diff --git a/public/scripts/network.js b/public/scripts/network.js
index ca0a41a..07333a3 100644
--- a/public/scripts/network.js
+++ b/public/scripts/network.js
@@ -5,7 +5,6 @@ if (!crypto.subtle && localStorage.getItem('unsecure_warning') !== 'received') {
     alert("PairDrops functionality to compare received with requested files works in secure contexts only (https or localhost).")
     localStorage.setItem('unsecure_warning', 'received')
 }
-
 class ServerConnection {
 
     constructor() {
@@ -697,7 +696,20 @@ class PeersManager {
     }
 
     _onFilesSelected(message) {
-        this.peers[message.to].requestFileTransfer(message.files);
+        const files = this._addTypeIfMissing(message.files);
+        this.peers[message.to].requestFileTransfer(files);
+    }
+
+    _addTypeIfMissing(files) {
+        let filesWithType = [], file;
+        for (let i=0; i<files.length; i++) {
+            // when filename is empty guess via suffix
+            file = files[i].type
+                ? files[i]
+                : new File([files[i]], files[i].name, {type: mime.getMimeByFilename(files[i].name)});
+            filesWithType.push(file)
+        }
+        return filesWithType;
     }
 
     _onSendText(message) {
diff --git a/public/scripts/ui.js b/public/scripts/ui.js
index 83f5d39..4562b4d 100644
--- a/public/scripts/ui.js
+++ b/public/scripts/ui.js
@@ -639,7 +639,7 @@ class ReceiveRequestDialog extends ReceiveDialog {
         if (request.thumbnailDataUrl) {
             let element = document.createElement('img');
             element.src = request.thumbnailDataUrl;
-            element.classList = 'element-preview'
+            element.classList.add('element-preview');
 
             this.$previewBox.style.display = 'block';
             this.$previewBox.appendChild(element)
diff --git a/public/scripts/util.js b/public/scripts/util.js
index 9cd837c..5c8831c 100644
--- a/public/scripts/util.js
+++ b/public/scripts/util.js
@@ -74,3 +74,309 @@ const zipper = (() => {
     };
 
