diff --git a/src/client/outputconfiguration.h b/src/client/outputconfiguration.h
--- a/src/client/outputconfiguration.h
+++ b/src/client/outputconfiguration.h
@@ -228,6 +228,18 @@
      */
     void setColorCurves(OutputDevice *outputdevice, QVector<quint16> red, QVector<quint16> green, QVector<quint16> blue);
 
+
+    /**
+     * Logical size of this output.
+     * The changes done in this call will be recorded in the
+     * OutputDevice and only applied after apply() has been called.
+     *
+     * @param size the logical size for this output device.
+     * @param outputdevice the OutputDevice this change applies to.
+     * @since 5.66
+     */
+    void setLogicalSize(OutputDevice *outputdevice, const QSizeF &size);
+
     /**
      * Ask the compositor to apply the changes.
      * This results in the compositor looking at all outputdevices and if they have
diff --git a/src/client/outputconfiguration.cpp b/src/client/outputconfiguration.cpp
--- a/src/client/outputconfiguration.cpp
+++ b/src/client/outputconfiguration.cpp
@@ -201,6 +201,14 @@
     wl_array_release(&wlBlue);
 }
 
+void OutputConfiguration::setLogicalSize(OutputDevice *outputdevice, const QSizeF &size)
+{
+    org_kde_kwin_outputdevice *od = outputdevice->output();
+    org_kde_kwin_outputconfiguration_logical_size(d->outputconfiguration, od,
+                                                  wl_fixed_from_double(size.width()),
+                                                  wl_fixed_from_double(size.height()));
+}
+
 void OutputConfiguration::apply()
 {
     org_kde_kwin_outputconfiguration_apply(d->outputconfiguration);
diff --git a/src/client/outputdevice.h b/src/client/outputdevice.h
--- a/src/client/outputdevice.h
+++ b/src/client/outputdevice.h
@@ -95,6 +95,7 @@
         Disabled = 0,
         Enabled = 1
     };
+
     struct Mode {
         enum class Flag {
             None = 0,
@@ -179,6 +180,12 @@
      * Size in the current mode.
      **/
     QSize pixelSize() const;
+    /**
+     * Size in compositor space.
+     **/
+    QSizeF logicalSize() const;
+
+    // TODO KF6: in geometry() replace pixel size with the logical size
     /**
      * The geometry of this OutputDevice in pixels.
      * Convenient for QRect(globalPosition(), pixelSize()).
diff --git a/src/client/outputdevice.cpp b/src/client/outputdevice.cpp
--- a/src/client/outputdevice.cpp
+++ b/src/client/outputdevice.cpp
@@ -48,6 +48,7 @@
     EventQueue *queue = nullptr;
     QSize physicalSize;
     QPoint globalPosition;
+    QSizeF logicalSize = QSizeF();
     QString manufacturer;
     QString model;
     qreal scale = 1.0;
@@ -84,9 +85,12 @@
 
     static void serialNumberCallback(void *data, org_kde_kwin_outputdevice *output, const char *serialNumber);
     static void eisaIdCallback(void *data, org_kde_kwin_outputdevice *output, const char *eisa);
+    static void logicalSizeCallback(void *data, org_kde_kwin_outputdevice *output,
+                                    wl_fixed_t width, wl_fixed_t height);
 
     void setPhysicalSize(const QSize &size);
     void setGlobalPosition(const QPoint &pos);
+    void setLogicalSize(const QSizeF &size);
     void setManufacturer(const QString &manufacturer);
     void setModel(const QString &model);
     void setScale(qreal scale);
@@ -151,7 +155,8 @@
     scaleFCallback,
     colorcurvesCallback,
     serialNumberCallback,
-    eisaIdCallback
+    eisaIdCallback,
+    logicalSizeCallback
 };
 
 void OutputDevice::Private::geometryCallback(void *data, org_kde_kwin_outputdevice *output,
@@ -313,6 +318,14 @@
     }
 }
 
