diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..3844bb3
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+# Composer
+/composer.lock
+/vendor/
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..5c86d38
--- /dev/null
+++ b/README.md
@@ -0,0 +1,31 @@
+# EasyCodingStandard configurations for Contao
+
+[![](https://img.shields.io/packagist/v/contao/easy-coding-standard.svg?style=flat-square)](https://packagist.org/packages/contao/easy-coding-standard)
+[![](https://img.shields.io/packagist/dt/contao/easy-coding-standard.svg?style=flat-square)](https://packagist.org/packages/contao/easy-coding-standard)
+
+This package includes the EasyCodingStandard configurations for [Contao][1].
+
+## Installation
+
+You can install the package with Composer:
+
+```
+composer require contao/easy-coding-standard
+```
+
+## Usage
+
+```
+vendor/bin/ecs check *-bundle/src *-bundle/tests --config vendor/bin/contao/easy-coding-standard/config/default.yaml
+```
+
+## License
+
+Contao is licensed under the terms of the LGPLv3.
+
+## Getting support
+
+Visit the [support page][2] to learn about the available support options.
+
+[1]: https://contao.org
+[2]: https://contao.org/en/support.html
diff --git a/composer.json b/composer.json
new file mode 100644
index 0000000..59c6c91
--- /dev/null
+++ b/composer.json
@@ -0,0 +1,22 @@
+{
+    "name": "contao/easy-coding-standard",
+    "type": "library",
+    "description": "EasyCodingStandard configurations for Contao",
+    "license": "LGPL-3.0-or-later",
+    "authors": [
+        {
+            "name": "Leo Feyer",
+            "homepage": "https://github.com/leofeyer"
+        }
+    ],
+    "require": {
+        "php": "^7.1",
+        "symplify/coding-standard": "^7.1",
+        "symplify/easy-coding-standard": "^7.1"
+    },
+    "autoload": {
+        "psr-4": {
+            "Contao\\EasyCodingStandard\\": "src/"
+        }
+    }
+}
diff --git a/config/default.yaml b/config/default.yaml
new file mode 100644
index 0000000..1aa3f61
--- /dev/null
+++ b/config/default.yaml
@@ -0,0 +1,12 @@
+imports:
+    - { resource: set/contao.yaml }
+
+parameters:
+    exclude_files:
+        - '*/Resources/*'
+
+    skip:
+        Symplify\CodingStandard\Sniffs\Naming\AbstractClassNameSniff:
+            - '*TestCase.php'
+
+    cache_directory: '%sys_get_temp_dir%/ecs_default_cache'
diff --git a/config/legacy.yaml b/config/legacy.yaml
new file mode 100644
index 0000000..2e2f75a
--- /dev/null
+++ b/config/legacy.yaml
@@ -0,0 +1,77 @@
+imports:
+    - { resource: set/contao.yaml }
+
+parameters:
+    exclude_files:
+        - '*/languages/*'
+        - '*/templates/*'
+        - '*/themes/*'
+
+    skip:
+        PhpCsFixer\Fixer\ArrayNotation\TrailingCommaInMultilineArrayFixer: ~
+        PhpCsFixer\Fixer\ClassNotation\OrderedClassElementsFixer: ~
+        PhpCsFixer\Fixer\ClassNotation\VisibilityRequiredFixer:  ~
+        PhpCsFixer\Fixer\ControlStructure\YodaStyleFixer: ~
+        PhpCsFixer\Fixer\FunctionNotation\NoSpacesAfterFunctionNameFixer: ~
+        PhpCsFixer\Fixer\FunctionNotation\VoidReturnFixer: ~
+        PhpCsFixer\Fixer\Operator\BinaryOperatorSpacesFixer: ~
+        PhpCsFixer\Fixer\Operator\IncrementStyleFixer: ~
+        PhpCsFixer\Fixer\Phpdoc\NoSuperfluousPhpdocTagsFixer: ~ # FIXME: remove
+        PhpCsFixer\Fixer\Phpdoc\PhpdocOrderFixer: ~
+        PhpCsFixer\Fixer\Phpdoc\PhpdocScalarFixer: ~
+        PhpCsFixer\Fixer\Phpdoc\PhpdocSeparationFixer: ~
+        PhpCsFixer\Fixer\Phpdoc\PhpdocSummaryFixer: ~
+        PhpCsFixer\Fixer\Phpdoc\PhpdocToCommentFixer: ~
+        PhpCsFixer\Fixer\ReturnNotation\ReturnAssignmentFixer: ~
+        PhpCsFixer\Fixer\Semicolon\MultilineWhitespaceBeforeSemicolonsFixer: ~
+        PhpCsFixer\Fixer\Strict\DeclareStrictTypesFixer: ~
+        PhpCsFixer\Fixer\Strict\StrictComparisonFixer: ~