 })();
+
+const mime = (() => {
+
+    return {
+        getMimeByFilename(filename) {
+            try {
+                const arr = filename.split('.');
+                const suffix = arr[arr.length - 1];
+                return {
+                    "cpl": "application/cpl+xml",
+                    "gpx": "application/gpx+xml",
+                    "gz": "application/gzip",
+                    "jar": "application/java-archive",
+                    "war": "application/java-archive",
+                    "ear": "application/java-archive",
+                    "class": "application/java-vm",
+                    "js": "application/javascript",
+                    "mjs": "application/javascript",
+                    "json": "application/json",
+                    "map": "application/json",
+                    "webmanifest": "application/manifest+json",
+                    "doc": "application/msword",
+                    "dot": "application/msword",
+                    "wiz": "application/msword",
+                    "bin": "application/octet-stream",
+                    "dms": "application/octet-stream",
+                    "lrf": "application/octet-stream",
+                    "mar": "application/octet-stream",
+                    "so": "application/octet-stream",
+                    "dist": "application/octet-stream",
+                    "distz": "application/octet-stream",
+                    "pkg": "application/octet-stream",
+                    "bpk": "application/octet-stream",
+                    "dump": "application/octet-stream",
+                    "elc": "application/octet-stream",
+                    "deploy": "application/octet-stream",
+                    "img": "application/octet-stream",
+                    "msp": "application/octet-stream",
+                    "msm": "application/octet-stream",
+                    "buffer": "application/octet-stream",
+                    "oda": "application/oda",
+                    "oxps": "application/oxps",
+                    "pdf": "application/pdf",
+                    "asc": "application/pgp-signature",
+                    "sig": "application/pgp-signature",
+                    "prf": "application/pics-rules",
+                    "p7c": "application/pkcs7-mime",
+                    "cer": "application/pkix-cert",
+                    "ai": "application/postscript",
+                    "eps": "application/postscript",
+                    "ps": "application/postscript",
+                    "apk": "application/vnd.android.package-archive",
+                    "m3u8": "application/vnd.apple.mpegurl",
+                    "pkpass": "application/vnd.apple.pkpass",
+                    "kml": "application/vnd.google-earth.kml+xml",
+                    "kmz": "application/vnd.google-earth.kmz",
+                    "cab": "application/vnd.ms-cab-compressed",
+                    "xls": "application/vnd.ms-excel",
+                    "xlm": "application/vnd.ms-excel",
+                    "xla": "application/vnd.ms-excel",
+                    "xlc": "application/vnd.ms-excel",
+                    "xlt": "application/vnd.ms-excel",
+                    "xlw": "application/vnd.ms-excel",
+                    "msg": "application/vnd.ms-outlook",
+                    "ppt": "application/vnd.ms-powerpoint",
+                    "pot": "application/vnd.ms-powerpoint",
+                    "ppa": "application/vnd.ms-powerpoint",
+                    "pps": "application/vnd.ms-powerpoint",
+                    "pwz": "application/vnd.ms-powerpoint",
+                    "mpp": "application/vnd.ms-project",
+                    "mpt": "application/vnd.ms-project",
+                    "xps": "application/vnd.ms-xpsdocument",
+                    "odb": "application/vnd.oasis.opendocument.database",
+                    "ods": "application/vnd.oasis.opendocument.spreadsheet",
+                    "odt": "application/vnd.oasis.opendocument.text",
+                    "osm": "application/vnd.openstreetmap.data+xml",
+                    "pptx": "application/vnd.openxmlformats-officedocument.presentationml.presentation",
+                    "xlsx": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
+                    "docx": "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
+                    "pcap": "application/vnd.tcpdump.pcap",
+                    "cap": "application/vnd.tcpdump.pcap",
+                    "dmp": "application/vnd.tcpdump.pcap",
+                    "wpd": "application/vnd.wordperfect",
+                    "wasm": "application/wasm",
+                    "7z": "application/x-7z-compressed",
+                    "dmg": "application/x-apple-diskimage",
+                    "bcpio": "application/x-bcpio",
+                    "torrent": "application/x-bittorrent",
+                    "cbr": "application/x-cbr",
+                    "cba": "application/x-cbr",
+                    "cbt": "application/x-cbr",
+                    "cbz": "application/x-cbr",
+                    "cb7": "application/x-cbr",
+                    "vcd": "application/x-cdlink",
+                    "crx": "application/x-chrome-extension",
+                    "cpio": "application/x-cpio",
+                    "csh": "application/x-csh",
+                    "deb": "application/x-debian-package",
+                    "udeb": "application/x-debian-package",
+                    "dvi": "application/x-dvi",
+                    "arc": "application/x-freearc",
+                    "gtar": "application/x-gtar",
+                    "hdf": "application/x-hdf",
+                    "h5": "application/x-hdf5",
+                    "php": "application/x-httpd-php",
+                    "iso": "application/x-iso9660-image",
+                    "key": "application/x-iwork-keynote-sffkey",
+                    "numbers": "application/x-iwork-numbers-sffnumbers",
+                    "pages": "application/x-iwork-pages-sffpages",
+                    "latex": "application/x-latex",
+                    "run": "application/x-makeself",
+                    "mif": "application/x-mif",
+                    "lnk": "application/x-ms-shortcut",
+                    "mdb": "application/x-msaccess",
+                    "exe": "application/x-msdownload",
+                    "dll": "application/x-msdownload",
+                    "com": "application/x-msdownload",
+                    "bat": "application/x-msdownload",
+                    "msi": "application/x-msdownload",
+                    "pub": "application/x-mspublisher",
+                    "cdf": "application/x-netcdf",
+                    "nc": "application/x-netcdf",
+                    "pl": "application/x-perl",
+                    "pm": "application/x-perl",
+                    "prc": "application/x-pilot",
+                    "pdb": "application/x-pilot",
+                    "p12": "application/x-pkcs12",
+                    "pfx": "application/x-pkcs12",
+                    "ram": "application/x-pn-realaudio",
+                    "pyc": "application/x-python-code",
+                    "pyo": "application/x-python-code",
+                    "rar": "application/x-rar-compressed",
+                    "rpm": "application/x-redhat-package-manager",
+                    "sh": "application/x-sh",
+                    "shar": "application/x-shar",
