diff --git a/Client/Browser.py b/Client/Browser.py
index 71a48fe..6335bc2 100644
--- a/Client/Browser.py
+++ b/Client/Browser.py
@@ -84,6 +84,11 @@ class Browser(ft.Column):
             spacing=8,
             tight=True,
         )
+        # Shown while uploading: which file, how far (Uploads' progress).
+        self.UploadText = ft.Text("", size=12, color=Palette.Overlay0)
+        self.UploadBar = ft.ProgressBar(value=0, color=Palette.Mauve, bgcolor=Palette.Surface0, bar_height=4)
+        self.UploadRow = ft.Container(ft.Column([self.UploadText, self.UploadBar], spacing=4),
+                                      padding=ft.Padding.symmetric(horizontal=8, vertical=6), visible=False)
         self.EntryList = ft.ListView(expand=True, spacing=2)
         # One shared popup host, opened programmatically (see _RequestMenu).
         # Its built-in triggers can't be switched off, so they're set to
@@ -103,6 +108,7 @@ class Browser(ft.Column):
             # and the breadcrumbs get the rest (and wrap when it's tight).
             ft.Row([ft.Container(self.Breadcrumbs, padding=8, expand=True), ft.Container(self.ActionsToolbar, padding=8)]),
             ft.Divider(height=1, color=Palette.Surface1),
+            self.UploadRow,
             self.FileArea,
         ]
         self._ShowList(Update=False)
@@ -600,19 +606,43 @@ class Browser(ft.Column):
             return
         Saved, Failed = 0, []
         Server = self.TheApp.Server
-        for LocalFile in Paths:
-            if Server:
-                self.TheApp.Notify(f"Uploading {LocalFile.name} ({HumanSize(LocalFile.stat().st_size)})...", "info")
+        Sizes = [LocalFile.stat().st_size if LocalFile.is_file() else 0 for LocalFile in Paths]
+        Total = sum(Sizes)
+        Verb = "Uploading" if Server else "Copying in"
+
+        Shown = [-1, -1]  # (file, percent) on screen: redraw only when it changes
+
+        def ShowProgress(Index: int, Fraction: float) -> None:
+            Done = sum(Sizes[:Index]) + Sizes[Index] * Fraction
+            Percent = int(Done / Total * 100) if Total else 100
+            if Shown == [Index, Percent]:
+                return
+            Shown[:] = [Index, Percent]
+            Of = f" ({Index + 1} of {len(Paths)})" if len(Paths) > 1 else ""
+            self.UploadText.value = (f"{Verb} {Paths[Index].name}{Of}: {Percent}% "
+                                     f"({HumanSize(int(Done))} of {HumanSize(Total)})")
+            self.UploadBar.value = Done / Total if Total else 1
+            self.UploadRow.update()
+
+        self.UploadRow.visible = True
+        for Index, LocalFile in enumerate(Paths):
+            ShowProgress(Index, 0)
             try:
-                await asyncio.to_thread(self.TheApp.Source.Upload, self.Root, self.Path, LocalFile)
+                # Large files go up in chunks and report each one; small ones in one go.
+                await asyncio.to_thread(self.TheApp.Source.Upload, self.Root, self.Path, LocalFile,
+                                        lambda Fraction, I=Index: ShowProgress(I, Fraction))
                 Saved += 1
             except SourceError as Error:
                 if Error.Status == 401:
+                    self.UploadRow.visible = False
+                    self.UploadRow.update()
                     self.TheApp.HandleError(Error)
                     return
                 Failed.append(f"{LocalFile.name}: {Error}")
             except OSError as Error:
                 Failed.append(f"{LocalFile.name}: {Error}")
+        self.UploadRow.visible = False
+        self.UploadRow.update()
         self.Refresh()
         if Failed:
             self.TheApp.Notify("Couldn't upload " + "; ".join(Failed), "error")
diff --git a/Client/Sources.py b/Client/Sources.py
index 0afcd23..bc3200d 100644
--- a/Client/Sources.py
+++ b/Client/Sources.py
@@ -5,6 +5,7 @@ entries shaped like the server's /api/tree items, so the rest of the client
 never needs to know which one it's talking to."""
 
