diff --git a/poptimal.js b/poptimal.js
index 7a0e334..ce920bf 100644
--- a/poptimal.js
+++ b/poptimal.js
@@ -179,7 +179,53 @@ function poptimal_svg(params) {
 }
 
 
-async function post_image(image, alt_text, cf) {
+async function send_replies(argv, cf) {
+
+	const mentionsjson = await promises.readFile(cf.mentions);
+  	const oldids = JSON.parse(mentionsjson).map((m) => m.id);
+
+	const params = new URLSearchParams();
+
+	params.append("types", ["mention"]) // this isn't working
+	                                    // so filter it explicitly
+	const notifications_url = `${cf.base_url}/api/v1/notifications?${params}`;
+	const headers = {
+		'Authorization': `Bearer ${cf.access_token}`,
+	};
+	const resp = await fetch(notifications_url, {
+		method: 'GET',
+		headers: headers,
+	});
+
+	const bodyjson = await resp.text();
+	const response = JSON.parse(bodyjson);
+	const mentions = response.filter((s) => s.type === "mention").map((s) => {
+    		const account = s.account;
+    		const status = s.status;
+    		return {
+        		id: s.id,
+        		created: s.created_at,
+        		status_id: status.id,
+        		account: account.acct,
+        		url: status.url
+    		};
+    	});
+	const newmentions = mentions.filter((m) => !oldids.includes(m.id));
+	for (const mention of newmentions) {
+    	    console.log(`new mention ${mention.id}`);
+    	    const reply = {
+        	    id: mention.status_id,
+        	    account: `@${mention.account}`
+    	    };
+    	    
+    	    post(argv, cf, reply);
+	}
+        if( !argv.n ) {
+		await promises.writeFile(cf.mentions, JSON.stringify(mentions, null, 4));
+        }
+}
+
+async function post_image(image, alt_text, cf, reply) {
 	const status_url = `${cf.base_url}/api/v1/statuses`;
 	const media_url = `${cf.base_url}/api/v1/media`;
 	const headers = {
@@ -199,36 +245,45 @@ async function post_image(image, alt_text, cf) {
 	const bodyjson = await resp.text();
 	const response = JSON.parse(bodyjson);
 	const media_id = response["id"];
-
+	const status_body = { media_ids: [ media_id ] };
+	if( reply ) {
+    	    status_body["in_reply_to_id"] = reply.id;
+    	    status_body["status"] = reply.account;
+	}
 	headers['Accept'] = 'application/json';
 	headers['Content-Type'] = 'application/json';
 	const resp2 = await fetch(status_url, {
 		method: 'POST',
 		headers: headers,
-		body: JSON.stringify({ media_ids: [ media_id ] })
+		body: JSON.stringify(status_body)
 	});
 	const bodyjson2 = await resp2.text();
 
 }
 
 
-async function main() {
-	const argv = yargs(hideBin(process.argv))
-		.usage("Usage: -s SIZE [-o output] -c config.json [-p params.json]")
-		.default('s', 1200)
-		.default('c', 'config.json').argv;
 
-	const cfjson = await promises.readFile(argv.c);
-  	const cf = JSON.parse(cfjson);
+
+function make_unique_filename(reply_to) {
 
         const ts = String(Date.now());
+        if( reply_to ) {
+            return `${ts}-${reply_to.id}`;
+        } else {
+            return ts;
+        }
+}
 
-  	const fn = (argv.o || ts) + '.png';
-	const jsfn = (argv.o || ts) + '.json';
+
+async function post(argv, cf, reply_to) {
+	const filebase = make_unique_filename(reply_to);
+ 	const fn = (argv.o || filebase) + '.png';
+	const jsfn = (argv.o || filebase) + '.json';
 
   	const imgfile = cf['working_dir'] + '/' + fn;
 	const paramsfile = cf['working_dir'] + '/' + jsfn;
 
+	console.log(`Generating ${imgfile}`);
 	const params = await load_or_random_params(argv.p);
 	const colourf = params.palette === 'grayscale' ? cf['grayscale'] : cf['colour'];
 
@@ -238,19 +293,18 @@ async function main() {
 
 	const svg = poptimal_svg(params);
 	const opts = {
-    	background: 'rgba(255, 255, 255, 1.0)',
-    	fitTo: {
-      		mode: 'width',
-      		value: argv.s,
-    	},
-    };
+    		background: 'rgba(255, 255, 255, 1.0)',
+    		fitTo: {
+      			mode: 'width',
+      			value: argv.s,
+    		},
+    	};
 
   	const resvg = new Resvg(svg, opts);
  	const pngData = resvg.render();
   	const pngBuffer = pngData.asPng();
 
   	await promises.writeFile(imgfile, pngBuffer);
-
   	// generate the alt_text last to check the image file histogram
   	// so we don't include obscured colours
   	const hist = await get_histogram(imgfile);
@@ -258,12 +312,34 @@ async function main() {
 	params.alt_text = alt_text;
 	await save_params(paramsfile, params);
 	console.log(alt_text);
-	console.log(imgfile);
-  	if( cf['base_url'] ) {
-  		await post_image(imgfile, alt_text, cf);
+  	if( cf['base_url'] && !argv.n ) {
+  		await post_image(imgfile, alt_text, cf, reply_to);
   	}
 }
 
 
+async function main() {
+	const argv = yargs(hideBin(process.argv))
+		.usage("Usage: -s SIZE [-o output] [-r] [-n] -c config.json [-p params.json]")
+		.default('s', 1200)
+		.default('c', 'config.json').argv;
+
+	const cfjson = await promises.readFile(argv.c);
+  	const cf = JSON.parse(cfjson);
+
+
+        if( argv.r ) {
+                if( !cf.base_url ) {
+                    	console.log("Can't check mentions without base_url");
+                } else {
+       	     		send_replies(argv, cf);
+                }
+        } else {
+        	post(argv, cf);
+        }
+
+}
+
+
 
 main();