diff --git a/contrib/plugins/up2k-hooks.js b/contrib/plugins/up2k-hooks.js
new file mode 100644
index 00000000..dedf54e0
--- /dev/null
+++ b/contrib/plugins/up2k-hooks.js
@@ -0,0 +1,45 @@
+// hooks into up2k
+
+function up2k_namefilter(good_files, nil_files, bad_files, hooks) {
+    // is called when stuff is dropped into the browser,
+    // after iterating through the directory tree and discovering all files,
+    // before the upload confirmation dialogue is shown
+
+    // good_files will successfully upload
+    // nil_files are empty files and will show an alert in the final hook
+    // bad_files are unreadable and cannot be uploaded
+    var file_lists = [good_files, nil_files, bad_files];
+
+    // build a list of filenames
+    var filenames = [];
+    for (var lst of file_lists)
+        for (var ent of lst)
+            filenames.push(ent[1]);
+
+    toast.inf(5, "running database query...");
+
+    // simulate delay while passing the list to some api for checking
+    setTimeout(function () {
+
+        // only keep webm files as an example
+        var new_lists = [];
+        for (var lst of file_lists) {
+            var keep = [];
+            new_lists.push(keep);
+
+            for (var ent of lst)
+                if (/\.webm$/.test(ent[1]))
+                    keep.push(ent);
+        }
+
+        // finally, call the next hook in the chain
+        [good_files, nil_files, bad_files] = new_lists;
+        hooks[0](good_files, nil_files, bad_files, hooks.slice(1));
+
+    }, 1000);
+}
+
+// register
+up2k_hooks.push(function () {
+    up2k.gotallfiles.unshift(up2k_namefilter);
+});
diff --git a/copyparty/web/up2k.js b/copyparty/web/up2k.js
index 2fdc1971..24ff1b75 100644
--- a/copyparty/web/up2k.js
+++ b/copyparty/web/up2k.js
@@ -15,6 +15,7 @@ function goto_up2k() {
 // chrome requires https to use crypto.subtle,
 // usually it's undefined but some chromes throw on invoke
 var up2k = null,
+    up2k_hooks = [],
     sha_js = window.WebAssembly ? 'hw' : 'ac',  // ff53,c57,sa11
     m = 'will use ' + sha_js + ' instead of native sha512 due to';
 
@@ -578,6 +579,12 @@ function fsearch_explain(n) {
 
 
 function up2k_init(subtle) {
+    var r = {
+        "init_deps": init_deps,
+        "set_fsearch": set_fsearch,
+        "gotallfiles": [gotallfiles]  // hooks
+    };
+
     function showmodal(msg) {
         ebi('u2notbtn').innerHTML = msg;
         ebi('u2btn').style.display = 'none';
@@ -696,6 +703,10 @@ function up2k_init(subtle) {
     var pvis = new U2pvis("bz", '#u2cards', uc),
         donut = new Donut(uc, st);
 
+    r.ui = pvis;
+    r.st = st;
+    r.uc = uc;
+
     var bobslice = null;
     if (window.File)
         bobslice = File.prototype.slice || File.prototype.mozSlice || File.prototype.webkitSlice;
@@ -906,7 +917,8 @@ function up2k_init(subtle) {
 
         if (!dirs.length) {
             if (!pf.length)
-                return gotallfiles(good, nil, bad);
+                // call first hook, pass list of remaining hooks to call
+                return r.gotallfiles[0](good, nil, bad, r.gotallfiles.slice(1));
 
             console.log("retry pf, " + pf.length);
             setTimeout(function () {
@@ -2123,7 +2135,12 @@ function up2k_init(subtle) {
     if (parallel_uploads < 1)
         bumpthread(1);
 
-    return { "init_deps": init_deps, "set_fsearch": set_fsearch, "ui": pvis, "st": st, "uc": uc }
+    setTimeout(function () {
+        for (var a = 0; a < up2k_hooks.length; a++)
+            up2k_hooks[a]();
+    }, 1);
+
+    return r;
 }