diff --git a/pdelfin/eval/evalhtml.py b/pdelfin/eval/evalhtml.py
index 17cec53..6dcc0c3 100644
--- a/pdelfin/eval/evalhtml.py
+++ b/pdelfin/eval/evalhtml.py
@@ -1,70 +1,88 @@
-from concurrent.futures import ThreadPoolExecutor, as_completed
-from jinja2 import Template
-import random
 import os
-import subprocess
+import random
 import tempfile
 import boto3
-import base64
-import io
-
+from concurrent.futures import ThreadPoolExecutor
+from jinja2 import Template
 from urllib.parse import urlparse
-from PIL import Image
+from difflib import SequenceMatcher
 from tqdm import tqdm
-
 from pdelfin.silver_data.renderpdf import render_pdf_to_base64png
 
 session = boto3.Session(profile_name='s2')
 s3_client = session.client('s3')
 
+def generate_diff_html(a, b):
+    """
+    Generates HTML with differences between strings a and b.
+    Additions in 'b' are highlighted in green, deletions from 'a' are highlighted in red.
+    """
+    seq_matcher = SequenceMatcher(None, a, b)
+    output_html = ""
+    for opcode, a0, a1, b0, b1 in seq_matcher.get_opcodes():
+        if opcode == 'equal':
+            output_html += a[a0:a1]
+        elif opcode == 'insert':
+            output_html += f"<span class='added'>{b[b0:b1]}</span>"
+        elif opcode == 'delete':
+            output_html += f"<span class='removed'>{a[a0:a1]}</span>"
+        elif opcode == 'replace':
+            output_html += f"<span class='removed'>{a[a0:a1]}</span><span class='added'>{b[b0:b1]}</span>"
+    return output_html
 
 def process_entry(i, entry):
     # Randomly decide whether to display gold on the left or right
     if random.choice([True, False]):
         left_text, right_text = entry["gold_text"], entry["eval_text"]
-        left_alignment, right_alignment = entry["alignment"], entry["alignment"]
         left_class, right_class = "gold", "eval"
     else:
         left_text, right_text = entry["eval_text"], entry["gold_text"]
-        left_alignment, right_alignment = entry["alignment"], entry["alignment"]
         left_class, right_class = "eval", "gold"
 
-    # Convert newlines to <p> tags for proper formatting
+    # Generate diff for right_text compared to left_text
+    diff_html = generate_diff_html(left_text, right_text)
+
     left_text = "<p>" + left_text.replace("\n", "</p><p>") + "</p>"
     right_text = "<p>" + right_text.replace("\n", "</p><p>") + "</p>"
+    diff_html = "<p>" + diff_html.replace("\n", "</p><p>") + "</p>"
 
     parsed_url = urlparse(entry["s3_path"])
     bucket = parsed_url.netloc
     s3_key = parsed_url.path.lstrip('/')
-    signed_pdf_link = s3_client.generate_presigned_url("get_object", Params={"Bucket": bucket, "Key": s3_key}, ExpiresIn=604800)
+    signed_pdf_link = s3_client.generate_presigned_url(
+        "get_object",
+        Params={"Bucket": bucket, "Key": s3_key},
+        ExpiresIn=604800
+    )
 
     with tempfile.NamedTemporaryFile(suffix=".pdf", delete=False) as tmp_pdf:
         pdf_path = tmp_pdf.name
         bucket, key = entry["s3_path"].replace("s3://", "").split('/', 1)
         s3_client.download_file(bucket, key, pdf_path)
-        
-        page_image_base64 = render_pdf_to_base64png(tmp_pdf.name, entry["page"], target_longest_image_dim=1024)
+        page_image_base64 = render_pdf_to_base64png(
+            tmp_pdf.name, entry["page"], target_longest_image_dim=1024
+        )
 
     return {
         "entry_id": i,
         "page_image": page_image_base64,
         "s3_path": entry["s3_path"],
         "page": entry["page"],
+        "alignment": entry["alignment"],
         "signed_pdf_link": signed_pdf_link,
         "left_text": left_text,
         "right_text": right_text,
-        "left_alignment": left_alignment,
-        "right_alignment": right_alignment,
+        "diff_text": diff_html, 
         "left_class": left_class,
         "right_class": right_class,
         "gold_class": "gold" if left_class == "gold" else "eval",
         "eval_class": "eval" if right_class == "eval" else "gold"
     }
 
