diff --git a/src-ui/messages.xlf b/src-ui/messages.xlf
index d2fd2a0b1..a3e9b3330 100644
--- a/src-ui/messages.xlf
+++ b/src-ui/messages.xlf
@@ -1931,7 +1931,7 @@
         </context-group>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">688</context>
+          <context context-type="linenumber">701</context>
         </context-group>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-list/bulk-editor/bulk-editor.component.ts</context>
@@ -1970,7 +1970,7 @@
         </context-group>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">690</context>
+          <context context-type="linenumber">703</context>
         </context-group>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-list/bulk-editor/bulk-editor.component.ts</context>
@@ -2394,13 +2394,6 @@
           <context context-type="linenumber">63</context>
         </context-group>
       </trans-unit>
-      <trans-unit id="5000042972069710005" datatype="html">
-        <source><x id="START_TAG_SPAN" ctype="x-span" equiv-text="&lt;span class=&quot;d-inline-block&quot; style=&quot;padding-bottom: 1px;&quot; &gt;"/>Cancel<x id="CLOSE_TAG_SPAN" ctype="x-span" equiv-text="&lt;/span&gt;"/></source>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/common/confirm-dialog/confirm-dialog.component.html</context>
-          <context context-type="linenumber">16</context>
-        </context-group>
-      </trans-unit>
       <trans-unit id="1234709746630139322" datatype="html">
         <source>Confirmation</source>
         <context-group purpose="location">
@@ -2435,6 +2428,73 @@
           <context context-type="linenumber">439</context>
         </context-group>
       </trans-unit>
+      <trans-unit id="2159130950882492111" datatype="html">
+        <source>Cancel</source>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/common/confirm-dialog/confirm-dialog.component.ts</context>
+          <context context-type="linenumber">44</context>
+        </context-group>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/common/edit-dialog/correspondent-edit-dialog/correspondent-edit-dialog.component.html</context>
+          <context context-type="linenumber">24</context>
+        </context-group>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/common/edit-dialog/custom-field-edit-dialog/custom-field-edit-dialog.component.html</context>
+          <context context-type="linenumber">15</context>
+        </context-group>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/common/edit-dialog/document-type-edit-dialog/document-type-edit-dialog.component.html</context>
+          <context context-type="linenumber">26</context>
+        </context-group>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/common/edit-dialog/group-edit-dialog/group-edit-dialog.component.html</context>
+          <context context-type="linenumber">16</context>
+        </context-group>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/common/edit-dialog/mail-account-edit-dialog/mail-account-edit-dialog.component.html</context>
+          <context context-type="linenumber">36</context>
+        </context-group>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/common/edit-dialog/mail-rule-edit-dialog/mail-rule-edit-dialog.component.html</context>
+          <context context-type="linenumber">48</context>
+        </context-group>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/common/edit-dialog/storage-path-edit-dialog/storage-path-edit-dialog.component.html</context>
+          <context context-type="linenumber">25</context>
+        </context-group>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/common/edit-dialog/tag-edit-dialog/tag-edit-dialog.component.html</context>
+          <context context-type="linenumber">27</context>
+        </context-group>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/common/edit-dialog/user-edit-dialog/user-edit-dialog.component.html</context>
+          <context context-type="linenumber">35</context>
+        </context-group>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/common/edit-dialog/workflow-edit-dialog/workflow-edit-dialog.component.html</context>
+          <context context-type="linenumber">170</context>
+        </context-group>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/common/permissions-dialog/permissions-dialog.component.html</context>
+          <context context-type="linenumber">22</context>
+        </context-group>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/common/profile-edit-dialog/profile-edit-dialog.component.html</context>
+          <context context-type="linenumber">57</context>
+        </context-group>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/common/select-dialog/select-dialog.component.html</context>
+          <context context-type="linenumber">12</context>
+        </context-group>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/document-list/bulk-editor/bulk-editor.component.html</context>
+          <context context-type="linenumber">6</context>
+        </context-group>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/document-list/save-view-config-dialog/save-view-config-dialog.component.html</context>
+          <context context-type="linenumber">20</context>
+        </context-group>
+      </trans-unit>
       <trans-unit id="3972154626835212608" datatype="html">
         <source>Create New Field</source>
         <context-group purpose="location">
@@ -2599,69 +2659,6 @@