+void OutputDevice::Private::logicalSizeCallback(void *data, org_kde_kwin_outputdevice *output,
+                                                wl_fixed_t width, wl_fixed_t height)
+{
+    auto o = reinterpret_cast<OutputDevice::Private*>(data);
+    Q_ASSERT(o->output == output);
+    o->setLogicalSize(QSizeF(wl_fixed_to_double(width), wl_fixed_to_double(height)));
+}
+
 void OutputDevice::Private::uuidCallback(void* data, org_kde_kwin_outputdevice* output, const char *uuid)
 {
     Q_UNUSED(output);
@@ -417,6 +430,11 @@
     scale = s;
 }
 
+void OutputDevice::Private::setLogicalSize(const QSizeF &size)
+{
+    logicalSize = size;
+}
+
 QRect OutputDevice::geometry() const
 {
     if (d->currentMode == d->modes.end()) {
@@ -545,6 +563,11 @@
     return d->colorCurves;
 }
 
+QSizeF OutputDevice::logicalSize() const
+{
+    return d->logicalSize;
+}
+
 void OutputDevice::destroy()
 {
     d->output.destroy();
diff --git a/src/client/protocols/output-management.xml b/src/client/protocols/output-management.xml
--- a/src/client/protocols/output-management.xml
+++ b/src/client/protocols/output-management.xml
@@ -28,7 +28,7 @@
         THIS SOFTWARE.
         ]]></copyright>
 
-<interface name="org_kde_kwin_outputmanagement" version="2">
+<interface name="org_kde_kwin_outputmanagement" version="3">
     <description summary="configuration of server outputs through clients">
     This interface enables clients to set properties of output devices for screen
     configuration purposes via the server. To this end output devices are referenced
@@ -80,7 +80,7 @@
 
 </interface>
 
-<interface name="org_kde_kwin_outputconfiguration" version="2">
+<interface name="org_kde_kwin_outputconfiguration" version="3">
     <description summary="configure single output devices">
         outputconfiguration is a client-specific resource that can be used to ask
         the server to apply changes to available output devices.
@@ -190,6 +190,26 @@
         <description summary="release the outputconfiguration object"/>
     </request>
 
+    <request name="logical_size" since="3">
+        <description summary="set logical size in compositor space">
+            This requests sets the logcial size the output is depicting explicitly. When using this
+            request changes to mode or scale will not influence the logical size.
+
+            Arguments width and height must be positive, or both equal 0 or both equal -1.
+
+            If both arguments are 0 the compositor should temporarily ignore the output as if it has
+            been switched off or disconnected.
+
+            If both arguments are equal -1 the logical size is unset and the compositor is supposed
+            to calculate the output representation in the compositor space again from the output's
+            mode and scale.
+        </description>
+        <arg name="outputdevice" type="object" interface="org_kde_kwin_outputdevice"
+             summary="outputdevice curves apply to"/>
+        <arg name="width" type="fixed" summary="new logical width"/>
+        <arg name="height" type="fixed" summary="new logical height"/>
+    </request>
+
 </interface>
 
 </protocol>
diff --git a/src/client/protocols/outputdevice.xml b/src/client/protocols/outputdevice.xml
--- a/src/client/protocols/outputdevice.xml
+++ b/src/client/protocols/outputdevice.xml
@@ -29,7 +29,7 @@
         ]]></copyright>
 
 
-<interface name="org_kde_kwin_outputdevice" version="2">
+<interface name="org_kde_kwin_outputdevice" version="3">
     <description summary="output configuration representation">
         An outputdevice describes a display device available to the compositor.
         outputdevice is similar to wl_output, but focuses on output
@@ -280,14 +280,25 @@
         <arg name="serialNumber" type="string"
                 summary="textual representation of serial number"/>
     </event>
+
     <event name="eisa_id" since="2">
         <description summary="EISA ID">
             EISA ID of the monitor, sent on startup before the first done event.
         </description>
         <arg name="eisaId" type="string"
              summary="textual representation of EISA identifier"/>
     </event>
 
