diff --git a/extensions/perplexity_colors/script.py b/extensions/perplexity_colors/script.py
new file mode 100644
index 00000000..84b62a30
--- /dev/null
+++ b/extensions/perplexity_colors/script.py
@@ -0,0 +1,215 @@
+import gradio
+import torch
+from transformers import LogitsProcessor
+import numpy as np
+
+from modules import shared
+
+params = {
+    'color_by_perplexity': False,
+    'color_by_probability': False,
+    'ppl_scale': 15.0, # No slider for this right now, because I don't think it really needs to be changed. Very large perplexity scores don't show up often.
+    #'probability_dropdown': False
+}
+
+class PerplexityLogits(LogitsProcessor):
+    def __init__(self, verbose=False):
+        self.generated_token_ids = []
+        self.selected_probs = []
+        self.top_token_ids_list = []
+        self.top_probs_list = []
+        self.perplexities_list = []
+        self.last_probs = None
+        self.verbose = verbose
+
+    def __call__(self, input_ids, scores):
+        probs = torch.softmax(scores, dim=-1, dtype=torch.float)
+        log_probs = torch.nan_to_num(torch.log(probs))
+        entropy = -torch.sum(probs*log_probs)
+        entropy = entropy.cpu().numpy()
+        perplexity = round(float(np.exp(entropy)), 4)
+        self.perplexities_list.append(perplexity)
+        last_token_id = int(input_ids[0][-1].cpu().numpy().item())
+        # Store the generated tokens (not sure why this isn't accessible in the output endpoint!)
+        self.generated_token_ids.append(last_token_id)
+        # Get last probability, and add to the list if it wasn't there
+        if len(self.selected_probs) > 0:
+            # Is the selected token in the top tokens?
+            if self.verbose:
+                print(shared.tokenizer.decode(last_token_id))
+                print([shared.tokenizer.decode(token_id) for token_id in self.top_token_ids_list[-1]])
+                print(self.top_probs_list[-1])
+            if last_token_id in self.top_token_ids_list[-1]:
+                idx = self.top_token_ids_list[-1].index(last_token_id)
+                self.selected_probs.append(self.top_probs_list[-1][idx])
+            else:
+                self.top_token_ids_list[-1].append(last_token_id)
+                last_prob = round(float(self.last_probs[last_token_id]), 4)
+                self.top_probs_list[-1].append(last_prob)
+                self.selected_probs.append(last_prob)
+        else:
+            self.selected_probs.append(1.0) # Placeholder for the last token of the prompt
+
+        if self.verbose:
+            pplbar = "-"
+            if not np.isnan(perplexity):
+                pplbar = "*"*round(perplexity)
+            print(f"{last_token}\t{perplexity:.2f}\t{pplbar}")
+
+        # Get top 5 probabilities
+        top_tokens_and_probs = torch.topk(probs, 5)
+        top_probs = top_tokens_and_probs.values.cpu().numpy().astype(float).tolist()
+        top_token_ids = top_tokens_and_probs.indices.cpu().numpy().astype(int).tolist()
+
+        self.top_token_ids_list.append(top_token_ids)
+        self.top_probs_list.append(top_probs)
+        
+        probs = probs.cpu().numpy().flatten()
+        self.last_probs = probs # Need to keep this as a reference for top probs
+
+        # Doesn't actually modify the logits!
+        return scores
+
+# Stores the perplexity and top probabilities
+ppl_logits_processor = None
+
+def logits_processor_modifier(logits_processor_list, input_ids):
+    global ppl_logits_processor
+    ppl_logits_processor = PerplexityLogits()
+    logits_processor_list.append(ppl_logits_processor)
+
+def output_modifier(text):
+    global ppl_logits_processor
+
+    # TODO: It's probably more efficient to do this above rather than modifying all these lists
+    # Remove last element of perplexities_list, top_token_ids_list, top_tokens_list, top_probs_list since everything is off by one because this extension runs before generation
+    perplexities = ppl_logits_processor.perplexities_list[:-1]
+    top_token_ids_list = ppl_logits_processor.top_token_ids_list[:-1]
+    top_tokens_list = [[shared.tokenizer.decode(token_id) for token_id in top_token_ids] for top_token_ids in top_token_ids_list]
+    top_probs_list = ppl_logits_processor.top_probs_list[:-1]
+    # Remove first element of generated_token_ids, generated_tokens, selected_probs because they are for the last token of the prompt
+    gen_token_ids = ppl_logits_processor.generated_token_ids[1:]
+    gen_tokens = [shared.tokenizer.decode(token_id) for token_id in gen_token_ids]
+    sel_probs = ppl_logits_processor.selected_probs[1:]
+
+    end_part = '</span>' # Helps with finding the index after replacing part of the text.
