diff --git a/apps/ssb/tf-user.js b/apps/ssb/tf-user.js
index 6ed97528..dcdcccb1 100644
--- a/apps/ssb/tf-user.js
+++ b/apps/ssb/tf-user.js
@@ -22,7 +22,8 @@ class TfUserElement extends LitElement {
 		let image = html`<span
 			class="w3-theme-light w3-circle"
 			style="display: inline-block; width: 2em; height: 2em; text-align: center; line-height: 2em"
-		>?</span>`;
+			>?</span
+		>`;
 		let name = this.users?.[this.id]?.name;
 		name =
 			name !== undefined
@@ -31,7 +32,8 @@ class TfUserElement extends LitElement {
 
 		if (this.users[this.id]) {
 			let image_link = this.users[this.id].image;
-			image_link = typeof image_link == 'string' ? image_link : image_link?.link;
+			image_link =
+				typeof image_link == 'string' ? image_link : image_link?.link;
 			if (image_link !== undefined) {
 				image = html`<img
 					class="w3-circle"
@@ -41,8 +43,7 @@ class TfUserElement extends LitElement {
 			}
 		}
 		return html` <div style="display: inline-block; font-weight: bold">
-			${image}
-			${name}
+			${image} ${name}
 		</div>`;
 	}
 }
diff --git a/core/client.js b/core/client.js
index 15ad38b0..792c68e0 100644
--- a/core/client.js
+++ b/core/client.js
@@ -208,7 +208,10 @@ class TfNavigationElement extends LitElement {
 					</div>
 				</div>
 			`;
-		} else if (this.credentials?.session?.name && this.credentials.session.name !== 'guest') {
+		} else if (
+			this.credentials?.session?.name &&
+			this.credentials.session.name !== 'guest'
+		) {
 			return html`
 				<link type="text/css" rel="stylesheet" href="/static/w3.css" />
 				<button
diff --git a/core/core.js b/core/core.js
index f4235192..641de855 100644
--- a/core/core.js
+++ b/core/core.js
@@ -8,116 +8,6 @@ let gStatsTimer = false;
 const k_content_security_policy =
 	'sandbox allow-downloads allow-top-navigation-by-user-activation';
 
-const k_mime_types = {
-	css: 'text/css',
-	html: 'text/html',
-	js: 'text/javascript',
-	json: 'text/json',
-	map: 'application/json',
-	svg: 'image/svg+xml',
-};
-
-const k_magic_bytes = [
-	{bytes: [0xff, 0xd8, 0xff, 0xdb], type: 'image/jpeg'},
-	{
-		bytes: [
-			0xff, 0xd8, 0xff, 0xe0, 0x00, 0x10, 0x4a, 0x46, 0x49, 0x46, 0x00, 0x01,
-		],
-		type: 'image/jpeg',
-	},
-	{bytes: [0xff, 0xd8, 0xff, 0xee], type: 'image/jpeg'},
-	{
-		bytes: [
-			0xff,
-			0xd8,
-			0xff,
-			0xe1,
-			null,
-			null,
-			0x45,
-			0x78,
-			0x69,
-			0x66,
-			0x00,
-			0x00,
-		],
-		type: 'image/jpeg',
-	},
-	{bytes: [0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a], type: 'image/png'},
-	{bytes: [0x47, 0x49, 0x46, 0x38, 0x37, 0x61], type: 'image/gif'},
-	{bytes: [0x47, 0x49, 0x46, 0x38, 0x39, 0x61], type: 'image/gif'},
-	{
-		bytes: [
-			0x52,
-			0x49,
-			0x46,
-			0x46,
-			null,
-			null,
-			null,
-			null,
-			0x57,
-			0x45,
-			0x42,
-			0x50,
-		],
-		type: 'image/webp',
-	},
-	{bytes: [0x3c, 0x73, 0x76, 0x67], type: 'image/svg+xml'},
-	{
-		bytes: [
-			null,
-			null,
-			null,
-			null,
-			0x66,
-			0x74,
-			0x79,
-			0x70,
-			0x6d,
-			0x70,
-			0x34,
-			0x32,
-		],
-		type: 'audio/mpeg',
-	},
-	{
-		bytes: [
-			null,
-			null,
-			null,
-			null,
-			0x66,
-			0x74,
-			0x79,
-			0x70,
-			0x69,
-			0x73,
-			0x6f,
-			0x6d,
-		],
-		type: 'video/mp4',
-	},
-	{
-		bytes: [
-			null,
-			null,
-			null,
-			null,
-			0x66,
-			0x74,
-			0x79,
-			0x70,
-			0x6d,
-			0x70,
-			0x34,
-			0x32,
-		],
-		type: 'video/mp4',
-	},
-	{bytes: [0x4d, 0x54, 0x68, 0x64], type: 'audio/midi'},
-];
-
 let k_static_files = [
 	{uri: '/', path: 'index.html', type: 'text/html; charset=UTF-8'},
 ];
@@ -941,29 +831,6 @@ function startsWithBytes(data, bytes) {
 	}
 }
 