+    <event name="logical_size" since="3">
+        <description summary="EISA ID">
+            Returns the logical size in compositor space. This event is always sent after
+            the logical size is changed and can be triggered by explicit logical size changes
+            in the configruation interface or implicitly through a scale or mode change.
+        </description>
+        <arg name="width" type="fixed" summary="logical width"/>
+        <arg name="height" type="fixed" summary="logical height"/>
+    </event>
+
 </interface>
 
 
diff --git a/src/client/registry.cpp b/src/client/registry.cpp
--- a/src/client/registry.cpp
+++ b/src/client/registry.cpp
@@ -213,14 +213,14 @@
         &Registry::fakeInputRemoved
     }},
     {Registry::Interface::OutputManagement, {
-        2,
+        3,
         QByteArrayLiteral("org_kde_kwin_outputmanagement"),
         &org_kde_kwin_outputmanagement_interface,
         &Registry::outputManagementAnnounced,
         &Registry::outputManagementRemoved
     }},
     {Registry::Interface::OutputDevice, {
-        2,
+        3,
         QByteArrayLiteral("org_kde_kwin_outputdevice"),
         &org_kde_kwin_outputdevice_interface,
         &Registry::outputDeviceAnnounced,
diff --git a/src/server/outputchangeset.h b/src/server/outputchangeset.h
--- a/src/server/outputchangeset.h
+++ b/src/server/outputchangeset.h
@@ -73,6 +73,11 @@
      * @returns @c true if the colorCurves() property of the outputdevice has changed.
      */
     bool colorCurvesChanged() const;
+    /** Whether the logicalSize() property of the outputdevice changed.
+     * @returns @c true if the logicalSize() property of the outputdevice has changed.
+     * @since 5.66
+     */
+    bool logicalSizeChanged() const;
 
     /** The new value for enabled. */
     OutputDeviceInterface::Enablement enabled() const;
@@ -97,6 +102,10 @@
      * @since 5.XX
      */
     OutputDeviceInterface::ColorCurves colorCurves() const;
+    /** The new value for logicalSize.
+     * @since 5.66
+     */
+    QSizeF logicalSize() const;
 
 private:
     friend class OutputConfigurationInterface;
diff --git a/src/server/outputchangeset.cpp b/src/server/outputchangeset.cpp
--- a/src/server/outputchangeset.cpp
+++ b/src/server/outputchangeset.cpp
@@ -35,6 +35,7 @@
     , position(o->globalPosition())
     , scale(o->scaleF())
     , colorCurves(o->colorCurves())
+    , logicalSize(o->logicalSize())
 {
 }
 
@@ -130,5 +131,17 @@
     return d->colorCurves;
 }
 
+bool OutputChangeSet::logicalSizeChanged() const
+{
+    Q_D();
+    return d->logicalSize != d->o->logicalSize();
+}
+
+QSizeF OutputChangeSet::logicalSize() const
+{
+    Q_D();
+    return d->logicalSize;
+}
+
 }
 }
diff --git a/src/server/outputchangeset_p.h b/src/server/outputchangeset_p.h
--- a/src/server/outputchangeset_p.h
+++ b/src/server/outputchangeset_p.h
@@ -42,6 +42,7 @@
             QPoint position;
             qreal scale;
             OutputDeviceInterface::ColorCurves colorCurves;
+            QSizeF logicalSize;
         };
     }
 }
diff --git a/src/server/outputconfiguration_interface.cpp b/src/server/outputconfiguration_interface.cpp
--- a/src/server/outputconfiguration_interface.cpp
+++ b/src/server/outputconfiguration_interface.cpp
@@ -55,7 +55,7 @@
     OutputManagementInterface *outputManagement;
     QHash<OutputDeviceInterface*, OutputChangeSet*> changes;
 
-    static const quint32 s_version = 2;
+    static const quint32 s_version = 3;
 
 private:
     static void enableCallback(wl_client *client, wl_resource *resource,
@@ -74,6 +74,9 @@
     static void colorcurvesCallback(wl_client *client, wl_resource *resource,
                                     wl_resource * outputdevice,
                                     wl_array *red, wl_array *green, wl_array *blue);
+    static void logicalSizeCallback(wl_client *client, wl_resource *resource,
+                                    wl_resource *outputdevice,
+                                    wl_fixed_t width, wl_fixed_t height);
 