+    in_code = False # Since the <span> tags mess up code blocks, avoid coloring while inside a code block, based on finding tokens with '`' in them
+
+    if params['color_by_probability'] and params['color_by_perplexity']:
+        i = 0
+        for token, prob, ppl, top_tokens, top_probs in zip(gen_tokens, sel_probs, perplexities, top_tokens_list, top_probs_list):
+            if '`' in token:
+                in_code = not in_code
+                continue
+            if in_code:
+                continue
+            color = probability_perplexity_color_scale(prob, ppl)
+            if token in text[i:]:
+                text = text[:i] + text[i:].replace(token, add_color_html(token, color), 1)
+                i += text[i:].find(end_part) + len(end_part)
+    elif params['color_by_perplexity']:
+        i = 0
+        for token, ppl, top_tokens, top_probs in zip(gen_tokens, perplexities, top_tokens_list, top_probs_list):
+            if '`' in token:
+                in_code = not in_code
+                continue
+            if in_code:
+                continue
+            color = perplexity_color_scale(ppl)
+            if token in text[i:]:
+                text = text[:i] + text[i:].replace(token, add_color_html(token, color), 1)
+                i += text[i:].find(end_part) + len(end_part)
+    elif params['color_by_probability']:
+        i = 0
+        for token, prob, top_tokens, top_probs in zip(gen_tokens, sel_probs, top_tokens_list, top_probs_list):
+            if '`' in token:
+                in_code = not in_code
+                continue
+            if in_code:
+                continue
+            color = probability_color_scale(prob)
+            if token in text[i:]:
+                text = text[:i] + text[i:].replace(token, add_color_html(token, color), 1)
+                i += text[i:].find(end_part) + len(end_part)
+
+    print('Average perplexity:', round(np.mean(perplexities), 4))
+    return text
+
+# Green-yellow-red color scale
+def probability_color_scale(prob):
+    rv = 0
+    gv = 0
+    if prob <= 0.5:
+        rv = 'ff'
+        gv = hex(int(255*prob*2))[2:]
+        if len(gv) < 2:
+            gv = '0'*(2 - len(gv)) + gv
+    else:
+        rv = hex(int(255 - 255*(prob - 0.5)*2))[2:]
+        gv = 'ff'
+        if len(rv) < 2:
+            rv = '0'*(2 - len(rv)) + rv
+    return rv + gv + '00'
+
+# Red component only, white for 0 perplexity (sorry if you're not in dark mode)
+def perplexity_color_scale(ppl):
+    value = hex(max(int(255.0 - params['ppl_scale']*(float(ppl)-1.0)), 0))[2:]
+    if len(value) < 2:
+        value = '0'*(2 - len(value)) + value
+    return 'ff' + value + value
+
+# Green-yellow-red for probability and blue component for perplexity
+def probability_perplexity_color_scale(prob, ppl):
+    rv = 0
+    gv = 0
+    bv = hex(min(max(int(params['ppl_scale']*(float(ppl)-1.0)), 0), 255))[2:]
+    if len(bv) < 2:
+            bv = '0'*(2 - len(bv)) + bv
+    if prob <= 0.5:
+        rv = 'ff'
+        gv = hex(int(255*prob*2))[2:]
+        if len(gv) < 2:
+            gv = '0'*(2 - len(gv)) + gv
+    else:
+        rv = hex(int(255 - 255*(prob - 0.5)*2))[2:]
+        gv = 'ff'
+        if len(rv) < 2:
+            rv = '0'*(2 - len(rv)) + rv
+    return rv + gv + bv
+
+def add_color_html(token, color):
+    return f'<span style="color: #{color}">{token}</span>'
+
+"""
+# This is still very broken at the moment, needs CSS too but I'm not very good at CSS (and neither is GPT-4 apparently) so I still need to figure that out.
+def add_dropdown_html(token, color, top_tokens, top_probs):
+    html = f'<span class="hoverable" style="color: #{color}">{token}<div class="dropdown"><table class="dropdown-content">'
+    for token, prob in zip(top_tokens, top_probs):
+        # TODO: Background color? Bold for selected token?
+        # Bigger issue: Why is there a newline after the first token, and the dropdown fails there?
+        # The HTML ends up like <p><span>word</span></p><div>...</div>,
+        # even though for all other tokens it shows up correctly.
+        row_color = probability_color_scale(prob)
+        html += f'<tr><td style="color: #{row_color}">{token}</td><td style="color: #{row_color}">{prob}</td></tr>'
+    html += '</table></div></span>'
+    return html
+"""
+
+def ui():
+    color_by_ppl_check = gradio.Checkbox(value=False, label="Color by perplexity", info="Higher perplexity is more red. If also showing probability, higher perplexity has more blue component.")
+    def update_color_by_ppl_check(x):
+        params.update({'color_by_perplexity': x})
+    color_by_ppl_check.change(update_color_by_ppl_check, color_by_ppl_check, None)
+
+    color_by_prob_check = gradio.Checkbox(value=False, label="Color by probability", info="Green-yellow-red linear scale, with 100% green, 50% yellow, 0% red.")
+    def update_color_by_prob_check(x):
+        params.update({'color_by_probability': x})
+    color_by_prob_check.change(update_color_by_prob_check, color_by_prob_check, None)
+
+    # Doesn't work yet...
+    """
+    prob_dropdown_check = gradio.Checkbox(value=False, label="Probability dropdown")
+    def update_prob_dropdown_check(x):
+        params.update({'probability_dropdown': x})
+    prob_dropdown_check.change(update_prob_dropdown_check, prob_dropdown_check, None)
+    """