+        PhpCsFixer\Fixer\Strict\StrictParamFixer: ~
+        PhpCsFixer\Fixer\StringNotation\SingleQuoteFixer: ~
+        SlevomatCodingStandard\Sniffs\PHP\UselessParenthesesSniff: ~
+        SlevomatCodingStandard\Sniffs\Variables\UselessVariableSniff: ~
+        Symplify\CodingStandard\Sniffs\Naming\AbstractClassNameSniff: ~
+        Symplify\CodingStandard\Sniffs\Naming\InterfaceNameSniff: ~
+        Symplify\CodingStandard\Sniffs\Naming\TraitNameSniff: ~
+
+    indentation: tab
+    cache_directory: '%sys_get_temp_dir%/ecs_legacy_cache'
+
+services:
+    PhpCsFixer\Fixer\ArrayNotation\ArraySyntaxFixer:
+        syntax: long
+
+    PhpCsFixer\Fixer\Basic\BracesFixer:
+        allow_single_line_closure: true
+        position_after_anonymous_constructs: next
+        position_after_control_structures: next
+
+    PhpCsFixer\Fixer\ListNotation\ListSyntaxFixer:
+        syntax: long
+
+    PhpCsFixer\Fixer\Operator\ConcatSpaceFixer:
+        spacing: one
+
+    # Remove the "case" statement (see contao.yaml)
+    PhpCsFixer\Fixer\Whitespace\BlankLineBeforeStatementFixer:
+        statements:
+            - declare
+            - default
+            - do
+            - for
+            - foreach
+            - if
+            - return
+            - switch
+            - throw
+            - try
+            - while
+
+    # Remove the "throws" token (see symfony.yaml)
+    PhpCsFixer\Fixer\Whitespace\NoExtraBlankLinesFixer:
+        tokens:
+            - curly_brace_block
+            - extra
+            - parenthesis_brace_block
+            - square_brace_block
+            - use
diff --git a/config/set/contao.yaml b/config/set/contao.yaml
new file mode 100644
index 0000000..5fea9de
--- /dev/null
+++ b/config/set/contao.yaml
@@ -0,0 +1,137 @@
+imports:
+    - { resource: '%vendor_dir%/symplify/easy-coding-standard/config/set/php70.yaml' }
+    - { resource: '%vendor_dir%/symplify/easy-coding-standard/config/set/php71.yaml' }
+    - { resource: '%vendor_dir%/symplify/easy-coding-standard/config/set/common.yaml' }
+    - { resource: '%vendor_dir%/symplify/easy-coding-standard/config/set/clean-code.yaml' }
+    - { resource: '%vendor_dir%/symplify/easy-coding-standard/config/set/dead-code.yaml' }
+    - { resource: '%vendor_dir%/symplify/easy-coding-standard/config/set/symfony.yaml' }
+    - { resource: '%vendor_dir%/symplify/easy-coding-standard/config/set/symfony-risky.yaml' }
+
+parameters:
+    skip:
+        # We allow assignments in conditions (see common.yaml)
+        PHP_CodeSniffer\Standards\Generic\Sniffs\CodeAnalysis\AssignmentInConditionSniff: ~
+
+        # We do not want explicit variables (see common.yaml)
+        PhpCsFixer\Fixer\LanguageConstruct\ExplicitIndirectVariableFixer: ~
+        PhpCsFixer\Fixer\StringNotation\ExplicitStringVariableFixer: ~
+
+        # We do not want a space after the ! operator (see common.yaml)
+        PhpCsFixer\Fixer\Operator\NotOperatorWithSuccessorSpaceFixer: ~
+
+        # We allow assertEquals() to compare objects in configuration tests (see phpunit.yaml)
+        PhpCsFixer\Fixer\PhpUnit\PhpUnitStrictFixer:
+            - '*/*BundleTest.php'
+            - '*/*ExtensionTest.php'
+
+        # The method chaining identation fixer does not work for the Symfony configuration tree
+        PhpCsFixer\Fixer\Whitespace\MethodChainingIndentationFixer:
+            - '*/Configuration.php'
+            - '*/src/Resources/contao/*' # FIXME: remove?
+
+        # We do not require null default values to be nullable (see php71.yaml)
+        SlevomatCodingStandard\Sniffs\TypeHints\NullableTypeForNullDefaultValueSniff: ~
+
+        # Do not report unused variables in foreach loops etc. (see clean-code.yaml)
+        SlevomatCodingStandard\Sniffs\Variables\UnusedVariableSniff: ~ # FIXME: remove?
