diff --git a/deepcave/plugins/objective/cost_over_time.py b/deepcave/plugins/objective/cost_over_time.py
index a4fbd30d..c505d5cb 100644
--- a/deepcave/plugins/objective/cost_over_time.py
+++ b/deepcave/plugins/objective/cost_over_time.py
@@ -6,9 +6,10 @@
 from dash import dcc, html
 from dash.exceptions import PreventUpdate
 
-from deepcave import config
+from deepcave import config, notification
 from deepcave.plugins.dynamic import DynamicPlugin
 from deepcave.runs import AbstractRun, check_equality
+from deepcave.runs.exceptions import NotMergeableError, RunInequality
 from deepcave.utils.layout import get_select_options, help_button
 from deepcave.utils.styled_plotty import (
     get_color,
@@ -24,8 +25,19 @@ class CostOverTime(DynamicPlugin):
     help = "docs/plugins/cost_over_time.rst"
 
     def check_runs_compatibility(self, runs: List[AbstractRun]) -> None:
-        check_equality(runs, objectives=True, budgets=True)
-
+        try:
+            check_equality(runs, objectives=True, budgets=True)
+        except NotMergeableError as e:
+            run_inequality = e.args[1]
+            if run_inequality == RunInequality.INEQ_BUDGET:
+                notification.update("The budgets of the runs are not equal.", color="warning")
+            elif run_inequality == RunInequality.INEQ_CONFIGSPACE:
+                notification.update("The configuration spaces of the runs are not equal.", color="warning")
+            elif run_inequality == RunInequality.INEQ_META:
+                notification.update("The meta data of the runs is not equal.", color="warning")
+            elif run_inequality == RunInequality.INEQ_OBJECTIVE:
+                notification.update("The objectives of the runs are not equal.", color="warning")
+        
         # Set some attributes here
         run = runs[0]
 
diff --git a/deepcave/plugins/objective/pareto_front.py b/deepcave/plugins/objective/pareto_front.py
index 17e55a39..7b148115 100644
--- a/deepcave/plugins/objective/pareto_front.py
+++ b/deepcave/plugins/objective/pareto_front.py
@@ -5,9 +5,10 @@
 import plotly.graph_objs as go
 from dash import dcc, html
 
-from deepcave import config
+from deepcave import config, notification
 from deepcave.plugins.dynamic import DynamicPlugin
 from deepcave.runs import Status, check_equality
+from deepcave.runs.exceptions import NotMergeableError, RunInequality
 from deepcave.utils.layout import get_select_options, help_button
 from deepcave.utils.styled_plot import plt
 from deepcave.utils.styled_plotty import (
@@ -24,7 +25,18 @@ class ParetoFront(DynamicPlugin):
     help = "docs/plugins/pareto_front.rst"
 
     def check_runs_compatibility(self, runs):
-        check_equality(runs, objectives=True, budgets=True)
+        try:
+            check_equality(runs, objectives=True, budgets=True)
+        except NotMergeableError as e:
+            run_inequality = e.args[1]
+            if run_inequality == RunInequality.INEQ_BUDGET:
+                notification.update("The budgets of the runs are not equal.", color="warning")
+            elif run_inequality == RunInequality.INEQ_CONFIGSPACE:
+                notification.update("The configuration spaces of the runs are not equal.", color="warning")
+            elif run_inequality == RunInequality.INEQ_META:
+                notification.update("The meta data of the runs is not equal.", color="warning")
+            elif run_inequality == RunInequality.INEQ_OBJECTIVE:
+                notification.update("The objectives of the runs are not equal.", color="warning")
 
         # Set some attributes here
         run = runs[0]
diff --git a/deepcave/runs/__init__.py b/deepcave/runs/__init__.py
index 7443f84f..fb69b3ad 100644
--- a/deepcave/runs/__init__.py
+++ b/deepcave/runs/__init__.py
@@ -20,7 +20,7 @@
     CONSTANT_VALUE,
     NAN_VALUE,
 )
-from deepcave.runs.exceptions import NotMergeableError
+from deepcave.runs.exceptions import NotMergeableError, RunInequality
 from deepcave.runs.objective import Objective
 from deepcave.runs.status import Status
 from deepcave.runs.trial import Trial
@@ -919,6 +919,7 @@ def check_equality(
     Dict[str, Any]
         Dictionary containing the checked attributes.
     """
+
     result = {}
 
     if len(runs) == 0:
@@ -938,7 +939,7 @@ def check_equality(
                     continue
 
                 if k not in m2 or m2[k] != v:
-                    raise NotMergeableError("Meta data of runs are not equal.")
+                    raise NotMergeableError("Meta data of runs are not equal.", RunInequality.INEQ_META)
 
         result["meta"] = m1
 
@@ -950,7 +951,7 @@ def check_equality(
         for run in runs:
             cs2 = run.configspace
             if cs1 != cs2:
-                raise NotMergeableError("Configspace of runs are not equal.")
+                raise NotMergeableError("Configspace of runs are not equal.", RunInequality.INEQ_CONFIGSPACE)
 
         result["configspace"] = cs1
 
@@ -960,7 +961,7 @@ def check_equality(
         for run in runs:
             b2 = run.get_budgets(include_combined=False)
             if b1 != b2:
-                raise NotMergeableError("Budgets of runs are not equal.")
+                raise NotMergeableError("Budgets of runs are not equal.", RunInequality.INEQ_BUDGET)
 
         result["budgets"] = b1
         if meta:
@@ -977,7 +978,7 @@ def check_equality(
                 continue
 
             if len(o1) != len(o2):
-                raise NotMergeableError("Objectives of runs are not equal.")
+                raise NotMergeableError("Objectives of runs are not equal.", RunInequality.INEQ_OBJECTIVE)
 
             for o1_, o2_ in zip(o1, o2):
                 o1_.merge(o2_)
@@ -987,4 +988,4 @@ def check_equality(
         if meta:
             result["meta"]["objectives"] = serialized_objectives
 
-    return result
+    return result
\ No newline at end of file
diff --git a/deepcave/runs/exceptions.py b/deepcave/runs/exceptions.py
index aefe3a20..14cd2ec3 100644
--- a/deepcave/runs/exceptions.py
+++ b/deepcave/runs/exceptions.py
@@ -1,3 +1,4 @@
+from enum import Enum
 class NotValidRunError(Exception):
     """Raised if directory is not a valid run."""
 
@@ -8,3 +9,13 @@ class NotMergeableError(Exception):
     """Raised if two or more runs are not mergeable"""
 
     pass
+
+class RunInequality(Enum):
+    """Check why runs were not compatible."""
+    INEQ_META = 1
+    INEQ_OBJECTIVE = 2
+    INEQ_BUDGET = 3
+    INEQ_CONFIGSPACE = 4
+
+
+