           <context context-type="linenumber">194</context>
         </context-group>
       </trans-unit>
-      <trans-unit id="2159130950882492111" datatype="html">
-        <source>Cancel</source>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/common/edit-dialog/correspondent-edit-dialog/correspondent-edit-dialog.component.html</context>
-          <context context-type="linenumber">24</context>
-        </context-group>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/common/edit-dialog/custom-field-edit-dialog/custom-field-edit-dialog.component.html</context>
-          <context context-type="linenumber">15</context>
-        </context-group>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/common/edit-dialog/document-type-edit-dialog/document-type-edit-dialog.component.html</context>
-          <context context-type="linenumber">26</context>
-        </context-group>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/common/edit-dialog/group-edit-dialog/group-edit-dialog.component.html</context>
-          <context context-type="linenumber">16</context>
-        </context-group>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/common/edit-dialog/mail-account-edit-dialog/mail-account-edit-dialog.component.html</context>
-          <context context-type="linenumber">36</context>
-        </context-group>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/common/edit-dialog/mail-rule-edit-dialog/mail-rule-edit-dialog.component.html</context>
-          <context context-type="linenumber">48</context>
-        </context-group>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/common/edit-dialog/storage-path-edit-dialog/storage-path-edit-dialog.component.html</context>
-          <context context-type="linenumber">25</context>
-        </context-group>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/common/edit-dialog/tag-edit-dialog/tag-edit-dialog.component.html</context>
-          <context context-type="linenumber">27</context>
-        </context-group>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/common/edit-dialog/user-edit-dialog/user-edit-dialog.component.html</context>
-          <context context-type="linenumber">35</context>
-        </context-group>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/common/edit-dialog/workflow-edit-dialog/workflow-edit-dialog.component.html</context>
-          <context context-type="linenumber">170</context>
-        </context-group>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/common/permissions-dialog/permissions-dialog.component.html</context>
-          <context context-type="linenumber">22</context>
-        </context-group>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/common/profile-edit-dialog/profile-edit-dialog.component.html</context>
-          <context context-type="linenumber">57</context>
-        </context-group>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/common/select-dialog/select-dialog.component.html</context>
-          <context context-type="linenumber">12</context>
-        </context-group>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/document-list/bulk-editor/bulk-editor.component.html</context>
-          <context context-type="linenumber">6</context>
-        </context-group>
-        <context-group purpose="location">
-          <context context-type="sourcefile">src/app/components/document-list/save-view-config-dialog/save-view-config-dialog.component.html</context>
-          <context context-type="linenumber">20</context>
-        </context-group>
-      </trans-unit>
       <trans-unit id="6457471243969293847" datatype="html">
         <source>Create new correspondent</source>
         <context-group purpose="location">
@@ -4793,47 +4790,75 @@
           <context context-type="linenumber">276,278</context>
         </context-group>
       </trans-unit>
+      <trans-unit id="3200733026060976258" datatype="html">
+        <source>Document changes detected</source>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
+          <context context-type="linenumber">298</context>
+        </context-group>
+      </trans-unit>
+      <trans-unit id="2887155916749964" datatype="html">
+        <source>The version of this document in your browser session appears older than the existing version.</source>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
+          <context context-type="linenumber">299</context>
+        </context-group>
+      </trans-unit>
+      <trans-unit id="237142428785956348" datatype="html">
+        <source>Saving the document here may overwrite other changes that were made. To restore the existing version, discard your changes or close the document.</source>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
+          <context context-type="linenumber">300</context>
+        </context-group>
+      </trans-unit>
+      <trans-unit id="8720977247725652816" datatype="html">
+        <source>Ok</source>
+        <context-group purpose="location">
+          <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
+          <context context-type="linenumber">301</context>
+        </context-group>
+      </trans-unit>
       <trans-unit id="5758784066858623886" datatype="html">
         <source>Error retrieving metadata</source>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">424</context>
+          <context context-type="linenumber">437</context>
         </context-group>
