diff --git a/selfdrive/ui/qt/widgets/input.cc b/selfdrive/ui/qt/widgets/input.cc
index c45aa0ad..cc0dada7 100644
--- a/selfdrive/ui/qt/widgets/input.cc
+++ b/selfdrive/ui/qt/widgets/input.cc
@@ -3,7 +3,7 @@
 #include "input.hpp"
 #include "qt_window.hpp"
 
-InputDialog::InputDialog(QString prompt_text, QWidget *parent):QDialog(parent) {
+InputDialog::InputDialog(const QString &prompt_text, QWidget *parent) : QDialog(parent) {
   layout = new QVBoxLayout();
   layout->setContentsMargins(50, 50, 50, 50);
   layout->setSpacing(20);
@@ -43,7 +43,7 @@ InputDialog::InputDialog(QString prompt_text, QWidget *parent):QDialog(parent) {
   layout->addWidget(line, 1, Qt::AlignTop);
 
   k = new Keyboard(this);
-  QObject::connect(k, SIGNAL(emitButton(QString)), this, SLOT(handleInput(QString)));
+  QObject::connect(k, SIGNAL(emitButton(const QString&)), this, SLOT(handleInput(const QString&)));
   layout->addWidget(k, 2, Qt::AlignBottom);
 
   setStyleSheet(R"(
@@ -56,7 +56,7 @@ InputDialog::InputDialog(QString prompt_text, QWidget *parent):QDialog(parent) {
   setLayout(layout);
 }
 
-QString InputDialog::getText(const QString prompt, int minLength) {
+QString InputDialog::getText(const QString &prompt, int minLength) {
   InputDialog d = InputDialog(prompt);
   d.setMinLength(minLength);
   const int ret = d.exec();
@@ -76,7 +76,7 @@ void InputDialog::show(){
   setMainWindow(this);
 }
 
-void InputDialog::handleInput(QString s) {
+void InputDialog::handleInput(const QString &s) {
   if (!QString::compare(s,"⌫")) {
     line->backspace();
   }
@@ -100,7 +100,7 @@ void InputDialog::handleInput(QString s) {
   line->insert(s.left(1));
 }
 
-void InputDialog::setMessage(QString message, bool clearInputField){
+void InputDialog::setMessage(const QString &message, bool clearInputField){
   label->setText(message);
   if (clearInputField){
     line->setText("");
@@ -112,7 +112,7 @@ void InputDialog::setMinLength(int length){
 }
 
 
-ConfirmationDialog::ConfirmationDialog(QString prompt_text, QString confirm_text, QString cancel_text,
+ConfirmationDialog::ConfirmationDialog(const QString &prompt_text, const QString &confirm_text, const QString &cancel_text,
                                        QWidget *parent):QDialog(parent) {
   setWindowFlags(Qt::Popup);
   layout = new QVBoxLayout();
@@ -161,12 +161,12 @@ ConfirmationDialog::ConfirmationDialog(QString prompt_text, QString confirm_text
   setLayout(layout);
 }
 
-bool ConfirmationDialog::alert(const QString prompt_text) {
+bool ConfirmationDialog::alert(const QString &prompt_text) {
   ConfirmationDialog d = ConfirmationDialog(prompt_text, "Ok", "");
   return d.exec();
 }
 
-bool ConfirmationDialog::confirm(const QString prompt_text) {
+bool ConfirmationDialog::confirm(const QString &prompt_text) {
   ConfirmationDialog d = ConfirmationDialog(prompt_text);
   return d.exec();
 }
diff --git a/selfdrive/ui/qt/widgets/input.hpp b/selfdrive/ui/qt/widgets/input.hpp
index a5d0dd90..f52ad441 100644
--- a/selfdrive/ui/qt/widgets/input.hpp
+++ b/selfdrive/ui/qt/widgets/input.hpp
@@ -13,10 +13,10 @@ class InputDialog : public QDialog {
   Q_OBJECT
 
 public:
-  explicit InputDialog(QString prompt_text, QWidget* parent = 0);
-  static QString getText(QString prompt, int minLength = -1);
+  explicit InputDialog(const QString &prompt_text, QWidget* parent = 0);
+  static QString getText(const QString &prompt, int minLength = -1);
   QString text();
-  void setMessage(QString message, bool clearInputField=true);
+  void setMessage(const QString &message, bool clearInputField = true);
   void setMinLength(int length);
   void show();
 
@@ -31,21 +31,21 @@ public slots:
   int exec() override;
 
 private slots:
-  void handleInput(QString s);
+  void handleInput(const QString &s);
 
 signals:
   void cancel();
-  void emitText(QString text);
+  void emitText(const QString &text);
 };
 
 class ConfirmationDialog : public QDialog {
   Q_OBJECT
 
 public:
-  explicit ConfirmationDialog(QString prompt_text, QString confirm_text = "Ok",
-                              QString cancel_text = "Cancel", QWidget* parent = 0);
-  static bool alert(QString prompt_text);
-  static bool confirm(QString prompt_text);
+  explicit ConfirmationDialog(const QString &prompt_text, const QString &confirm_text = "Ok",
+                              const QString &cancel_text = "Cancel", QWidget* parent = 0);
+  static bool alert(const QString &prompt_text);
+  static bool confirm(const QString &prompt_text);
 
 private:
   QLabel *prompt;
diff --git a/selfdrive/ui/qt/widgets/keyboard.cc b/selfdrive/ui/qt/widgets/keyboard.cc
index 4dbcc281..0eda100e 100644
--- a/selfdrive/ui/qt/widgets/keyboard.cc
+++ b/selfdrive/ui/qt/widgets/keyboard.cc
@@ -10,7 +10,7 @@
 const int DEFAULT_STRETCH = 1;
 const int SPACEBAR_STRETCH = 3;
 
-KeyboardLayout::KeyboardLayout(QWidget *parent, std::vector<QVector<QString>> layout) : QWidget(parent) {
+KeyboardLayout::KeyboardLayout(QWidget* parent, const std::vector<QVector<QString>>& layout) : QWidget(parent) {
   QVBoxLayout* vlayout = new QVBoxLayout;
   vlayout->setMargin(0);
   vlayout->setSpacing(35);
diff --git a/selfdrive/ui/qt/widgets/keyboard.hpp b/selfdrive/ui/qt/widgets/keyboard.hpp
index 2204973f..5ff50382 100644
--- a/selfdrive/ui/qt/widgets/keyboard.hpp
+++ b/selfdrive/ui/qt/widgets/keyboard.hpp
@@ -12,7 +12,7 @@ class KeyboardLayout : public QWidget {
   Q_OBJECT
 
 public:
-  explicit KeyboardLayout(QWidget *parent, std::vector<QVector<QString>> layout);
+ explicit KeyboardLayout(QWidget* parent, const std::vector<QVector<QString>>& layout);
 };
 
 class Keyboard : public QFrame {
@@ -28,5 +28,5 @@ private slots:
   void handleButton(QAbstractButton* m_button);
 
 signals:
-  void emitButton(QString s);
+  void emitButton(const QString &s);
 };