 import fnmatch
+import io
 import shutil
 import uuid
 from dataclasses import dataclass
@@ -412,7 +413,8 @@ class ServerSource(Source):
         Params = self._At(Root, DirectoryPath)
         if Size <= ChunkedUploadThresholdBytes:
             with LocalFile.open("rb") as Handle:
-                Result = self._Json("POST", "/upload", params=Params, files=[("Files", (LocalFile.name, Handle))])
+                Sending = _CountingReader(Handle, Size, OnProgress) if OnProgress else Handle
+                Result = self._Json("POST", "/upload", params=Params, files=[("Files", (LocalFile.name, Sending))])
             if Result.get("Errors"):
                 raise SourceError("; ".join(Result["Errors"]))
             return Result["Saved"][0]
@@ -423,10 +425,13 @@ class ServerSource(Source):
             for ChunkIndex in range(TotalChunks):
                 ChunkParams = {**Params, "UploadId": UploadId, "ChunkIndex": ChunkIndex,
                                "TotalChunks": TotalChunks, "FileName": LocalFile.name}
-                self._Request("POST", "/upload/chunk", params=ChunkParams,
-                              files=[("Chunk", ("chunk", Handle.read(UploadChunkSizeBytes)))])
+                Chunk = Handle.read(UploadChunkSizeBytes)
+                Sending = io.BytesIO(Chunk)
                 if OnProgress:
-                    OnProgress((ChunkIndex + 1) / TotalChunks)
+                    Before = ChunkIndex * UploadChunkSizeBytes
+                    Sending = _CountingReader(Sending, len(Chunk),
+                                              lambda Fraction, B=Before, L=len(Chunk): OnProgress((B + L * Fraction) / Size))
+                self._Request("POST", "/upload/chunk", params=ChunkParams, files=[("Chunk", ("chunk", Sending))])
         Done = {**Params, "UploadId": UploadId, "TotalChunks": TotalChunks, "FileName": LocalFile.name}
         return self._Json("POST", "/upload/complete", params=Done)["Saved"]
 
@@ -474,5 +479,26 @@ class ServerSource(Source):
         return self._Request("POST", "/diagram", json=Body).content
 
 
+class _CountingReader:
+    """A file handle that reports how much of it has been read (sent): httpx
+    reads an upload's file in pieces, so this is its progress."""
+
+    def __init__(self, Handle, Size: int, OnProgress: Callable[[float], None]):
+        self._Handle = Handle
+        self._Size = Size
+        self._OnProgress = OnProgress
+        self._Sent = 0
+
+    def read(self, Count: int = -1) -> bytes:
+        Data = self._Handle.read(Count)
+        self._Sent += len(Data)
+        if self._Size:
+            self._OnProgress(min(1.0, self._Sent / self._Size))
+        return Data
+
+    def __getattr__(self, Name: str):
+        return getattr(self._Handle, Name)  # seek, tell, fileno: for the length
+
+
 def MakeSource(Config: AppConfig, Token: str = "") -> Source:
     return ServerSource(Config, Token) if Config.Mode == "Server" else LocalSource(Config)
diff --git a/Frontend/src/Api.js b/Frontend/src/Api.js
index a99dbf7..b092f9a 100644
--- a/Frontend/src/Api.js
+++ b/Frontend/src/Api.js
@@ -171,18 +171,41 @@ export function GetDownloadUrl(RootName, RelativePath) {
   return `${ApiBase}/download?${Params}`;
 }
 
-export async function UploadFiles(RootName, RelativePath, Files) {
+// Uploads go through XMLHttpRequest: unlike fetch, it reports how much has
+// been sent. OnProgress(BytesSent) is optional.
+function PostFormWithProgress(Url, Form, OnProgress) {
+  return new Promise((Resolve, Reject) => {
+    const Request = new XMLHttpRequest();
+    Request.open("POST", Url);
+    Request.withCredentials = true;
+    if (OnProgress) {
+      Request.upload.onprogress = (Event) => OnProgress(Event.loaded);
+    }
+    Request.onload = () => {
+      let Body = null;
+      try {
+        Body = JSON.parse(Request.responseText);
+      } catch {
+        Body = null;
+      }
+      if (Request.status >= 200 && Request.status < 300) {
+        Resolve(Body);
+      } else {
+        Reject(new Error(Body && Body.detail ? Body.detail : Request.statusText || `Upload failed (${Request.status})`));
+      }
+    };
+    Request.onerror = () => Reject(new Error("Upload failed: couldn't reach the server."));
+    Request.send(Form);
+  });
+}
+
+export function UploadFiles(RootName, RelativePath, Files, OnProgress) {
   const Form = new FormData();
   for (const File of Files) {
     Form.append("Files", File);
   }
   const Params = new URLSearchParams({ Root: RootName, Path: RelativePath });
-  const Response = await fetch(`${ApiBase}/upload?${Params}`, {
-    method: "POST",
-    credentials: "same-origin",
-    body: Form,
-  });
-  return ParseJsonOrThrow(Response);
+  return PostFormWithProgress(`${ApiBase}/upload?${Params}`, Form, OnProgress);
 }
 
 const UploadChunkSizeBytes = 20 * 1024 * 1024;
@@ -199,7 +222,7 @@ function GenerateUploadId() {
   return `${Date.now()}-${Math.random().toString(16).slice(2)}`;
 }
 
