are constantly developing intelligent tools to boost developer productivity.

• Explore: Check our full suite of free developer tools here.
• Improve: Have feedback or a feature request? Email us at [email protected]. We value user suggestions and act on them.
• Bookmark: Keep CodeForGeek handy for your next project — press Ctrl+D on Windows or Command+D on Mac to bookmark our site.