diff --git a/src/c3nav/mapdata/management/commands/checkmap.py b/src/c3nav/mapdata/management/commands/checkmap.py
new file mode 100644
index 00000000..ed1d03c8
--- /dev/null
+++ b/src/c3nav/mapdata/management/commands/checkmap.py
@@ -0,0 +1,30 @@
+import os
+import tempfile
+
+from django.core.management import call_command
+from django.core.management.base import BaseCommand
+from django.db import connections
+
+
+class Command(BaseCommand):
+    help = 'Check if there are errors in the map package files'
+
+    def add_arguments(self, parser):
+        parser.add_argument('--no-prettify', dest='prettify', action='store_const', const=False, default=True,
+                            help='ignore formatting errors')
+
+    def handle(self, *args, **options):
+        print('Creating temporary database for checking…\n')
+
+        _, tmp = tempfile.mkstemp(suffix='.sqlite3', prefix='c3nav-checkmap-')
+        connections.databases['tmpdb'] = {
+            'ENGINE': 'django.db.backends.sqlite3',
+            'NAME': tmp,
+        }
+
+        try:
+            call_command('migrate', database='tmpdb')
+            call_command('loadmap', yes=True)
+            call_command('dumpmap', prettify=options['prettify'], check_only=True)
+        finally:
+            os.remove(tmp)
diff --git a/src/c3nav/mapdata/management/commands/dumpmap.py b/src/c3nav/mapdata/management/commands/dumpmap.py
index b08510ba..79f03351 100644
--- a/src/c3nav/mapdata/management/commands/dumpmap.py
+++ b/src/c3nav/mapdata/management/commands/dumpmap.py
@@ -1,17 +1,23 @@
-from django.core.management.base import BaseCommand
-from django.db import transaction
+from django.core.management.base import BaseCommand, CommandError
 
 from ...packageio import write_packages
 
 
 class Command(BaseCommand):
-    help = 'Dump the map database'
+    help = 'Dump the map database into the map package files'
 
     def add_arguments(self, parser):
         parser.add_argument('--no-prettify', dest='prettify', action='store_const', const=False, default=True,
                             help='dont\'t prettify existing files')
+        parser.add_argument('--check-only', action='store_const', const=True, default=False,
+                            help='check if there are files to update')
 
     def handle(self, *args, **options):
-        with transaction.atomic():
-            write_packages(prettify=options['prettify'])
-            print()
+        count = write_packages(prettify=options['prettify'], check_only=options['check_only'])
+        if options['check_only']:
+            if count == 0:
+                print('No errors found!')
+            else:
+                raise CommandError('Found errors in %s file(s)' % count)
+        else:
+            print('%s file(s) affected' % count)
diff --git a/src/c3nav/mapdata/management/commands/loadmap.py b/src/c3nav/mapdata/management/commands/loadmap.py
index c31af94f..e160b2ed 100644
--- a/src/c3nav/mapdata/management/commands/loadmap.py
+++ b/src/c3nav/mapdata/management/commands/loadmap.py
@@ -5,15 +5,15 @@ from ...packageio import read_packages
 
 
 class Command(BaseCommand):
-    help = 'Update the map database'
+    help = 'Load the map package files into the database'
 
     def add_arguments(self, parser):
-        parser.add_argument('-y', action='store_const', const=True, default=False,
+        parser.add_argument('--yes', '-y', action='store_const', const=True, default=False,
                             help='don\'t ask for confirmation')
 
     def handle(self, *args, **options):
         with transaction.atomic():
             read_packages()
             print()
-            if input('Confirm (y/N): ') != 'y':
+            if not options['yes'] and input('Confirm (y/N): ') != 'y':
                 raise CommandError('Aborted.')
diff --git a/src/c3nav/mapdata/packageio/write.py b/src/c3nav/mapdata/packageio/write.py
index a4b95735..d68e0a0a 100644
--- a/src/c3nav/mapdata/packageio/write.py
+++ b/src/c3nav/mapdata/packageio/write.py
@@ -1,63 +1,111 @@
+import difflib
 import json
 import os
+import sys
+from datetime import datetime
 
 from django.conf import settings
+from django.utils import timezone
 
 from ..models import Package
 from .utils import json_encode
 
 
-def write_packages(prettify=False):
-    print('Writing Map Packages…')
+def write_packages(prettify=False, check_only=False):
+    if not check_only:
+        sys.out.write('Writing Map Packages…')
+
+    count = 0
     for package in Package.objects.all():
-        print('\n'+package.name)
-        write_package(package, prettify)
+        if not check_only:
+            sys.out.write('\n'+package.name)
+        count += write_package(package, prettify, check_only)
+    return count
 
