diff --git a/theme/boost/scss/moodle/calendar.scss b/theme/boost/scss/moodle/calendar.scss
index 84bfb8e3697..93ac8e92005 100644
--- a/theme/boost/scss/moodle/calendar.scss
+++ b/theme/boost/scss/moodle/calendar.scss
@@ -736,4 +736,5 @@ table.calendartable caption {
 
 .cal_courses_flt {
     color: $gray-600;
+    max-width: 75%;
 }
diff --git a/theme/boost/scss/moodle/core.scss b/theme/boost/scss/moodle/core.scss
index c9731ca9bbe..dff273e447e 100644
--- a/theme/boost/scss/moodle/core.scss
+++ b/theme/boost/scss/moodle/core.scss
@@ -2577,6 +2577,7 @@ input[disabled] {
 
 .custom-select {
     width: auto;
+    max-width: 100%;
 }
 
 .fade.in {
@@ -3023,3 +3024,17 @@ body.dragging {
         }
     }
 }
+
+/** Prevent long strings exceeding page width */
+.page-header-headings,
+.coursename,
+.categoryname,
+.breadcrumb-item,
+.dropdown-item {
+
+    &:not(.text-truncate) {
+        word-break: normal;
+        overflow-wrap: anywhere;
+        white-space: normal;
+    }
+}
diff --git a/theme/boost/style/moodle.css b/theme/boost/style/moodle.css
index 5c104f90a75..fd84b79f587 100644
--- a/theme/boost/style/moodle.css
+++ b/theme/boost/style/moodle.css
@@ -11943,7 +11943,8 @@ input[disabled] {
   cursor: not-allowed; }
 
 .custom-select {
-  width: auto; }
+  width: auto;
+  max-width: 100%; }
 
 .fade.in {
   opacity: 1; }
@@ -12321,6 +12322,16 @@ body.dragging .dragging {
   border-top-right-radius: 0.2rem;
   border-bottom-right-radius: 0.2rem; }
 
+/** Prevent long strings exceeding page width */
+.page-header-headings:not(.text-truncate),
+.coursename:not(.text-truncate),
+.categoryname:not(.text-truncate),
+.breadcrumb-item:not(.text-truncate),
+.dropdown-item:not(.text-truncate) {
+  word-break: normal;
+  overflow-wrap: anywhere;
+  white-space: normal; }
+
 .icon {
   font-size: 16px;
   width: 16px;
@@ -13727,7 +13738,8 @@ table.calendartable caption {
     margin: 0; }
 
 .cal_courses_flt {
-  color: #6a737b; }
+  color: #6a737b;
+  max-width: 75%; }
 
 .content-bank-container .cb-content-wrapper {
   padding: 0.5rem;
diff --git a/theme/classic/style/moodle.css b/theme/classic/style/moodle.css
index 79abfae5890..2e3789e9e81 100644
--- a/theme/classic/style/moodle.css
+++ b/theme/classic/style/moodle.css
@@ -11943,7 +11943,8 @@ input[disabled] {
   cursor: not-allowed; }
 
 .custom-select {
-  width: auto; }
+  width: auto;
+  max-width: 100%; }
 
 .fade.in {
   opacity: 1; }
@@ -12321,6 +12322,16 @@ body.dragging .dragging {
   border-top-right-radius: 0.2rem;
   border-bottom-right-radius: 0.2rem; }
 
+/** Prevent long strings exceeding page width */
+.page-header-headings:not(.text-truncate),
+.coursename:not(.text-truncate),
+.categoryname:not(.text-truncate),
+.breadcrumb-item:not(.text-truncate),
+.dropdown-item:not(.text-truncate) {
+  word-break: normal;
+  overflow-wrap: anywhere;
+  white-space: normal; }
+
 .icon {
   font-size: 16px;
   width: 16px;
@@ -13727,7 +13738,8 @@ table.calendartable caption {
     margin: 0; }
 
 .cal_courses_flt {
-  color: #6a737b; }
+  color: #6a737b;
+  max-width: 75%; }
 
 .content-bank-container .cb-content-wrapper {
   padding: 0.5rem;