+
+services:
+    PhpCsFixer\Fixer\Comment\HeaderCommentFixer:
+        header: "This file is part of Contao.\n\n(c) Leo Feyer\n\n@license LGPL-3.0-or-later"
+
+    PhpCsFixer\Fixer\ConstantNotation\NativeConstantInvocationFixer:
+        scope: namespaced
+        fix_built_in: false
+        include:
+            - DIRECTORY_SEPARATOR
+            - PHP_SAPI
+            - PHP_VERSION_ID
+
+    PhpCsFixer\Fixer\FunctionNotation\FopenFlagsFixer:
+        b_mode: false
+
+    PhpCsFixer\Fixer\FunctionNotation\NativeFunctionInvocationFixer:
+        scope: namespaced
+        strict: true
+        include:
+            - '@@compiler_optimized'
+
+    # We do not enforce blank lines before "break", "continue" and "yield"
+    PhpCsFixer\Fixer\Whitespace\BlankLineBeforeStatementFixer:
+        statements:
+            - case
+            - declare
+            - default
+            - do
+            - for
+            - foreach
+            - if
+            - return
+            - switch
+            - throw
+            - try
+            - while
+
+    PhpCsFixer\Fixer\PhpUnit\PhpUnitTestCaseStaticMethodCallsFixer:
+        call_type: this
+
+    # Add fixers from PHP-CS-Fixer
+    PhpCsFixer\Fixer\Alias\PowToExponentiationFixer: ~
+    PhpCsFixer\Fixer\Alias\SetTypeToCastFixer: ~
+    PhpCsFixer\Fixer\Casing\LowercaseStaticReferenceFixer: ~
+    PhpCsFixer\Fixer\Casing\MagicMethodCasingFixer: ~
+    PhpCsFixer\Fixer\Casing\NativeFunctionTypeDeclarationCasingFixer: ~
+    PhpCsFixer\Fixer\CastNotation\NoUnsetCastFixer: ~
+    PhpCsFixer\Fixer\ClassNotation\NoNullPropertyInitializationFixer: ~
+    PhpCsFixer\Fixer\Comment\MultilineCommentOpeningClosingFixer: ~
+    PhpCsFixer\Fixer\ControlStructure\IncludeFixer: ~
+    PhpCsFixer\Fixer\ControlStructure\NoAlternativeSyntaxFixer: ~
+    PhpCsFixer\Fixer\ControlStructure\NoSuperfluousElseifFixer: ~
+    PhpCsFixer\Fixer\FunctionNotation\CombineNestedDirnameFixer: ~
+    PhpCsFixer\Fixer\FunctionNotation\FopenFlagOrderFixer: ~
+    PhpCsFixer\Fixer\FunctionNotation\ImplodeCallFixer: ~
+    PhpCsFixer\Fixer\FunctionNotation\NoUnreachableDefaultArgumentValueFixer: ~
+    PhpCsFixer\Fixer\FunctionNotation\SingleLineThrowFixer: ~
+    PhpCsFixer\Fixer\FunctionNotation\StaticLambdaFixer: ~
+    PhpCsFixer\Fixer\Import\FullyQualifiedStrictTypesFixer: ~
+    PhpCsFixer\Fixer\Import\SingleImportPerStatementFixer: ~
+    PhpCsFixer\Fixer\LanguageConstruct\CombineConsecutiveIssetsFixer: ~
+    PhpCsFixer\Fixer\LanguageConstruct\CombineConsecutiveUnsetsFixer: ~
+    PhpCsFixer\Fixer\LanguageConstruct\ErrorSuppressionFixer: ~
+    PhpCsFixer\Fixer\LanguageConstruct\NoUnsetOnPropertyFixer: ~
+    PhpCsFixer\Fixer\Operator\LogicalOperatorsFixer: ~
+    PhpCsFixer\Fixer\Phpdoc\AlignMultilineCommentFixer: ~
+    PhpCsFixer\Fixer\Phpdoc\PhpdocOrderFixer: ~
+    PhpCsFixer\Fixer\Phpdoc\PhpdocVarAnnotationCorrectOrderFixer: ~
+    PhpCsFixer\Fixer\PhpTag\LinebreakAfterOpeningTagFixer: ~
+    PhpCsFixer\Fixer\PhpTag\NoShortEchoTagFixer: ~
+    PhpCsFixer\Fixer\PhpUnit\PhpUnitDedicateAssertInternalTypeFixer: ~
+    PhpCsFixer\Fixer\PhpUnit\PhpUnitExpectationFixer: ~
+    PhpCsFixer\Fixer\PhpUnit\PhpUnitMockFixer: ~
+    PhpCsFixer\Fixer\PhpUnit\PhpUnitMockShortWillReturnFixer: ~
+    PhpCsFixer\Fixer\PhpUnit\PhpUnitNamespacedFixer: ~
+    PhpCsFixer\Fixer\PhpUnit\PhpUnitNoExpectationAnnotationFixer: ~
+    PhpCsFixer\Fixer\PhpUnit\PhpUnitOrderedCoversFixer: ~
+    PhpCsFixer\Fixer\ReturnNotation\NoUselessReturnFixer: ~
+    PhpCsFixer\Fixer\Semicolon\MultilineWhitespaceBeforeSemicolonsFixer: ~