 
-def write_package(package, prettify=False):
-    pkg_path = os.path.join(settings.MAP_ROOT, package.directory)
-
-    with open(os.path.join(pkg_path, 'pkg.json'), 'w') as f:
-        f.write(json_encode(package.tofile()))
-
-    _write_folder(package, package.levels.all(), 'levels', prettify)
-    _write_folder(package, package.sources.all(), 'sources', prettify, check_sister_file=True)
+def write_package(package, prettify=False, check_only=False):
+    count = 0
+    count += _write_object(package, package.directory, 'pkg.json', prettify, check_only)
+    count += _write_folder(package.levels.all(), os.path.join(package.directory, 'levels'), prettify, check_only)
+    count += _write_folder(package.sources.all(), os.path.join(package.directory, 'sources'), prettify, check_only,
+                           check_sister_file=True)
+    return count
 
 
-def _write_folder(package, objects, path, prettify=False, check_sister_file=False):
+def _write_folder(objects, path, prettify=False, check_only=False, check_sister_file=False):
+    count = 0
     filenames = set()
-    full_path = os.path.join(settings.MAP_ROOT, package.directory, path)
+    full_path = os.path.join(settings.MAP_ROOT, path)
     if objects:
         if not os.path.isdir(full_path):
             os.mkdir(full_path)
         for obj in objects:
             filename = '%s.json' % obj.name
             filenames.add(filename)
+            count += _write_object(obj, path, filename, prettify, check_only)
 
+    if os.path.isdir(full_path):
+        for filename in os.listdir(full_path):
             full_filename = os.path.join(full_path, filename)
-            new_data = obj.tofile()
-            new_data_encoded = json_encode(new_data)
-            if os.path.isfile(full_filename):
-                with open(full_filename) as f:
-                    old_data_encoded = f.read()
-                old_data = json.loads(old_data_encoded, parse_int=float)
-                if old_data != json.loads(new_data_encoded, parse_int=float):
-                    print('- Updated: '+os.path.join(path, filename))
-                elif old_data_encoded != new_data_encoded:
-                    if not prettify:
-                        continue
-                    print('- Beautified: '+os.path.join(path, filename))
-                else:
-                    continue
-            else:
-                print('- Created: '+os.path.join(path, filename))
-            with open(full_filename, 'w') as f:
-                f.write(new_data_encoded)
+            if filename in filenames or not filename.endswith('.json') or not os.path.isfile(full_filename):
+                continue
 
-    if os.path.isdir(path):
-        for filename in os.listdir(path):
-            full_filename = os.path.join(path, filename)
-            if filename not in filenames and filename.endswith('.json') and os.path.isfile(full_filename):
+            count += 1
+            if check_only:
+                sys.stdout.writelines(difflib.unified_diff(
+                    list(open(full_filename)),
+                    [],
+                    fromfiledate=timezone.make_aware(
+                        datetime.fromtimestamp(os.path.getmtime(full_filename))
+                    ).isoformat(),
+                    tofiledate=timezone.make_aware(datetime.fromtimestamp(0)).isoformat(),
+                    fromfile=os.path.join(path, filename),
+                    tofile=os.path.join(path, filename)
+                ))
+            else:
                 os.remove(full_filename)
                 if check_sister_file and os.path.isfile(full_filename[:-5]):
                     os.remove(full_filename[:-5])
+    return count
+
+
+def _write_object(obj, path, filename, prettify=False, check_only=False):
+    full_path = os.path.join(settings.MAP_ROOT, path)
+    full_filename = os.path.join(full_path, filename)
+    new_data = obj.tofile()
+    new_data_encoded = json_encode(new_data)
+    old_data = None
+    old_data_encoded = None
+    if os.path.isfile(full_filename):
+        with open(full_filename) as f:
+            old_data_encoded = f.read()
+        old_data = json.loads(old_data_encoded, parse_int=float)
+        if old_data != json.loads(new_data_encoded, parse_int=float):
+            if not check_only:
+                sys.stdout.write('- Updated: '+os.path.join(path, filename))
+        elif old_data_encoded != new_data_encoded:
+            if not prettify:
+                return 0
+            if not check_only:
+                sys.stdout.write('- Beautified: '+os.path.join(path, filename))
+        else:
+            return 0
+    else:
+        if not check_only:
+            sys.stdout.write('- Created: '+os.path.join(path, filename))
+
+    if check_only:
+        sys.stdout.writelines(difflib.unified_diff(
+            [] if old_data is None else [(line+'\n') for line in old_data_encoded.split('\n')],
+            [(line+'\n') for line in new_data_encoded.split('\n')],
+            fromfiledate=timezone.make_aware(
+                datetime.fromtimestamp(0 if old_data is None else os.path.getmtime(full_filename))
+            ).isoformat(),
+            tofiledate=timezone.now().isoformat(),
+            fromfile=os.path.join(path, filename),
+            tofile=os.path.join(path, filename)
+        ))
+    else:
+        with open(full_filename, 'w') as f:
+            f.write(new_data_encoded)
+    return 1