-async function UploadFileChunk(RootName, RelativePath, UploadId, ChunkIndex, TotalChunks, FileName, ChunkBlob) {
+function UploadFileChunk(RootName, RelativePath, UploadId, ChunkIndex, TotalChunks, FileName, ChunkBlob, OnProgress) {
   const Form = new FormData();
   Form.append("Chunk", ChunkBlob, "chunk");
   const Params = new URLSearchParams({
@@ -210,12 +233,7 @@ async function UploadFileChunk(RootName, RelativePath, UploadId, ChunkIndex, Tot
     TotalChunks: String(TotalChunks),
     FileName,
   });
-  const Response = await fetch(`${ApiBase}/upload/chunk?${Params}`, {
-    method: "POST",
-    credentials: "same-origin",
-    body: Form,
-  });
-  return ParseJsonOrThrow(Response);
+  return PostFormWithProgress(`${ApiBase}/upload/chunk?${Params}`, Form, OnProgress);
 }
 
 function CompleteChunkedUpload(RootName, RelativePath, UploadId, TotalChunks, FileName) {
@@ -229,14 +247,16 @@ function CompleteChunkedUpload(RootName, RelativePath, UploadId, TotalChunks, Fi
   return FetchJson(`/upload/complete?${Params}`, { method: "POST" });
 }
 
-export async function UploadFileChunked(RootName, RelativePath, File) {
+// OnProgress(BytesSent) counts across all the chunks.
+export async function UploadFileChunked(RootName, RelativePath, File, OnProgress) {
   const UploadId = GenerateUploadId();
   const TotalChunks = Math.max(1, Math.ceil(File.size / UploadChunkSizeBytes));
 
   for (let ChunkIndex = 0; ChunkIndex < TotalChunks; ChunkIndex++) {
     const Start = ChunkIndex * UploadChunkSizeBytes;
     const ChunkBlob = File.slice(Start, Start + UploadChunkSizeBytes);
-    await UploadFileChunk(RootName, RelativePath, UploadId, ChunkIndex, TotalChunks, File.name, ChunkBlob);
+    await UploadFileChunk(RootName, RelativePath, UploadId, ChunkIndex, TotalChunks, File.name, ChunkBlob,
+      OnProgress && ((Sent) => OnProgress(Start + Math.min(Sent, ChunkBlob.size))));
   }
 
   return CompleteChunkedUpload(RootName, RelativePath, UploadId, TotalChunks, File.name);
diff --git a/Frontend/src/App.jsx b/Frontend/src/App.jsx
index 1ae57a4..81c96ba 100644
--- a/Frontend/src/App.jsx
+++ b/Frontend/src/App.jsx
@@ -9,6 +9,7 @@ import SettingsPanel from "./Components/SettingsPanel.jsx";
 import GraphPane from "./Components/GraphPane.jsx";
 import LoginScreen from "./Components/LoginScreen.jsx";
 import ErrorToast from "./Components/ErrorToast.jsx";
+import UploadToast from "./Components/UploadToast.jsx";
 import {
   EnsureDirectoryNote,
   FetchAuthStatus,
@@ -429,6 +430,7 @@ export default function App() {
           OnProfileUpdated={HandleProfileUpdated}
         />
       )}
+      <UploadToast />
       <ErrorToast Message={ErrorMessage} OnDismiss={() => SetErrorMessage(null)} />
     </div>
   );
diff --git a/Frontend/src/Components/DirectoryPane.jsx b/Frontend/src/Components/DirectoryPane.jsx
index fd397ad..eadeaa8 100644
--- a/Frontend/src/Components/DirectoryPane.jsx
+++ b/Frontend/src/Components/DirectoryPane.jsx
@@ -7,13 +7,11 @@ import {
   FetchLock,
   FetchTree,
   GetDownloadUrl,
-  IsLargeUpload,
   MoveEntry,
   RenameEntry,
   SetLock as SetLockApi,
-  UploadFileChunked,
-  UploadFiles,
 } from "../Api.js";
+import { UploadAll } from "../Upload.js";
 import { GetFileIcon, GetFolderIcon } from "../IconStyle.js";
 import AccessModal from "./AccessModal.jsx";
 import PromptModal from "./PromptModal.jsx";
@@ -183,30 +181,7 @@ export default function DirectoryPane({
   async function HandleUpload(Files) {
     if (!Files || Files.length === 0) return;
 