-/**
- * TODOC
- * @param {*} path
- * @returns
- */
-function guessTypeFromName(path) {
-	let extension = path.split('.').pop();
-	return k_mime_types[extension];
-}
-
-/**
- * TODOC
- * @param {*} data
- * @returns
- */
-function guessTypeFromMagicBytes(data) {
-	for (let magic of k_magic_bytes) {
-		if (startsWithBytes(data, magic.bytes)) {
-			return magic.type;
-		}
-	}
-}
-
 /**
  * TODOC
  * @param {*} response
@@ -979,7 +846,9 @@ function sendData(response, data, type, headers, status_code) {
 			Object.assign(
 				{
 					'Content-Type':
-						type || guessTypeFromMagicBytes(data) || 'application/binary',
+						type ||
+						httpd.mime_type_from_magic_bytes(data) ||
+						'application/binary',
 					'Content-Length': data.byteLength,
 				},
 				headers || {}
@@ -1348,7 +1217,9 @@ async function blobHandler(request, response, blobId, uri) {
 					'Content-Security-Policy': k_content_security_policy,
 				};
 				data = await getBlobOrContent(id);
-				let type = guessTypeFromName(uri) || guessTypeFromMagicBytes(data);
+				let type =
+					httpd.mime_type_from_extension(uri) ||
+					httpd.mime_type_from_magic_bytes(data);
 				sendData(response, data, type, headers);
 			}
 		} else {
diff --git a/src/httpd.js.c b/src/httpd.js.c
index 38798e9b..49cb9cea 100644
--- a/src/httpd.js.c
+++ b/src/httpd.js.c
@@ -498,6 +498,151 @@ static JSValue _httpd_auth_query(JSContext* context, JSValueConst this_val, int
 	return result;
 }
 
+typedef struct _magic_bytes_t
+{
+	const char* type;
+	uint8_t bytes[12];
+	uint8_t ignore[12];
+} magic_bytes_t;
+
+static bool _magic_bytes_match(const magic_bytes_t* magic, const uint8_t* actual, size_t size)
+{
+	if (size < sizeof(magic->bytes))
+	{
+		return false;
+	}
+
+	int length = (int)tf_min(sizeof(magic->bytes), size);
+	for (int i = 0; i < length; i++)
+	{
+		if ((magic->bytes[i] & ~magic->ignore[i]) != (actual[i] & ~magic->ignore[i]))
+		{
+			return false;
+		}
+	}
+	return true;
+}
+
+static JSValue _httpd_mime_type_from_magic_bytes(JSContext* context, JSValueConst this_val, int argc, JSValueConst* argv)
+{
+	JSValue result = JS_UNDEFINED;
+	size_t size = 0;
+	uint8_t* bytes = tf_util_try_get_array_buffer(context, &size, argv[0]);
+	if (bytes)
+	{
+
+		const magic_bytes_t k_magic_bytes[] = {
+			{
+				.type = "image/jpeg",
+				.bytes = { 0xff, 0xd8, 0xff, 0xdb },
+			},
+			{
+				.type = "image/jpeg",
+				.bytes = { 0xff, 0xd8, 0xff, 0xe0, 0x00, 0x10, 0x4a, 0x46, 0x49, 0x46, 0x00, 0x01 },
+			},
+			{
+				.type = "image/jpeg",
+				.bytes = { 0xff, 0xd8, 0xff, 0xee },
+			},
+			{
+				.type = "image/jpeg",
+				.bytes = { 0xff, 0xd8, 0xff, 0xe1, 0x00, 0x00, 0x45, 0x78, 0x69, 0x66, 0x00, 0x00 },
+				.ignore = { 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
+			},
+			{
+				.type = "image/png",
+				.bytes = { 0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a },
+			},
+			{
+				.type = "image/gif",
+				.bytes = { 0x47, 0x49, 0x46, 0x38, 0x37, 0x61 },
+			},
+			{
+				.type = "image/gif",
+				.bytes = { 0x47, 0x49, 0x46, 0x38, 0x39, 0x61 },
+			},
+			{
+				.type = "image/webp",
+				.bytes = { 0x52, 0x49, 0x46, 0x46, 0x00, 0x00, 0x00, 0x00, 0x57, 0x45, 0x42, 0x50 },
+				.ignore = { 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff, 0x00, 0x00, 0x00, 0x00 },
+			},
+			{
+				.type = "image/svg+xml",
+				.bytes = { 0x3c, 0x73, 0x76, 0x67 },
+			},
+			{
+				.type = "audio/mpeg",
+				.bytes = { 0x00, 0x00, 0x00, 0x00, 0x66, 0x74, 0x79, 0x70, 0x6d, 0x70, 0x34, 0x32 },
+				.ignore = { 0xff, 0xff, 0xff, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
+			},
+			{
+				.type = "video/mp4",
+				.bytes = { 0x00, 0x00, 0x00, 0x00, 0x66, 0x74, 0x79, 0x70, 0x69, 0x73, 0x6f, 0x6d },
+				.ignore = { 0xff, 0xff, 0xff, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
+			},
+			{
+				.type = "video/mp4",
+				.bytes = { 0x00, 0x00, 0x00, 0x00, 0x66, 0x74, 0x79, 0x70, 0x6d, 0x70, 0x34, 0x32 },
+				.ignore = { 0xff, 0xff, 0xff, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
+			},
+			{
+				.type = "audio/midi",
+				.bytes = { 0x4d, 0x54, 0x68, 0x64 },
+			},
+		};
+
+		for (int i = 0; i < tf_countof(k_magic_bytes); i++)
+		{
+			if (_magic_bytes_match(&k_magic_bytes[i], bytes, size))
+			{
+				result = JS_NewString(context, k_magic_bytes[i].type);
+				break;
+			}
+		}
+	}
+	return result;
+}
+
+static const char* _ext_to_content_type(const char* ext, bool use_fallback)
+{
+	if (ext)
+	{
+		typedef struct _ext_type_t
+		{
+			const char* ext;
+			const char* type;
+		} ext_type_t;
+
+		const ext_type_t k_types[] = {
+			{ .ext = ".html", .type = "text/html; charset=UTF-8" },
+			{ .ext = ".js", .type = "text/javascript; charset=UTF-8" },
+			{ .ext = ".mjs", .type = "text/javascript; charset=UTF-8" },
+			{ .ext = ".css", .type = "text/css; charset=UTF-8" },
+			{ .ext = ".png", .type = "image/png" },
+			{ .ext = ".json", .type = "application/json" },
+			{ .ext = ".map", .type = "application/json" },
+			{ .ext = ".svg", .type = "image/svg+xml" },
+		};
+
+		for (int i = 0; i < tf_countof(k_types); i++)
+		{
+			if (strcmp(ext, k_types[i].ext) == 0)
+			{
+				return k_types[i].type;
+			}
+		}
+	}
+	return use_fallback ? "application/binary" : NULL;
+}
+
+static JSValue _httpd_mime_type_from_extension(JSContext* context, JSValueConst this_val, int argc, JSValueConst* argv)
+{
+	const char* name = JS_ToCString(context, argv[0]);
+	const char* type = _ext_to_content_type(strrchr(name, '.'), false);
+	JS_FreeCString(context, name);
+	return type ? JS_NewString(context, type) : JS_UNDEFINED;
+}
+
 static void _httpd_finalizer(JSRuntime* runtime, JSValue value)
 {
 	tf_http_t* http = JS_GetOpaque(value, _httpd_class_id);
@@ -627,30 +772,6 @@ typedef struct _http_file_t
 	char etag[512];
 } http_file_t;
 
