diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 00000000..28f5570e
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,20 @@
+# https://editorconfig.org
+
+# Tip: to find files violating the rules set out here, run `docker run --rm --volume=$PWD:/check mstruebing/editorconfig-checker`
+
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_size = 4
+indent_style = space
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.yaml]
+indent_size = 2
+
+
+[*.yml]
+indent_size = 2
diff --git a/app/.editorconfig b/app/.editorconfig
index 5ce64346..ae6caa62 100644
--- a/app/.editorconfig
+++ b/app/.editorconfig
@@ -1,19 +1,12 @@
 # https://editorconfig.org
 
+# note: the files in ./composer actually use 4 spaces instead of tabs
+
 root = true
 
 [*]
 charset = utf-8
 end_of_line = lf
-indent_size = 4
 indent_style = tab
 insert_final_newline = true
 trim_trailing_whitespace = true
-
-[*.feature]
-indent_size = 2
-indent_style = space
-
-[*.yml]
-indent_size = 2
-indent_style = space
diff --git a/php/psalm.xml b/php/psalm.xml
index 576d82d2..ec4461c5 100644
--- a/php/psalm.xml
+++ b/php/psalm.xml
@@ -1,29 +1,29 @@
 <?xml version="1.0"?>
 <psalm
-	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-	xmlns="https://getpsalm.org/schema/config"
-	xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
-	errorBaseline="psalm-baseline.xml"
-	findUnusedBaselineEntry="true"
-	findUnusedCode="false"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns="https://getpsalm.org/schema/config"
+    xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
+    errorBaseline="psalm-baseline.xml"
+    findUnusedBaselineEntry="true"
+    findUnusedCode="false"
 >
-	<projectFiles>
-		<directory name="templates"/>
-		<directory name="src"/>
-		<file name="public/index.php"/>
-		<ignoreFiles>
-			<directory name="vendor" />
-		</ignoreFiles>
-	</projectFiles>
-	<extraFiles>
-		<directory name="vendor" />
-	</extraFiles>
-	<issueHandlers>
-  		<ClassMustBeFinal errorLevel="suppress" />
+    <projectFiles>
+        <directory name="templates"/>
+        <directory name="src"/>
+        <file name="public/index.php"/>
+        <ignoreFiles>
+            <directory name="vendor" />
+        </ignoreFiles>
+    </projectFiles>
+    <extraFiles>
+        <directory name="vendor" />
+    </extraFiles>
+    <issueHandlers>
+        <ClassMustBeFinal errorLevel="suppress" />
         <MissingConstructor>
             <errorLevel type="suppress">
                 <file name="src/Data/ConfigurationManager.php" />  <!-- We're using property hooks with virtual properties in that file, which Psalm wrongly complains about. See <https://github.com/vimeo/psalm/issues/11435>.  -->
             </errorLevel>
         </MissingConstructor>
-	</issueHandlers>
+    </issueHandlers>
 </psalm>