--- a/src/chat.css	Sun Mar 09 10:55:30 2025 -0600
+++ b/src/chat.css	Sun Mar 09 18:26:49 2025 -0600
@@ -80,6 +80,12 @@
 	max-width: 100%;
 }
 
+div[unread] {
+	font-size: 12px;
+	color: grey;
+	text-align: right;
+}
+
 div[who] {
 	display: flex;
 	justify-content: space-between;

--- a/src/chat.js	Sun Mar 09 10:55:30 2025 -0600
+++ b/src/chat.js	Sun Mar 09 18:26:49 2025 -0600
@@ -227,7 +227,10 @@
 }
 
 function heartbeat() {
-	ajax(`heartbeat.js?last_update=${lastUpdate}`);
+	let url = `heartbeat.js?last_update=${lastUpdate}`;
+	if( currentChatId )
+		url += `&chat=${currentChatId}`;
+	ajax(url);
 }
 
 setInterval( heartbeat, 10000 );
@@ -372,3 +375,19 @@
 	}
 	openModal(dialog);
 }
+
+function readUpTo(userId,userNameHtml,unread) {
+	let div = document.querySelector(`div[user="${userId}"]`);
+	if( div ) {
+		if( unread == div.getAttribute('unread') )
+			return;
+		div.outerHTML = '';
+	} 
+	console.log('readUpTo');
+	let divs = document.querySelectorAll('div[post]');
+	if( unread >= divs.length )
+		return;
+	div = divs[divs.length - unread - 1];
+	let html = `<div user="${userId}" unread="${unread}">read by ${userNameHtml}</div>`;
+	div.insertAdjacentHTML('beforeend',html);
+}

--- a/src/heartbeat.js.luan	Sun Mar 09 10:55:30 2025 -0600
+++ b/src/heartbeat.js.luan	Sun Mar 09 18:26:49 2025 -0600
@@ -1,5 +1,6 @@
 local Luan = require "luan:Luan.luan"
 local error = Luan.error
+local ipairs = Luan.ipairs or error()
 local String = require "luan:String.luan"
 local to_number = String.to_number or error()
 local Parsers = require "luan:Parsers.luan"
@@ -10,11 +11,14 @@
 local Http = require "luan:http/Http.luan"
 local User = require "site:/lib/User.luan"
 local current_user = User.current or error()
+local get_user_by_id = User.get_by_id or error()
 local Shared = require "site:/lib/Shared.luan"
 local compressed = Shared.compressed or error()
 local Online = require "site:/lib/Online.luan"
 local set_online = Online.set or error()
 local get_online = Online.get or error()
+local Chat = require "site:/lib/Chat.luan"
+local get_chat_by_id = Chat.get_by_id or error()
 local Logging = require "luan:logging/Logging.luan"
 local logger = Logging.logger "heartbeat.js"
 
@@ -40,4 +44,16 @@
 	online = <%=json_string(online,compressed)%>;
 	showOnline();
 <%
+	local chat = Http.request.parameters.chat
+	if chat ~= nil then
+		chat = get_chat_by_id(chat) or error()
+		local my_user_id = user.id
+		for _, user_id in ipairs(chat.user_ids) do
+			if user_id == my_user_id then continue end
+			local user = get_user_by_id(user_id)
+%>
+			readUpTo(<%=user_id%>,<%=json_string(user.name_html())%>,<%=chat.unread(user)%>);
+<%
+		end
+	end
 end