     OutputConfigurationInterface *q_func() {
         return reinterpret_cast<OutputConfigurationInterface *>(q);
@@ -91,7 +94,8 @@
     applyCallback,
     scaleFCallback,
     colorcurvesCallback,
-    resourceDestroyedCallback
+    resourceDestroyedCallback,
+    logicalSizeCallback
 };
 
 OutputConfigurationInterface::OutputConfigurationInterface(OutputManagementInterface* parent, wl_resource* parentResource): Resource(new Private(this, parent, parentResource))
@@ -253,6 +257,19 @@
     s->pendingChanges(o)->d_func()->colorCurves = cc;
 }
 
+void OutputConfigurationInterface::Private::logicalSizeCallback(wl_client *client,
+                                                                wl_resource *resource,
+                                                                wl_resource * outputdevice,
+                                                                wl_fixed_t width, wl_fixed_t height)
+{
+    Q_UNUSED(client);
+    const QSizeF size(wl_fixed_to_double(width), wl_fixed_to_double(height));
+    OutputDeviceInterface *o = OutputDeviceInterface::get(outputdevice);
+    auto s = cast<Private>(resource);
+    Q_ASSERT(s);
+    s->pendingChanges(o)->d_func()->logicalSize = size;
+}
+
 void OutputConfigurationInterface::Private::emitConfigurationChangeRequested() const
 {
     auto configinterface = reinterpret_cast<OutputConfigurationInterface *>(q);
diff --git a/src/server/outputdevice_interface.h b/src/server/outputdevice_interface.h
--- a/src/server/outputdevice_interface.h
+++ b/src/server/outputdevice_interface.h
@@ -83,6 +83,7 @@
         Disabled = 0,
         Enabled = 1
     };
+
     enum class ModeFlag {
         Current = 1,
         Preferred = 2
@@ -122,12 +123,35 @@
     QList<Mode> modes() const;
     int currentModeId() const;
 
+    /**
+     * Current explicitly set size in compositor space. An invalid size is returned in case no size
+     * was explicitly set. In this case the output siez in compositor space should be computed
+     * from pixelSize() and scaleF().
+     *
+     * @return explicitly set logical size
+     *
+     * @see globalSize
+     *
+     * @since 5.66
+     */
+    QSizeF logicalSize() const;
+
     QByteArray edid() const;
     OutputDeviceInterface::Enablement enabled() const;
     QByteArray uuid() const;
 
     void setPhysicalSize(const QSize &size);
     void setGlobalPosition(const QPoint &pos);
+
+    /**
+     * Explicitly sets the logical size.
+     *
+     * @param size the explicitly set logical size
+     * @see logicalSize
+     *
+     * @since 5.66
+     */
+    void setLogicalSize(const QSizeF &size);
     void setManufacturer(const QString &manufacturer);
     void setModel(const QString &model);
     void setSerialNumber(const QString &serialNumber);
@@ -162,6 +186,7 @@
 Q_SIGNALS:
     void physicalSizeChanged(const QSize&);
     void globalPositionChanged(const QPoint&);
+    void logicalSizeChanged();
     void manufacturerChanged(const QString&);
     void modelChanged(const QString&);
     void serialNumberChanged(const QString&);
diff --git a/src/server/outputdevice_interface.cpp b/src/server/outputdevice_interface.cpp
--- a/src/server/outputdevice_interface.cpp
+++ b/src/server/outputdevice_interface.cpp
@@ -50,6 +50,7 @@
     void updateColorCurves();
     void updateEisaId();
     void updateSerialNumber();
+    void updateLogicalSize();
 
     void sendGeometry(wl_resource *resource);
     void sendMode(wl_resource *resource, const Mode &mode);
@@ -61,9 +62,11 @@
     void sendColorCurves(const ResourceData &data);
     void sendEisaId(const ResourceData &data);
     void sendSerialNumber(const ResourceData &data);
+    void sendLogicalSize(const ResourceData &data);
 