-    const FileArray = Array.from(Files);
-    const SmallFiles = FileArray.filter((File) => !IsLargeUpload(File));
-    const LargeFiles = FileArray.filter((File) => IsLargeUpload(File));
-    const Errors = [];
-
-    if (SmallFiles.length > 0) {
-      try {
-        const Result = await UploadFiles(RootName, DirectoryPath, SmallFiles);
-        if (Result.Errors && Result.Errors.length > 0) {
-          Errors.push(...Result.Errors);
-        }
-      } catch (Error) {
-        Errors.push(Error.message);
-      }
-    }
-
-    for (const File of LargeFiles) {
-      try {
-        await UploadFileChunked(RootName, DirectoryPath, File);
-      } catch (Error) {
-        Errors.push(`${File.name}: ${Error.message}`);
-      }
-    }
-
+    const Errors = await UploadAll(RootName, DirectoryPath, Files);
     if (Errors.length > 0) {
       SetErrorMessage(Errors.join("; "));
     }
diff --git a/Frontend/src/Components/Sidebar.jsx b/Frontend/src/Components/Sidebar.jsx
index 644b41f..cb00ba4 100644
--- a/Frontend/src/Components/Sidebar.jsx
+++ b/Frontend/src/Components/Sidebar.jsx
@@ -8,13 +8,11 @@ import {
   FetchTree,
   GetAvatarUrl,
   GetDownloadUrl,
-  IsLargeUpload,
   MoveEntry,
   RenameEntry,
   SetLock as SetLockApi,
-  UploadFileChunked,
-  UploadFiles,
 } from "../Api.js";
+import { UploadAll } from "../Upload.js";
 import { GetFileIcon, GetFolderIcon } from "../IconStyle.js";
 import AccessModal from "./AccessModal.jsx";
 import PromptModal from "./PromptModal.jsx";
@@ -386,30 +384,7 @@ export default function Sidebar({
   async function HandleUpload(Files) {
     if (!Files || Files.length === 0) return;
 
-    const FileArray = Array.from(Files);
-    const SmallFiles = FileArray.filter((File) => !IsLargeUpload(File));
-    const LargeFiles = FileArray.filter((File) => IsLargeUpload(File));
-    const Errors = [];
-
-    if (SmallFiles.length > 0) {
-      try {
-        const Result = await UploadFiles(RootName, CurrentDirectoryPath, SmallFiles);
-        if (Result.Errors && Result.Errors.length > 0) {
-          Errors.push(...Result.Errors);
-        }
-      } catch (Error) {
-        Errors.push(Error.message);
-      }
-    }
-
-    for (const File of LargeFiles) {
-      try {
-        await UploadFileChunked(RootName, CurrentDirectoryPath, File);
-      } catch (Error) {
-        Errors.push(`${File.name}: ${Error.message}`);
-      }
-    }
-
+    const Errors = await UploadAll(RootName, CurrentDirectoryPath, Files);
     if (Errors.length > 0) {
       SetErrorMessage(Errors.join("; "));
     }
diff --git a/Frontend/src/Components/UploadToast.jsx b/Frontend/src/Components/UploadToast.jsx
new file mode 100644
index 0000000..5159977
--- /dev/null
+++ b/Frontend/src/Components/UploadToast.jsx
@@ -0,0 +1,26 @@
+import React, { useSyncExternalStore } from "react";
+
+import { FormatSize, GetUploadState, SubscribeUploads } from "../Upload.js";
+
+export default function UploadToast() {
+  const State = useSyncExternalStore(SubscribeUploads, GetUploadState);
+  if (!State) return null;
+
+  const Files = `${State.Count} file${State.Count === 1 ? "" : "s"}`;
+  const Percent = State.Total > 0 ? Math.floor((State.Done / State.Total) * 100) : 100;
+
+  return (
+    <div className="UploadToast" role="status">
+      <span>
+        {State.Finished
+          ? `Uploaded ${Files}.`
+          : `Uploading ${Files}: ${Percent}% (${FormatSize(State.Done)} of ${FormatSize(State.Total)})`}
+      </span>
+      {!State.Finished && (
+        <div className="UploadToastBar">
+          <div className="UploadToastFill" style={{ width: `${Percent}%` }} />
+        </div>
+      )}
+    </div>
+  );
+}
diff --git a/Frontend/src/Styles/Theme.css b/Frontend/src/Styles/Theme.css
index bba6ebf..48f2bf7 100644
--- a/Frontend/src/Styles/Theme.css
+++ b/Frontend/src/Styles/Theme.css
@@ -1135,6 +1135,38 @@ img,
   z-index: 200;
 }
 