-static const char* _ext_to_content_type(const char* ext)
-{
-	if (ext)
-	{
-		if (strcmp(ext, ".html") == 0)
-		{
-			return "text/html; charset=UTF-8";
-		}
-		else if (strcmp(ext, ".js") == 0 || strcmp(ext, ".mjs") == 0)
-		{
-			return "text/javascript; charset=UTF-8";
-		}
-		else if (strcmp(ext, ".css") == 0)
-		{
-			return "text/css; charset=UTF-8";
-		}
-		else if (strcmp(ext, ".png") == 0)
-		{
-			return "image/png";
-		}
-	}
-	return "application/binary";
-}
-
 static void _httpd_endpoint_static_read(tf_task_t* task, const char* path, int result, const void* data, void* user_data)
 {
 	http_file_t* file = user_data;
@@ -659,7 +780,7 @@ static void _httpd_endpoint_static_read(tf_task_t* task, const char* path, int r
 	{
 		if (strcmp(path, "core/tfrpc.js") == 0)
 		{
-			const char* content_type = _ext_to_content_type(strrchr(path, '.'));
+			const char* content_type = _ext_to_content_type(strrchr(path, '.'), true);
 			const char* headers[] = {
 				"Content-Type",
 				content_type,
@@ -672,7 +793,7 @@ static void _httpd_endpoint_static_read(tf_task_t* task, const char* path, int r
 		}
 		else
 		{
-			const char* content_type = _ext_to_content_type(strrchr(path, '.'));
+			const char* content_type = _ext_to_content_type(strrchr(path, '.'), true);
 			const char* headers[] = {
 				"Content-Type",
 				content_type,
@@ -1519,6 +1640,8 @@ void tf_httpd_register(JSContext* context)
 	JS_SetPropertyStr(context, httpd, "start", JS_NewCFunction(context, _httpd_endpoint_start, "start", 2));
 	JS_SetPropertyStr(context, httpd, "set_http_redirect", JS_NewCFunction(context, _httpd_set_http_redirect, "set_http_redirect", 1));
 	JS_SetPropertyStr(context, httpd, "auth_query", JS_NewCFunction(context, _httpd_auth_query, "auth_query", 1));
+	JS_SetPropertyStr(context, httpd, "mime_type_from_magic_bytes", JS_NewCFunction(context, _httpd_mime_type_from_magic_bytes, "mime_type_from_magic_bytes", 1));
+	JS_SetPropertyStr(context, httpd, "mime_type_from_extension", JS_NewCFunction(context, _httpd_mime_type_from_extension, "mime_type_from_extension", 1));
 	JS_SetPropertyStr(context, global, "httpd", httpd);
 	JS_FreeValue(context, global);
 }