diff --git a/README.md b/README.md
index 43c0e1a3..f0bf7976 100644
--- a/README.md
+++ b/README.md
@@ -278,6 +278,9 @@ some improvement ideas
 * VirtualBox: sqlite throws `Disk I/O Error` when running in a VM and the up2k database is in a vboxsf
   * use `--hist` or the `hist` volflag (`-v [...]:c,hist=/tmp/foo`) to place the db inside the vm instead
 
+* Ubuntu: dragging files from certain folders into firefox or chrome is impossible
+  * due to snap security policies -- see `snap connections firefox` for the allowlist, `removable-media` permits all of `/mnt` and `/media` apparently
+
 
 # FAQ
 
diff --git a/copyparty/web/browser.js b/copyparty/web/browser.js
index a7b0ed6a..5d9d19b9 100644
--- a/copyparty/web/browser.js
+++ b/copyparty/web/browser.js
@@ -304,6 +304,7 @@ var Ls = {
 		"u_badf": 'These {0} files (of {1} total) were skipped, possibly due to filesystem permissions:\n\n',
 		"u_blankf": 'These {0} files (of {1} total) are blank / empty; upload them anyways?\n\n',
 		"u_just1": '\nMaybe it works better if you select just one file',
+		"u_ff_many": "This amount of files <em>may</em> cause Firefox to skip some files, or crash.\nPlease try again with fewer files (or use Chrome) if that happens.\n\n",
 		"u_asku": 'upload these {0} files to <code>{1}</code>',
 		"u_unpt": "you can undo / delete this upload using the top-left 🧯",
 		"u_etadone": 'Done ({0}, {1} files)',
@@ -646,6 +647,7 @@ var Ls = {
 		"u_badf": 'Disse {0} filene (av totalt {1}) kan ikke leses, kanskje pga rettighetsproblemer i filsystemet på datamaskinen din:\n\n',
 		"u_blankf": 'Disse {0} filene (av totalt {1}) er blanke / uten innhold; ønsker du å laste dem opp uansett?\n\n',
 		"u_just1": '\nFunker kanskje bedre hvis du bare tar én fil om gangen',
+		"u_ff_many": "Det var mange filer! Mulig at Firefox kommer til å krasje, eller\nhoppe over et par av dem. Smart å ha Chrome på lur i tilfelle.\n\n",
 		"u_asku": 'Laste opp disse {0} filene til <code>{1}</code>',
 		"u_unpt": "Du kan angre / slette opplastningen med 🧯 oppe til venstre",
 		"u_etadone": 'Ferdig ({0}, {1} filer)',
diff --git a/copyparty/web/up2k.js b/copyparty/web/up2k.js
index c4eadda7..154e870f 100644
--- a/copyparty/web/up2k.js
+++ b/copyparty/web/up2k.js
@@ -1177,7 +1177,12 @@ function up2k_init(subtle) {
             return a < b ? -1 : a > b ? 1 : 0;
         });
 
-        var msg = [L.u_asku.format(good_files.length, esc(get_vpath())) + '<ul>'];
+        var msg = [];
+
+        if (FIREFOX && good_files.length > 5000)
+            msg.push(L.u_ff_many);
+
+        msg.push(L.u_asku.format(good_files.length, esc(get_vpath())) + '<ul>');
         for (var a = 0, aa = Math.min(20, good_files.length); a < aa; a++)
             msg.push('<li>' + esc(good_files[a][1]) + '</li>');
 
diff --git a/copyparty/web/util.js b/copyparty/web/util.js
index d0c8595a..e6e47bee 100644
--- a/copyparty/web/util.js
+++ b/copyparty/web/util.js
@@ -13,6 +13,7 @@ var wah = '',
     TOUCH = 'ontouchstart' in window,
     MOBILE = TOUCH,
     CHROME = !!window.chrome,
+    FIREFOX = ('netscape' in window) && / rv:/.test(navigator.userAgent),
     IPHONE = TOUCH && /iPhone|iPad|iPod/i.test(navigator.userAgent),
     WINDOWS = navigator.platform ? navigator.platform == 'Win32' : /Windows/.test(navigator.userAgent);