+    PhpCsFixer\Fixer\StringNotation\EscapeImplicitBackslashesFixer: ~
+    PhpCsFixer\Fixer\StringNotation\HeredocToNowdocFixer: ~
+    PhpCsFixer\Fixer\StringNotation\NoBinaryStringFixer: ~
+    PhpCsFixer\Fixer\StringNotation\SimpleToComplexStringVariableFixer: ~
+    PhpCsFixer\Fixer\StringNotation\StringLineEndingFixer: ~
+
+    # Add fixers and sniffs from https://github.com/Symplify/CodingStandard
+    Symplify\CodingStandard\Fixer\Commenting\ParamReturnAndVarTagMalformsFixer: ~
+    Symplify\CodingStandard\Fixer\Commenting\RemoveEmptyDocBlockFixer: ~
+    Symplify\CodingStandard\Fixer\Commenting\RemoveSuperfluousDocBlockWhitespaceFixer: ~
+    Symplify\CodingStandard\Fixer\ControlStructure\RequireFollowedByAbsolutePathFixer: ~
+    Symplify\CodingStandard\Sniffs\CleanCode\ForbiddenParentClassSniff: ~
+    Symplify\CodingStandard\Sniffs\Commenting\AnnotationTypeExistsSniff: ~
+    Symplify\CodingStandard\Sniffs\Debug\DebugFunctionCallSniff: ~
+    Symplify\CodingStandard\Sniffs\Naming\AbstractClassNameSniff: ~
+    Symplify\CodingStandard\Sniffs\Naming\InterfaceNameSniff: ~
+    Symplify\CodingStandard\Sniffs\Naming\TraitNameSniff: ~
+
+    # Add custom fixers
+    Contao\EasyCodingStandard\Fixer\SingleLineConfigureCommandFixer: ~
+    Contao\EasyCodingStandard\Sniffs\SetDefinitionCommandSniff: ~
diff --git a/config/template.yaml b/config/template.yaml
new file mode 100644
index 0000000..c710b00
--- /dev/null
+++ b/config/template.yaml
@@ -0,0 +1,21 @@
+imports:
+    - { resource: set/contao.yaml }
+
+parameters:
+    file_extensions:
+        - html5
+
+    skip:
+        PhpCsFixer\Fixer\ClassNotation\VisibilityRequiredFixer:  ~
+        PhpCsFixer\Fixer\Comment\HeaderCommentFixer: ~
+        PhpCsFixer\Fixer\ControlStructure\NoAlternativeSyntaxFixer: ~
+        PhpCsFixer\Fixer\FunctionNotation\VoidReturnFixer: ~
+        PhpCsFixer\Fixer\PhpTag\BlankLineAfterOpeningTagFixer: ~
+        PhpCsFixer\Fixer\PhpTag\LinebreakAfterOpeningTagFixer: ~
+        PhpCsFixer\Fixer\PhpTag\NoShortEchoTagFixer: ~
+        PhpCsFixer\Fixer\Semicolon\SemicolonAfterInstructionFixer: ~
+        PhpCsFixer\Fixer\Strict\DeclareStrictTypesFixer: ~
+        PhpCsFixer\Fixer\Strict\StrictComparisonFixer: ~
+        PhpCsFixer\Fixer\Strict\StrictParamFixer: ~
+
+    cache_directory: '%sys_get_temp_dir%/ecs_template_cache'
diff --git a/src/Fixer/SingleLineConfigureCommandFixer.php b/src/Fixer/SingleLineConfigureCommandFixer.php
new file mode 100644
index 0000000..a5ee1a1
--- /dev/null
+++ b/src/Fixer/SingleLineConfigureCommandFixer.php
@@ -0,0 +1,90 @@
+<?php
+
+namespace Contao\EasyCodingStandard\Fixer;
+
+use PhpCsFixer\AbstractFixer;
+use PhpCsFixer\FixerDefinition\CodeSample;
+use PhpCsFixer\FixerDefinition\FixerDefinition;
+use PhpCsFixer\Tokenizer\Tokens;
+
+final class SingleLineConfigureCommandFixer extends AbstractFixer
+{
+    public function getDefinition(): FixerDefinition
+    {
+        return new FixerDefinition(
+            'Defining command arguments and options must be done in single line.',
+            [
+                new CodeSample(
+                    '<?php
+
+use Symfony\Component\Console\Command\Command;
+
+class SomeCommand extends Command
+{
+    protected function configure(): void
+    {
+        $this
+            ->addOption(
+                "bundles",
+                null,
+                InputOption::VALUE_NONE,
+                "List all bundles or the bundle configuration of the given plugin"
+            );
+    }
+}
+'
+                ),
+            ]
+        );
+    }
+
+    public function isCandidate(Tokens $tokens): bool
