diff --git a/web/flaskr/__init__.py b/web/flaskr/__init__.py
index 6ff8749f..6ef16f1a 100755
--- a/web/flaskr/__init__.py
+++ b/web/flaskr/__init__.py
@@ -25,19 +25,7 @@
 LANGUAGES = ["en", "fr"]
 
 
-def setup_babel(app):
-    babel = Babel(app)
-
-    @babel.localeselector
-    def get_locale():
-        if request.args.get("lang"):
-            session["lang"] = request.args["lang"]
-        return session.get("lang", "fr")
-
-
-def create_app(test_config=None, gunicorn_logging=False):
-    # create and configure the app
-    app = Flask(__name__, instance_relative_config=True)
+def setup_cache(app):
     cache.init_app(
         app,
         config={
@@ -45,6 +33,9 @@ def create_app(test_config=None, gunicorn_logging=False):
             "CACHE_DIR": "/tmp/flask-caching",
         },
     )
+
+
+def setup_logging(app, test_config=None, gunicorn_logging=False):
     if gunicorn_logging:
         gunicorn_logger = logging.getLogger("gunicorn.error")
         app.logger.handlers = gunicorn_logger.handlers
@@ -53,6 +44,34 @@ def create_app(test_config=None, gunicorn_logging=False):
     if test_config:
         app.config.from_mapping(test_config)
 
+
+def setup_i18n(app):
+    babel = Babel(app)
+
+    @babel.localeselector
+    def get_locale():
+        if request.args.get("lang"):
+            session["lang"] = request.args["lang"]
+        return session.get("lang", "fr")
+
+
+def setup_csrf(app):
+    csrf = CSRFProtect()
+    csrf.init_app(app)
+
+
+def setup_database(app):
+    with app.app_context():
+        import flaskr.routes
+
+        app.register_blueprint(flaskr.routes.bp)
+        from .models import db
+
+        db.init_app(app)
+        Migrate(app, db, compare_type=True)
+
+
+def setup_jinja(app):
     @app.context_processor
     def global_processor():
         return {
@@ -64,22 +83,37 @@ def global_processor():
             **app.config["WORDINGS"],
         }
 
-    # translations
-    setup_babel(app)
 
-    # Protect App Form with CSRF
-    csrf = CSRFProtect()
-    csrf.init_app(app)
+def setup_error_pages(app):
+    from flask import render_template
 
-    # init database
-    with app.app_context():
-        import flaskr.routes
+    @app.errorhandler(400)
+    def bad_request(error):
+        return render_template("errors/400.html", error=error), 400
 
-        app.register_blueprint(flaskr.routes.bp)
-        from .models import db
+    @app.errorhandler(403)
+    def not_authorized(error):
+        return render_template("errors/403.html", error=error), 403
 
-        db.init_app(app)
-        Migrate(app, db, compare_type=True)
+    @app.errorhandler(404)
+    def not_found(error):
+        return render_template("errors/404.html", error=error), 404
+
+    @app.errorhandler(500)
+    def internal_error(error):
+        return render_template("errors/500.html", error=error), 500
+
+
+def create_app(test_config=None, gunicorn_logging=False):
+    # create and configure the app
+    app = Flask(__name__, instance_relative_config=True)
+    setup_cache(app)
+    setup_logging(app, test_config, gunicorn_logging)
+    setup_i18n(app)
+    setup_csrf(app)
+    setup_database(app)
+    setup_jinja(app)
+    setup_error_pages(app)
 
     # ensure the instance folder exists
     os.makedirs(app.instance_path, exist_ok=True)
diff --git a/web/flaskr/routes.py b/web/flaskr/routes.py
index 50357b09..560e68ea 100755
--- a/web/flaskr/routes.py
+++ b/web/flaskr/routes.py
@@ -1544,33 +1544,3 @@ def delete_video_meeting():
 @auth.oidc_logout
 def logout():
     return redirect(url_for("routes.index"))
-
-
-@current_app.errorhandler(403)
-def page_not_authorized(e):
-    return (
-        render_template(
-            "errors/403.html",
-        ),
-        403,
-    )
-
-
-@current_app.errorhandler(404)
-def page_not_found(e):
-    return (
-        render_template(
-            "errors/404.html",
-        ),
-        404,
-    )
-
-
-@current_app.errorhandler(500)
-def page_error(e):
-    return (
-        render_template(
-            "errors/500.html",
-        ),
-        500,
-    )
diff --git a/web/flaskr/templates/errors/400.html b/web/flaskr/templates/errors/400.html
new file mode 100644
index 00000000..d42677d6
--- /dev/null
+++ b/web/flaskr/templates/errors/400.html
@@ -0,0 +1,18 @@
+{% extends 'layout.html' %}
+
+{% block main %}
+<div class="fr-container">
+    <div class="fr-grid-row fr-grid-row--center">
+      <div class="fr-col-md-6">
+        <h1 class="fr-h2">{% trans %}Erreur 400{% endtrans %}</h1>
+        <p>
+        {% if error %}
+            {{ error }}
+        {% else %}
+            {% trans %}La requête que vous avez effectué est invalide. Vous pouvez <a href="/">retourner à l’accueil</a>.{% endtrans %}
+        {% endif %}
+        </p>
+      </div>
+    </div>
+</div>
+{% endblock %}
diff --git a/web/tests/test_default.py b/web/tests/test_default.py
index b42d506a..04c42ce0 100644
--- a/web/tests/test_default.py
+++ b/web/tests/test_default.py
@@ -1,6 +1,40 @@
+from flask import abort
 from flask import url_for
 
 
+def test_custom_400(client_app):
+    @client_app.app.route("/custom_400")
+    def custom_400():
+        abort(400, "custom error message")
+
+    response = client_app.get("/custom_400", status=400)
+    response.mustcontain("Erreur 400")
+    response.mustcontain("custom error message")
+
+
+def test_custom_404(client_app):
+    response = client_app.get("/invalid-url", status=404)
+    response.mustcontain("Erreur 404")
+
+
+def test_custom_403(client_app):
+    @client_app.app.route("/custom_403")
+    def custom_403():
+        abort(403)
+
+    response = client_app.get("/custom_403", status=403)
+    response.mustcontain("Erreur 403")
+
+
+def test_custom_500(client_app):
+    @client_app.app.route("/custom_500")
+    def custom_500():
+        abort(500)
+
+    response = client_app.get("/custom_500", status=500)
+    response.mustcontain("Erreur 500")
+
+
 def test_root__anonymous_user(client_app):
     response = client_app.get("/", status=302)