+                    "swf": "application/x-shockwave-flash",
+                    "sql": "application/x-sql",
+                    "srt": "application/x-subrip",
+                    "sv4cpio": "application/x-sv4cpio",
+                    "sv4crc": "application/x-sv4crc",
+                    "gam": "application/x-tads",
+                    "tar": "application/x-tar",
+                    "tcl": "application/x-tcl",
+                    "tex": "application/x-tex",
+                    "roff": "application/x-troff",
+                    "t": "application/x-troff",
+                    "tr": "application/x-troff",
+                    "man": "application/x-troff-man",
+                    "me": "application/x-troff-me",
+                    "ms": "application/x-troff-ms",
+                    "ustar": "application/x-ustar",
+                    "src": "application/x-wais-source",
+                    "xpi": "application/x-xpinstall",
+                    "xhtml": "application/xhtml+xml",
+                    "xht": "application/xhtml+xml",
+                    "xsl": "application/xml",
+                    "rdf": "application/xml",
+                    "wsdl": "application/xml",
+                    "xpdl": "application/xml",
+                    "zip": "application/zip",
+                    "3gp": "audio/3gp",
+                    "3gpp": "audio/3gpp",
+                    "3g2": "audio/3gpp2",
+                    "3gpp2": "audio/3gpp2",
+                    "aac": "audio/aac",
+                    "adts": "audio/aac",
+                    "loas": "audio/aac",
+                    "ass": "audio/aac",
+                    "au": "audio/basic",
+                    "snd": "audio/basic",
+                    "mid": "audio/midi",
+                    "midi": "audio/midi",
+                    "kar": "audio/midi",
+                    "rmi": "audio/midi",
+                    "mpga": "audio/mpeg",
+                    "mp2": "audio/mpeg",
+                    "mp2a": "audio/mpeg",
+                    "mp3": "audio/mpeg",
+                    "m2a": "audio/mpeg",
+                    "m3a": "audio/mpeg",
+                    "oga": "audio/ogg",
+                    "ogg": "audio/ogg",
+                    "spx": "audio/ogg",
+                    "opus": "audio/opus",
+                    "aif": "audio/x-aiff",
+                    "aifc": "audio/x-aiff",
+                    "aiff": "audio/x-aiff",
+                    "flac": "audio/x-flac",
+                    "m4a": "audio/x-m4a",
+                    "m3u": "audio/x-mpegurl",
+                    "wma": "audio/x-ms-wma",
+                    "ra": "audio/x-pn-realaudio",
+                    "wav": "audio/x-wav",
+                    "otf": "font/otf",
+                    "ttf": "font/ttf",
+                    "woff": "font/woff",
+                    "woff2": "font/woff2",
+                    "emf": "image/emf",
+                    "gif": "image/gif",
+                    "heic": "image/heic",
+                    "heif": "image/heif",
+                    "ief": "image/ief",
+                    "jpeg": "image/jpeg",
+                    "jpg": "image/jpeg",
+                    "pict": "image/pict",
+                    "pct": "image/pict",
+                    "pic": "image/pict",
+                    "png": "image/png",
+                    "svg": "image/svg+xml",
+                    "svgz": "image/svg+xml",
+                    "tif": "image/tiff",
+                    "tiff": "image/tiff",
+                    "psd": "image/vnd.adobe.photoshop",
+                    "djvu": "image/vnd.djvu",
+                    "djv": "image/vnd.djvu",
+                    "dwg": "image/vnd.dwg",
+                    "dxf": "image/vnd.dxf",
+                    "dds": "image/vnd.ms-dds",
+                    "webp": "image/webp",
+                    "3ds": "image/x-3ds",
+                    "ras": "image/x-cmu-raster",
+                    "ico": "image/x-icon",
+                    "bmp": "image/x-ms-bmp",
+                    "pnm": "image/x-portable-anymap",
+                    "pbm": "image/x-portable-bitmap",
+                    "pgm": "image/x-portable-graymap",
+                    "ppm": "image/x-portable-pixmap",
+                    "rgb": "image/x-rgb",
+                    "tga": "image/x-tga",
+                    "xbm": "image/x-xbitmap",
+                    "xpm": "image/x-xpixmap",
+                    "xwd": "image/x-xwindowdump",
+                    "eml": "message/rfc822",
+                    "mht": "message/rfc822",
+                    "mhtml": "message/rfc822",
+                    "nws": "message/rfc822",
+                    "obj": "model/obj",
+                    "stl": "model/stl",
+                    "dae": "model/vnd.collada+xml",
+                    "ics": "text/calendar",
+                    "ifb": "text/calendar",
+                    "css": "text/css",
+                    "csv": "text/csv",
+                    "html": "text/html",
+                    "htm": "text/html",
+                    "shtml": "text/html",
+                    "markdown": "text/markdown",
+                    "md": "text/markdown",
+                    "txt": "text/plain",
+                    "text": "text/plain",
+                    "conf": "text/plain",
+                    "def": "text/plain",
+                    "list": "text/plain",
+                    "log": "text/plain",
+                    "in": "text/plain",
+                    "ini": "text/plain",
+                    "rtx": "text/richtext",
+                    "rtf": "text/rtf",
+                    "tsv": "text/tab-separated-values",
+                    "c": "text/x-c",
+                    "cc": "text/x-c",
+                    "cxx": "text/x-c",
+                    "cpp": "text/x-c",
+                    "h": "text/x-c",
+                    "hh": "text/x-c",
+                    "dic": "text/x-c",
+                    "java": "text/x-java-source",
+                    "lua": "text/x-lua",
+                    "py": "text/x-python",
+                    "etx": "text/x-setext",
+                    "sgm": "text/x-sgml",
+                    "sgml": "text/x-sgml",
+                    "vcf": "text/x-vcard",
+                    "xml": "text/xml",
+                    "xul": "text/xul",
+                    "yaml": "text/yaml",
+                    "yml": "text/yaml",
+                    "ts": "video/mp2t",
+                    "mp4": "video/mp4",
+                    "mp4v": "video/mp4",
+                    "mpg4": "video/mp4",
+                    "mpeg": "video/mpeg",
+                    "m1v": "video/mpeg",
+                    "mpa": "video/mpeg",
+                    "mpe": "video/mpeg",
+                    "mpg": "video/mpeg",
+                    "mov": "video/quicktime",
+                    "qt": "video/quicktime",
+                    "webm": "video/webm",
+                    "flv": "video/x-flv",
+                    "m4v": "video/x-m4v",
+                    "asf": "video/x-ms-asf",
+                    "asx": "video/x-ms-asf",
+                    "vob": "video/x-ms-vob",
+                    "wmv": "video/x-ms-wmv",
+                    "avi": "video/x-msvideo",
+                    "*": "video/x-sgi-movie",
+                }[suffix] || '';
+            } catch (e) {
+                console.error(e);
+                return '';
+            }
+        }
+    };
+
+})();