diff --git a/lib/cooked_post_processor.rb b/lib/cooked_post_processor.rb
index a6dfd642181..78591ee2548 100644
--- a/lib/cooked_post_processor.rb
+++ b/lib/cooked_post_processor.rb
@@ -426,7 +426,7 @@ class CookedPostProcessor
     informations = +"#{original_width}×#{original_height}"
     informations << " #{upload.human_filesize}" if upload
 
-    a["title"] = CGI.escapeHTML(img["title"] || filename)
+    a["title"] = CGI.escapeHTML(img["title"] || img["alt"] || filename)
 
     meta.add_child create_icon_node("far-image")
     meta.add_child create_span_node("filename", a["title"])
diff --git a/spec/components/cooked_post_processor_spec.rb b/spec/components/cooked_post_processor_spec.rb
index 174c8b0ef5e..c1870ed6b1b 100644
--- a/spec/components/cooked_post_processor_spec.rb
+++ b/spec/components/cooked_post_processor_spec.rb
@@ -597,7 +597,38 @@ describe CookedPostProcessor do
 
       end
 
-      context "with title" do
+      context "with title and alt" do
+        fab!(:post) do
+          Fabricate(:post, raw: <<~HTML)
+          <img src="#{upload.url}" title="WAT" alt="RED">
+          HTML
+        end
+
+        let(:cpp) { CookedPostProcessor.new(post, disable_loading_image: true) }
+
+        before do
+          SiteSetting.max_image_height = 2000
+          SiteSetting.create_thumbnails = true
+          FastImage.expects(:size).returns([1750, 2000])
+          OptimizedImage.expects(:resize).returns(true)
+          FileStore::BaseStore.any_instance.expects(:get_depth_for).returns(0)
+        end
+
+        it "generates overlay information using image title and ignores alt" do
+          cpp.post_process
+
+          expect(cpp.html).to match_html <<~HTML
+            <p><div class="lightbox-wrapper"><a class="lightbox" href="//test.localhost#{upload.url}" data-download-href="//test.localhost/uploads/default/#{upload.sha1}" title="WAT"><img src="//test.localhost/uploads/default/optimized/1X/#{upload.sha1}_#{OptimizedImage::VERSION}_690x788.png" title="WAT" alt="RED" width="690" height="788"><div class="meta">
+            <svg class="fa d-icon d-icon-far-image svg-icon" aria-hidden="true"><use xlink:href="#far-image"></use></svg><span class="filename">WAT</span><span class="informations">1750×2000 1.21 KB</span><svg class="fa d-icon d-icon-discourse-expand svg-icon" aria-hidden="true"><use xlink:href="#discourse-expand"></use></svg>
+            </div></a></div></p>
+          HTML
+
+          expect(cpp).to be_dirty
+        end
+
+      end
+
+      context "with title only" do
         fab!(:post) do
           Fabricate(:post, raw: <<~HTML)
           <img src="#{upload.url}" title="WAT">
@@ -614,7 +645,7 @@ describe CookedPostProcessor do
           FileStore::BaseStore.any_instance.expects(:get_depth_for).returns(0)
         end
 
-        it "generates overlay information" do
+        it "generates overlay information using image title" do
           cpp.post_process
 
           expect(cpp.html).to match_html <<~HTML
@@ -628,6 +659,37 @@ describe CookedPostProcessor do
 
       end
 
+      context "with alt only" do
+        fab!(:post) do
+          Fabricate(:post, raw: <<~HTML)
+          <img src="#{upload.url}" alt="RED">
+          HTML
+        end
+
+        let(:cpp) { CookedPostProcessor.new(post, disable_loading_image: true) }
+
+        before do
+          SiteSetting.max_image_height = 2000
+          SiteSetting.create_thumbnails = true
+          FastImage.expects(:size).returns([1750, 2000])
+          OptimizedImage.expects(:resize).returns(true)
+          FileStore::BaseStore.any_instance.expects(:get_depth_for).returns(0)
+        end
+
+        it "generates overlay information using image alt" do
+          cpp.post_process
+
+          expect(cpp.html).to match_html <<~HTML
+            <p><div class="lightbox-wrapper"><a class="lightbox" href="//test.localhost#{upload.url}" data-download-href="//test.localhost/uploads/default/#{upload.sha1}" title="RED"><img src="//test.localhost/uploads/default/optimized/1X/#{upload.sha1}_#{OptimizedImage::VERSION}_690x788.png" alt="RED" width="690" height="788"><div class="meta">
+            <svg class="fa d-icon d-icon-far-image svg-icon" aria-hidden="true"><use xlink:href="#far-image"></use></svg><span class="filename">RED</span><span class="informations">1750×2000 1.21 KB</span><svg class="fa d-icon d-icon-discourse-expand svg-icon" aria-hidden="true"><use xlink:href="#discourse-expand"></use></svg>
+            </div></a></div></p>
+          HTML
+
+          expect(cpp).to be_dirty
+        end
+
+      end
+
       context "topic image" do
         let(:post) { Fabricate(:post_with_uploaded_image) }
         let(:cpp) { CookedPostProcessor.new(post) }