       </trans-unit>
       <trans-unit id="3456881259945295697" datatype="html">
         <source>Error retrieving suggestions.</source>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">445</context>
+          <context context-type="linenumber">458</context>
         </context-group>
       </trans-unit>
       <trans-unit id="8348337312757497317" datatype="html">
         <source>Document saved successfully.</source>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">563</context>
+          <context context-type="linenumber">576</context>
         </context-group>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">572</context>
+          <context context-type="linenumber">585</context>
         </context-group>
       </trans-unit>
       <trans-unit id="448882439049417053" datatype="html">
         <source>Error saving document</source>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">576</context>
+          <context context-type="linenumber">589</context>
         </context-group>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">617</context>
+          <context context-type="linenumber">630</context>
         </context-group>
       </trans-unit>
       <trans-unit id="9021887951960049161" datatype="html">
         <source>Confirm delete</source>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">643</context>
+          <context context-type="linenumber">656</context>
         </context-group>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/manage/management-list/management-list.component.ts</context>
@@ -4844,35 +4869,35 @@
         <source>Do you really want to delete document &quot;<x id="PH" equiv-text="this.document.title"/>&quot;?</source>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">644</context>
+          <context context-type="linenumber">657</context>
         </context-group>
       </trans-unit>
       <trans-unit id="6691075929777935948" datatype="html">
         <source>The files for this document will be deleted permanently. This operation cannot be undone.</source>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">645</context>
+          <context context-type="linenumber">658</context>
         </context-group>
       </trans-unit>
       <trans-unit id="719892092227206532" datatype="html">
         <source>Delete document</source>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">647</context>
+          <context context-type="linenumber">660</context>
         </context-group>
       </trans-unit>
       <trans-unit id="7295637485862454066" datatype="html">
         <source>Error deleting document</source>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">666</context>
+          <context context-type="linenumber">679</context>
         </context-group>
       </trans-unit>
       <trans-unit id="7362691899087997122" datatype="html">
         <source>Redo OCR confirm</source>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">686</context>
+          <context context-type="linenumber">699</context>
         </context-group>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-list/bulk-editor/bulk-editor.component.ts</context>
@@ -4883,28 +4908,28 @@
         <source>This operation will permanently redo OCR for this document.</source>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">687</context>
+          <context context-type="linenumber">700</context>
         </context-group>
       </trans-unit>
       <trans-unit id="5729001209753056399" datatype="html">
         <source>Redo OCR operation will begin in the background. Close and re-open or reload this document after the operation has completed to see new content.</source>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">698</context>
+          <context context-type="linenumber">711</context>
         </context-group>
       </trans-unit>
       <trans-unit id="4409560272830824468" datatype="html">
         <source>Error executing operation</source>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">709</context>
+          <context context-type="linenumber">722</context>
         </context-group>
       </trans-unit>
       <trans-unit id="4458954481601077369" datatype="html">
         <source>Page Fit</source>
         <context-group purpose="location">
           <context context-type="sourcefile">src/app/components/document-detail/document-detail.component.ts</context>
-          <context context-type="linenumber">778</context>
+          <context context-type="linenumber">791</context>
         </context-group>
       </trans-unit>
       <trans-unit id="6857598786757174736" datatype="html">
diff --git a/src-ui/src/app/components/common/confirm-dialog/confirm-dialog.component.html b/src-ui/src/app/components/common/confirm-dialog/confirm-dialog.component.html
index bb5577061..e25ace612 100644
--- a/src-ui/src/app/components/common/confirm-dialog/confirm-dialog.component.html
+++ b/src-ui/src/app/components/common/confirm-dialog/confirm-dialog.component.html
@@ -12,8 +12,8 @@
   }
 </div>
 <div class="modal-footer">
-  <button type="button" class="btn btn-outline-secondary" (click)="cancel()" [disabled]="!buttonsEnabled" i18n>
-        <span class="d-inline-block" style="padding-bottom: 1px;" >Cancel</span>
+  <button type="button" class="btn" [class]="cancelBtnClass" (click)="cancel()" [disabled]="!buttonsEnabled">
+        <span class="d-inline-block" style="padding-bottom: 1px;">{{cancelBtnCaption}}</span>
