Error & solution reference

Fix the error. Move on.

Plain-English explanations and working fixes for 100 common error messages — from Windows codes and blue screens to HTTP status codes, databases, Python, JavaScript, Docker, Git and SSL.

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Every page below takes a single error message, explains in plain English what it means, lists the most common causes, and gives step-by-step fixes that actually work. Pick a category or a specific error to get started.

Windows

0x80070005 — Access is denied

0x80070002 — The system cannot find the file specified

0xC0000005 — Access violation

Windows Update error 0x80070422

Windows Update error 0x80072EFD

Windows Update error 0x80244019

0x80070057 — The parameter is incorrect

Blue Screen (BSOD)

IRQL_NOT_LESS_OR_EQUAL

Blue Screen (BSOD)

KERNEL_SECURITY_CHECK_FAILURE

Blue Screen (BSOD)

DPC_WATCHDOG_VIOLATION

Blue Screen (BSOD)

CRITICAL_PROCESS_DIED

Blue Screen (BSOD)

UNMOUNTABLE_BOOT_VOLUME

Blue Screen (BSOD)

HTTP status codes

HTTP status codes

500 Internal Server Error

HTTP status codes

502 Bad Gateway

HTTP status codes

503 Service Unavailable

HTTP status codes

504 Gateway Timeout

HTTP status codes

HTTP status codes

401 Unauthorized

HTTP status codes

Browser & network

ERR_CONNECTION_REFUSED

Browser & network

ERR_CONNECTION_RESET

Browser & network

ERR_CONNECTION_TIMED_OUT

Browser & network

ERR_SSL_PROTOCOL_ERROR

Browser & network

DNS_PROBE_FINISHED_NXDOMAIN

Browser & network

ERR_CERT_AUTHORITY_INVALID

Browser & network

ERR_NAME_NOT_RESOLVED

Browser & network

ERR_ADDRESS_UNREACHABLE

Browser & network

ERR_TOO_MANY_REDIRECTS

Browser & network

ERR_QUIC_PROTOCOL_ERROR

Browser & network

SSL_ERROR_BAD_CERT_DOMAIN

Browser & network

Databases

MySQL error 1064 — You have an error in your SQL syntax

MySQL error 1045 — Access denied for user

MySQL error 2002 — Can't connect to local MySQL server

MySQL error 2006 — MySQL server has gone away

MySQL error 1049 — Unknown database

MySQL error 1146 — Table doesn't exist

MySQL error 1054 — Unknown column

PostgreSQL — permission denied for relation

PostgreSQL — relation does not exist

ORA-12154 — TNS:could not resolve the connect identifier

Python

ModuleNotFoundError: No module named 'x'

ImportError: cannot import name 'x'

IndentationError: unexpected indent

TypeError: 'NoneType' object is not subscriptable

SyntaxError: invalid syntax

NameError: name 'x' is not defined

TypeError: 'x' object is not callable

ValueError: invalid literal for int()

FileNotFoundError: [Errno 2] No such file or directory

JavaScript & Node

TypeError: Cannot read properties of undefined

JavaScript & Node

TypeError: x is not a function

JavaScript & Node

npm ERR! ERESOLVE unable to resolve dependency tree

JavaScript & Node

npm ERR! ENOENT: no such file or directory

JavaScript & Node

ReferenceError: x is not defined

JavaScript & Node

Uncaught TypeError

JavaScript & Node

TypeError: Cannot read properties of null

JavaScript & Node

npm ERR! EACCES: permission denied

JavaScript & Node

npm ERR! code ELIFECYCLE

JavaScript & Node

Error: Cannot find module 'x'

JavaScript & Node

JavaScript heap out of memory

JavaScript & Node

TypeError: Cannot set properties of undefined

JavaScript & Node

Docker

Cannot connect to the Docker daemon

Docker — no space left on device

Docker — port is already allocated

Docker — pull access denied for image

Servers & ports

nginx — bind() to 0.0.0.0:80 failed

Servers & ports

EACCES: permission denied

Servers & ports

EADDRINUSE: address already in use

Servers & ports

connect() failed (111: Connection refused)

Servers & ports

Git

fatal: refusing to merge unrelated histories

! [rejected] — non-fast-forward

fatal: not a git repository

error: Your local changes would be overwritten

CONFLICT (content): Merge conflict

fatal: Authentication failed

SSL & certificates

SSL certificate verify failed

SSL & certificates

SSL handshake failed

SSL & certificates

unable to get local issuer certificate

SSL & certificates

Let's Encrypt rate limit exceeded

SSL & certificates

Certbot DNS authentication failed

SSL & certificates

Self-signed certificate error

SSL & certificates

PHP & WordPress

Error establishing a database connection

PHP & WordPress

Fatal error: Allowed memory size exhausted

PHP & WordPress

Parse error: syntax error, unexpected

PHP & WordPress

WordPress white screen of death

PHP & WordPress

Warning: Undefined array key

PHP & WordPress

HTTP error when uploading image

PHP & WordPress

PHP 500 Internal Server Error

PHP & WordPress

Mixed content warning

PHP & WordPress

Linux & system

No space left on device

[Errno 13] Permission denied

Segmentation fault (core dumped)

Out of memory: Killed process

curl: (60) SSL certificate problem

curl: (7) Failed to connect

ssh: connect to host — Connection refused

WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED

Java

java.lang.OutOfMemoryError: Java heap space

java.lang.NullPointerException