-
 def create_review_html(data, filename="review_page.html"):
     # Load the Jinja2 template from the file
-    with open(os.path.join(os.path.dirname(__file__), "evalhtml_template.html"), "r") as f:
+    template_path = os.path.join(os.path.dirname(__file__), "evalhtml_template.html")
+    with open(template_path, "r") as f:
         template = Template(f.read())
 
     entries = []
diff --git a/pdelfin/eval/evalhtml_template.html b/pdelfin/eval/evalhtml_template.html
index 9b0e319..9c79039 100644
--- a/pdelfin/eval/evalhtml_template.html
+++ b/pdelfin/eval/evalhtml_template.html
@@ -41,6 +41,7 @@
             flex-direction: column;
             justify-content: space-between;
             cursor: pointer;
+            position: relative;
         }
         .text-block:hover {
             background-color: #e0e0e0;
@@ -159,6 +160,25 @@
         .voting-buttons button.selected {
             border: 3px solid #000;
         }
+        /* for diffs */
+        .added {
+            background-color: #d4fcdc;
+        }
+        .removed {
+            background-color: #fcd4d4;
+            text-decoration: line-through;
+        }
+
+        /* Diff Toggle Styles */
+        body.diffed .right-text {
+            display: none;
+        }
+        body.diffed .diff-text {
+            display: block;
+        }
+        .diff-text {
+            display: none;
+        }
     </style>
 </head>
 <body>
@@ -166,8 +186,15 @@
 
     <!-- Floating Reveal Box -->
     <div class="reveal-box">
-        <input type="checkbox" id="reveal-toggle" />
-        <label for="reveal-toggle">Reveal Gold/Eval</label>
+        <div>
+            <input type="checkbox" id="diff-toggle" />
+            <label for="diff-toggle">Toggle diff</label>
+        </div>
+
+        <div>
+            <input type="checkbox" id="reveal-toggle" />
+            <label for="reveal-toggle">Reveal Gold/Eval</label>
+        </div>
         <div class="reveal-info" id="vote-info">Votes</div>
     </div>
 
@@ -177,7 +204,7 @@
             <div class="image-container">
                 <img src="data:image/png;base64,{{ entry.page_image }}" alt="Render">
 
-                <div class="alignment">Alignment: {{ entry.left_alignment }}</div>
+                <div class="alignment">Alignment: {{ entry.alignment }}</div>
                 <a href="{{entry.signed_pdf_link}}#page={{ entry.page }}" target="_blank">{{ entry.s3_path }} (Page {{ entry.page }})</a>
                 
                 <!-- Voting Buttons -->
@@ -190,8 +217,10 @@
             <div class="text-block {{ entry.left_class }}" data-choice="left">
                 <div>{{ entry.left_text|safe }}</div>
             </div>
+            <!-- Updated Right Text-Block with separate divs for right_text and diff_text -->
             <div class="text-block {{ entry.right_class }}" data-choice="right">
-                <div>{{ entry.right_text|safe }}</div>
+                <div class="right-text">{{ entry.right_text|safe }}</div>
+                <div class="diff-text">{{ entry.diff_text|safe }}</div>
             </div>
         </div>
         {% endfor %}
@@ -221,11 +250,18 @@
                 overlay.classList.remove('active');
             });
 
+            // Handle Reveal Gold/Eval Toggle
             document.getElementById('reveal-toggle').addEventListener('change', (e) => {
                 document.body.classList.toggle('revealed', e.target.checked);
                 updateReveal();
             });
 
+            // Handle Diff Toggle
+            document.getElementById('diff-toggle').addEventListener('change', (e) => {
+                document.body.classList.toggle('diffed', e.target.checked);
+                toggleDiff(e.target.checked);
+            });
+
             // Handle text-block selections
             document.querySelectorAll('.text-block').forEach(block => {
                 block.addEventListener('click', () => selectChoice(block));
@@ -263,7 +299,9 @@
                 }
             });
 
-            updateVoteInfo(datastore);
+            // Ensure diff state is consistent on load
+            const diffToggle = document.getElementById('diff-toggle');
+            toggleDiff(diffToggle.checked);
         }
 
         async function selectChoice(block, save = true) {
@@ -392,6 +430,15 @@
             });
         }
 
+        // Function to toggle diff text
+        function toggleDiff(isDiffed) {
+            if (isDiffed) {
+                document.body.classList.add('diffed');
+            } else {
+                document.body.classList.remove('diffed');
+            }
+        }
+
     </script>
 </body>
 </html>
diff --git a/pdelfin/eval/runeval.py b/pdelfin/eval/runeval.py
index d686674..8bcbb3d 100644
--- a/pdelfin/eval/runeval.py
+++ b/pdelfin/eval/runeval.py
@@ -208,9 +208,11 @@ def process_jsonl_file(jsonl_file, gold_data, comparer):
 
             if data.error is not None:
                 total_errors += 1
+                eval_text = f"[Error processing this page: {data.error}]"
             
             if data.error is None and data.finish_reason != "stop":
                 total_overruns += 1
+                eval_text += f"\n[Error processing this page: overrun {data.finish_reason}]"
 
             if len(gold_text.strip()) < 3 and len(eval_text.strip()) < 3:
                 alignment = 1.0
diff --git a/pyproject.toml b/pyproject.toml
index 23ffcc4..c1b86a4 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -26,7 +26,8 @@ dependencies = [
   "pypdfium2",
   "lingua-language-detector",
   "Pillow",
-  "ftfy"
+  "ftfy",
+  "bleach"
 ]
 license = {file = "LICENSE"}