diff --git a/app/controllers/api/templates_controller.rb b/app/controllers/api/templates_controller.rb
index e32b103e78..1b93ed1782 100644
--- a/app/controllers/api/templates_controller.rb
+++ b/app/controllers/api/templates_controller.rb
@@ -121,29 +121,22 @@ def pdf
     def process_documents(template, documents_params)
       return [] if documents_params.blank?
 
-      documents_params.map.with_index do |doc_param, _index|
-        (doc_param[:file].length / 4.0 * 3).ceil
-        # Validate base64 string
+      documents_params.map do |doc_param|
         raise ArgumentError, 'Invalid base64 string format' unless doc_param[:file].match?(%r{\A[A-Za-z0-9+/]*={0,2}\z})
 
-        # Decode base64 file data
         file_data = Base64.decode64(doc_param[:file])
+        detected = Marcel::MimeType.for(StringIO.new(file_data), name: doc_param[:name])
+        content_type = detected.to_s.start_with?('image/') ? detected : 'application/pdf'
 
-        # Check if the decoded data looks like a PDF
-        file_data[0..3] if file_data.size >= 4
-
-        # Create a temporary file-like object
         file = Tempfile.new(['document', '.pdf'])
         file.binmode
         file.write(file_data)
         file.rewind
 
-        # Add original filename
         file.define_singleton_method(:original_filename) { doc_param[:name] }
-        file.define_singleton_method(:content_type) { 'application/pdf' }
+        file.define_singleton_method(:content_type) { content_type }
 
-        result = Templates::CreateAttachments.handle_pdf_or_image(template, file, file_data, {}, extract_fields: true)
-        result
+        Templates::CreateAttachments.handle_pdf_or_image(template, file, file_data, {}, extract_fields: true)
       ensure
         file&.close
         file&.unlink
diff --git a/spec/requests/templates_spec.rb b/spec/requests/templates_spec.rb
index da585858b8..72a56d3406 100644
--- a/spec/requests/templates_spec.rb
+++ b/spec/requests/templates_spec.rb
@@ -227,6 +227,65 @@
       stored_field = Template.last.fields.find { |f| f['name'] == 'First Name' }
       expect(stored_field['prefill']).to eq('employee_first_name')
     end
+
+    it 'creates a template from a PNG document' do
+      png_base64 = Base64.strict_encode64(Rails.root.join('spec/fixtures/sample-image.png').binread)
+
+      post '/api/templates/pdf',
+           headers: { 'x-auth-token': author.access_token.token },
+           params: {
+             name: 'Image Template',
+             documents: [{ name: 'sample-image.png', file: png_base64 }]
+           }.to_json,
+           env: { 'CONTENT_TYPE' => 'application/json' }
+
+      expect(response).to have_http_status(:ok)
+
+      document = Template.last.documents.first
+      expect(document.content_type).to eq('image/png')
+      expect(document.preview_images).to be_present
+    end
+
+    it 'creates a template from a JPEG document' do
+      jpeg_data = Vips::Image.new_from_file(Rails.root.join('spec/fixtures/sample-image.png').to_s)
+                             .write_to_buffer('.jpg')
+
+      post '/api/templates/pdf',
+           headers: { 'x-auth-token': author.access_token.token },
+           params: {
+             name: 'Jpeg Template',
+             documents: [{ name: 'sample-image.jpg', file: Base64.strict_encode64(jpeg_data) }]
+           }.to_json,
+           env: { 'CONTENT_TYPE' => 'application/json' }
+
+      expect(response).to have_http_status(:ok)
+      expect(Template.last.documents.first.content_type).to eq('image/jpeg')
+    end
+
+    it 'detects a PNG even when the document name ends in .pdf' do
+      png_base64 = Base64.strict_encode64(Rails.root.join('spec/fixtures/sample-image.png').binread)
+
+      post '/api/templates/pdf',
+           headers: { 'x-auth-token': author.access_token.token },
+           params: base_params.merge(documents: [{ name: 'scan.pdf', file: png_base64 }]).to_json,
+           env: { 'CONTENT_TYPE' => 'application/json' }
+
+      expect(response).to have_http_status(:ok)
+      expect(Template.last.documents.first.content_type).to eq('image/png')
+    end
+
+    it 'returns the existing error for a document that is not a PDF or image' do
+      post '/api/templates/pdf',
+           headers: { 'x-auth-token': author.access_token.token },
+           params: {
+             name: 'Bad Template',
+             documents: [{ name: 'notes.txt', file: Base64.strict_encode64('not a real file') }]
+           }.to_json,
+           env: { 'CONTENT_TYPE' => 'application/json' }
+
+      expect(response).to have_http_status(:unprocessable_entity)
+      expect(response.parsed_body['error']).to eq('Unable to create template')
+    end
   end
 
   describe 'POST /api/templates/:id/clone' do