+.UploadToast {
+  position: fixed;
+  bottom: calc(20px + env(safe-area-inset-bottom, 0px));
+  left: 50%;
+  transform: translateX(-50%);
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  min-width: 260px;
+  max-width: 480px;
+  padding: 10px 14px;
+  background: var(--Surface);
+  border: 1px solid var(--Purple);
+  border-radius: 6px;
+  color: var(--Text);
+  font-size: 13px;
+  z-index: 200;
+}
+
+.UploadToastBar {
+  height: 4px;
+  background: var(--SurfaceAlt);
+  border-radius: 2px;
+  overflow: hidden;
+}
+
+.UploadToastFill {
+  height: 100%;
+  background: var(--Purple);
+  transition: width 0.2s ease;
+}
+
 .ErrorToastClose {
   background: none;
   border: none;
diff --git a/Frontend/src/Upload.js b/Frontend/src/Upload.js
new file mode 100644
index 0000000..aab7643
--- /dev/null
+++ b/Frontend/src/Upload.js
@@ -0,0 +1,95 @@
+// Uploading files, with progress: the sidebar and the directory pane both
+// upload through UploadAll, and UploadToast.jsx shows how it's going
+// ("Uploading 3 files: 45% (12 MB of 27 MB)", then "Uploaded 3 files.").
+// Small files go up together, large ones in chunks (Api.js).
+
+import { IsLargeUpload, UploadFileChunked, UploadFiles } from "./Api.js";
+
+let State = null; // { Count, Done, Total (bytes), Finished }
+let ActiveUploads = 0;
+const Listeners = new Set();
+
+function Publish(Next) {
+  State = Next;
+  Listeners.forEach((Listener) => Listener());
+}
+
+export function SubscribeUploads(Listener) {
+  Listeners.add(Listener);
+  return () => Listeners.delete(Listener);
+}
+
+export function GetUploadState() {
+  return State;
+}
+
+export function FormatSize(Bytes) {
+  const Units = ["B", "KB", "MB", "GB", "TB"];
+  let Size = Bytes;
+  let Unit = 0;
+  while (Size >= 1024 && Unit < Units.length - 1) {
+    Size /= 1024;
+    Unit++;
+  }
+  return `${Unit === 0 ? Size : Size.toFixed(1)} ${Units[Unit]}`;
+}
+
+// Closing the tab mid-upload would lose it, so ask first.
+window.addEventListener("beforeunload", (Event) => {
+  if (ActiveUploads > 0) {
+    Event.preventDefault();
+    Event.returnValue = "";
+  }
+});
+
+// Uploads Files into DirectoryPath; returns the errors (empty if all went up).
+export async function UploadAll(RootName, DirectoryPath, Files) {
+  const FileArray = Array.from(Files || []);
+  if (FileArray.length === 0) return [];
+
+  const SmallFiles = FileArray.filter((File) => !IsLargeUpload(File));
+  const LargeFiles = FileArray.filter((File) => IsLargeUpload(File));
+  const Total = FileArray.reduce((Sum, File) => Sum + File.size, 0);
+  const Errors = [];
+  let Finished = 0; // bytes of the parts already done
+
+  const Report = (Current) =>
+    Publish({ Count: FileArray.length, Done: Math.min(Total, Finished + Current), Total, Finished: false });
+
+  ActiveUploads++;
+  Report(0);
+  try {
+    if (SmallFiles.length > 0) {
+      try {
+        const Result = await UploadFiles(RootName, DirectoryPath, SmallFiles, Report);
+        if (Result.Errors && Result.Errors.length > 0) {
+          Errors.push(...Result.Errors);
+        }
+      } catch (Error) {
+        Errors.push(Error.message);
+      }
+      Finished += SmallFiles.reduce((Sum, File) => Sum + File.size, 0);
+    }
+
+    for (const File of LargeFiles) {
+      try {
+        await UploadFileChunked(RootName, DirectoryPath, File, Report);
+      } catch (Error) {
+        Errors.push(`${File.name}: ${Error.message}`);
+      }
+      Finished += File.size;
+    }
+  } finally {
+    ActiveUploads--;
+  }
+
+  // Errors show in the error toast instead; a success stays up for a moment.
+  const Done = { Count: FileArray.length, Done: Total, Total, Finished: true };
+  Publish(Errors.length > 0 ? null : Done);
+  if (Errors.length === 0) {
+    setTimeout(() => {
+      if (State === Done) Publish(null);
+    }, 3000);
+  }
+  return Errors;
+}