     QSize physicalSize;
     QPoint globalPosition;
+    QSizeF logicalSize;
     QString manufacturer = QStringLiteral("org.kde.kwin");
     QString model = QStringLiteral("none");
     qreal scale = 1.0;
@@ -94,7 +97,7 @@
     static QVector<Private*> s_privates;
 };
 
-const quint32 OutputDeviceInterface::Private::s_version = 2;
+const quint32 OutputDeviceInterface::Private::s_version = 3;
 
 QVector<OutputDeviceInterface::Private*> OutputDeviceInterface::Private::s_privates;
 
@@ -152,6 +155,8 @@
     connect(this, &OutputDeviceInterface::scaleFChanged,          this, [d] { d->updateScale(); });
     connect(this, &OutputDeviceInterface::scaleChanged,          this, [d] { d->updateScale(); });
     connect(this, &OutputDeviceInterface::colorCurvesChanged,    this, [d] { d->updateColorCurves(); });
+    connect(this, &OutputDeviceInterface::logicalSizeChanged,
+            this, [d] { d->updateLogicalSize(); });
 }
 
 OutputDeviceInterface::~OutputDeviceInterface() = default;
@@ -341,6 +346,7 @@
 
     sendGeometry(resource);
     sendScale(r);
+    sendLogicalSize(r);
     sendColorCurves(r);
     sendEisaId(r);
     sendSerialNumber(r);
@@ -420,6 +426,17 @@
     }
 }
 
+void OutputDeviceInterface::Private::sendLogicalSize(const ResourceData &data)
+{
+    if (wl_resource_get_version(data.resource) <
+            ORG_KDE_KWIN_OUTPUTDEVICE_LOGICAL_SIZE_SINCE_VERSION) {
+        return;
+    }
+    org_kde_kwin_outputdevice_send_logical_size(data.resource,
+                                                wl_fixed_from_double(logicalSize.width()),
+                                                wl_fixed_from_double(logicalSize.height()));
+}
+
 void OutputDeviceInterface::Private::sendColorCurves(const ResourceData &data)
 {
     if (data.version < ORG_KDE_KWIN_OUTPUTDEVICE_COLORCURVES_SINCE_VERSION) {
@@ -483,6 +500,14 @@
     }
 }
 
+void OutputDeviceInterface::Private::updateLogicalSize()
+{
+    for (auto it = resources.constBegin(); it != resources.constEnd(); ++it) {
+        sendLogicalSize(*it);
+        sendDone(*it);
+    }
+}
+
 void OutputDeviceInterface::Private::updateColorCurves()
 {
     for (auto it = resources.constBegin(); it != resources.constEnd(); ++it) {
@@ -543,6 +568,16 @@
     emit scaleFChanged(d->scale);
 }
 
+void OutputDeviceInterface::setLogicalSize(const QSizeF &size)
+{
+    Q_D();
+    if (d->logicalSize == size) {
+        return;
+    }
+    d->logicalSize = size;
+    emit logicalSizeChanged();
+}
+
 QSize OutputDeviceInterface::physicalSize() const
 {
     Q_D();
@@ -591,6 +626,11 @@
     return d->scale;
 }
 
+QSizeF OutputDeviceInterface::logicalSize() const
+{
+    Q_D();
+    return d->logicalSize;
+}
 
 OutputDeviceInterface::SubPixel OutputDeviceInterface::subPixel() const
 {
diff --git a/src/server/outputmanagement_interface.cpp b/src/server/outputmanagement_interface.cpp
--- a/src/server/outputmanagement_interface.cpp
+++ b/src/server/outputmanagement_interface.cpp
@@ -56,7 +56,7 @@
     QHash<wl_resource*, OutputConfigurationInterface*> configurationInterfaces;
 };
 
-const quint32 OutputManagementInterface::Private::s_version = 2;
+const quint32 OutputManagementInterface::Private::s_version = 3;
 
 const struct org_kde_kwin_outputmanagement_interface OutputManagementInterface::Private::s_interface = {
     createConfigurationCallback