+    {
+        return $tokens->isAllTokenKindsFound([T_CLASS, T_FUNCTION, T_OBJECT_OPERATOR]);
+    }
+
+    protected function applyFix(\SplFileInfo $file, Tokens $tokens): void
+    {
+        for ($index = 1, $count = \count($tokens); $index < $count; ++$index) {
+            switch (true) {
+                case $tokens[$index]->isGivenKind(T_CLASS):
+                    $nextMeaningful = $tokens->getNextMeaningfulToken($index);
+
+                    // Return if the class is not a command
+                    if ('Command' !== substr($tokens[$nextMeaningful]->getContent(), -7)) {
+                        return;
+                    }
+                    break;
+
+                case $tokens[$index]->isGivenKind(T_FUNCTION):
+                    $nextMeaningful = $tokens->getNextMeaningfulToken($index);
+
+                    // Skip the method if it is not the configure() method
+                    if ('configure' !== $tokens[$nextMeaningful]->getContent()) {
+                        $nextMeaningful = $tokens->getNextMeaningfulToken($index);
+
+                        if ($tokens[$nextMeaningful]->isGivenKind('(')) {
+                            $index = $tokens->findBlockEnd(Tokens::BLOCK_TYPE_PARENTHESIS_BRACE, $nextMeaningful);
+                        }
+                    }
+                    break;
+
+                case $tokens[$index]->isGivenKind(T_OBJECT_OPERATOR):
+                    $nextMeaningful = $tokens->getNextMeaningfulToken($index);
+
+                    if (!\in_array($tokens[$nextMeaningful]->getContent(), ['addArgument', 'addOption'], true)) {
+                        continue 2;
+                    }
+
+                    $blockStart = $nextMeaningful + 1;
+                    $blockEnd = $tokens->findBlockEnd(Tokens::BLOCK_TYPE_PARENTHESIS_BRACE, $blockStart);
+
+                    for ($i = $blockStart; $i < $blockEnd; ++$i) {
+                        if ($tokens[$i]->isWhitespace()) {
+                            $tokens->clearAt($i);
+                        }
+                    }
+            }
+        }
+    }
+}
diff --git a/src/Sniffs/SetDefinitionCommandSniff.php b/src/Sniffs/SetDefinitionCommandSniff.php
new file mode 100644
index 0000000..6385256
--- /dev/null
+++ b/src/Sniffs/SetDefinitionCommandSniff.php
@@ -0,0 +1,41 @@
+<?php
+
+namespace Contao\EasyCodingStandard\Sniffs;
+
+use PHP_CodeSniffer\Files\File;
+use PHP_CodeSniffer\Sniffs\Sniff;
+
+final class SetDefinitionCommandSniff implements Sniff
+{
+    private $isConfigure = false;
+
+    public function register(): array
+    {
+        return [T_CLASS, T_FUNCTION, T_OBJECT_OPERATOR];
+    }
+
+    public function process(File $file, $index)
+    {
+        $tokens = $file->getTokens();
+
+        switch (true) {
+            case T_CLASS === $tokens[$index]['code']:
+                if ('Command' !== substr($tokens[$index + 2]['content'], -7)) {
+                    return \count($tokens) + 1;
+                }
+                break;
+
+            case T_FUNCTION === $tokens[$index]['code']:
+                $this->isConfigure = 'configure' === $tokens[$index + 2]['content'];
+                break;
+
+            case T_OBJECT_OPERATOR === $tokens[$index]['code']:
+                if ($this->isConfigure && 'setDefinition' === $tokens[$index + 1]['content']) {
+                    $file->addError('Do not use the setDefinition() method to configure commands. Use addArgument() and addOption() instead.', $index, self::class);
+                }
+                break;
+        }
+
+        return \count($tokens) + 1;
+    }
+}