       </button>
   <button type="button" class="btn" [class]="btnClass" (click)="confirm()" [disabled]="!confirmButtonEnabled || !buttonsEnabled">
     <span>
diff --git a/src-ui/src/app/components/common/confirm-dialog/confirm-dialog.component.ts b/src-ui/src/app/components/common/confirm-dialog/confirm-dialog.component.ts
index 4ab2af257..9c627ead0 100644
--- a/src-ui/src/app/components/common/confirm-dialog/confirm-dialog.component.ts
+++ b/src-ui/src/app/components/common/confirm-dialog/confirm-dialog.component.ts
@@ -37,6 +37,12 @@ export class ConfirmDialogComponent {
   @Input()
   alternativeBtnCaption
 
+  @Input()
+  cancelBtnClass = 'btn-outline-secondary'
+
+  @Input()
+  cancelBtnCaption = $localize`Cancel`
+
   @Input()
   buttonsEnabled = true
 
diff --git a/src-ui/src/app/components/document-detail/document-detail.component.spec.ts b/src-ui/src/app/components/document-detail/document-detail.component.spec.ts
index d37fa852a..1492c3e0e 100644
--- a/src-ui/src/app/components/document-detail/document-detail.component.spec.ts
+++ b/src-ui/src/app/components/document-detail/document-detail.component.spec.ts
@@ -79,8 +79,9 @@ const doc: Document = {
   storage_path: 31,
   tags: [41, 42, 43],
   content: 'text content',
-  added: new Date(),
-  created: new Date(),
+  added: new Date('May 4, 2014 03:24:00'),
+  created: new Date('May 4, 2014 03:24:00'),
+  modified: new Date('May 4, 2014 03:24:00'),
   archive_serial_number: null,
   original_file_name: 'file.pdf',
   owner: null,
@@ -935,6 +936,26 @@ describe('DocumentDetailComponent', () => {
     expect(refreshSpy).toHaveBeenCalled()
   })
 
+  it('should warn when open document does not match doc retrieved from backend on init', () => {
+    const modalSpy = jest.spyOn(modalService, 'open')
+    const openDoc = Object.assign({}, doc)
+    // simulate a document being modified elsewhere and db updated
+    doc.modified = new Date()
+    jest.spyOn(documentService, 'get').mockReturnValueOnce(of(doc))
+    jest.spyOn(openDocumentsService, 'getOpenDocument').mockReturnValue(openDoc)
+    jest.spyOn(customFieldsService, 'listAll').mockReturnValue(
+      of({
+        count: customFields.length,
+        all: customFields.map((f) => f.id),
+        results: customFields,
+      })
+    )
+    fixture.detectChanges() // calls ngOnInit
+    expect(modalSpy).toHaveBeenCalledWith(ConfirmDialogComponent, {
+      backdrop: 'static',
+    })
+  })
+
   function initNormally() {
     jest
       .spyOn(documentService, 'get')
diff --git a/src-ui/src/app/components/document-detail/document-detail.component.ts b/src-ui/src/app/components/document-detail/document-detail.component.ts
index edc19ec70..83057b8cd 100644
--- a/src-ui/src/app/components/document-detail/document-detail.component.ts
+++ b/src-ui/src/app/components/document-detail/document-detail.component.ts
@@ -289,7 +289,23 @@ export class DocumentDetailComponent
           const openDocument = this.openDocumentService.getOpenDocument(
             this.documentId
           )
+
           if (openDocument) {
+            if (
+              new Date(doc.modified) > new Date(openDocument.modified) &&
+              !this.modalService.hasOpenModals()
+            ) {
+              let modal = this.modalService.open(ConfirmDialogComponent, {
+                backdrop: 'static',
+              })
+              modal.componentInstance.title = $localize`Document changes detected`
+              modal.componentInstance.messageBold = $localize`The version of this document in your browser session appears older than the existing version.`
+              modal.componentInstance.message = $localize`Saving the document here may overwrite other changes that were made. To restore the existing version, discard your changes or close the document.`
+              modal.componentInstance.cancelBtnCaption = $localize`Ok`
+              modal.componentInstance.cancelBtnClass = 'btn-primary'
+              modal.componentInstance.btnClass = 'visually-hidden'
+            }
+
             if (this.documentForm.dirty) {
               Object.assign(openDocument, this.documentForm.value)
               openDocument['owner'] =
diff --git a/src/documents/serialisers.py b/src/documents/serialisers.py
index ffcfbcc1d..34d842443 100644
--- a/src/documents/serialisers.py
+++ b/src/documents/serialisers.py
@@ -13,6 +13,7 @@ from django.contrib.contenttypes.models import ContentType
 from django.core.validators import DecimalValidator
 from django.core.validators import MaxLengthValidator
 from django.core.validators import integer_validator
+from django.utils import timezone
 from django.utils.crypto import get_random_string
 from django.utils.text import slugify
 from django.utils.translation import gettext as _
@@ -580,6 +581,7 @@ class CustomFieldInstanceSerializer(serializers.ModelSerializer):
             custom_field_instances_to_update,
             ["value_document_ids"],
         )
+        Document.objects.filter(id__in=target_doc_ids).update(modified=timezone.now())
 
     @staticmethod
     def remove_doclink(
@@ -600,6 +602,7 @@ class CustomFieldInstanceSerializer(serializers.ModelSerializer):
         ):
             target_doc_field_instance.value.remove(document.id)
             target_doc_field_instance.save()
+        Document.objects.filter(id=target_doc_id).update(modified=timezone.now())
 
     class Meta:
         model = CustomFieldInstance