diff --git a/frontend/src/APIConnection.ts b/frontend/src/APIConnection.ts
index a7f42def..828cd839 100644
--- a/frontend/src/APIConnection.ts
+++ b/frontend/src/APIConnection.ts
@@ -1,5 +1,3 @@
-import {UpdateResult} from "./UserProfile";
-
 export type User = {
   url: string;
   id: number;
@@ -36,6 +34,19 @@ export type CachedAPIResponse<T extends SingleAPIResponse> = {
   parents: string[];
 }
 
+export type APIMessage = {
+  severity: "error" | "warning" | "info" | "success";
+  message: string;
+  context?: any;
+}
+
+export type MessageHandler = (message: APIMessage) => void
+
+export type ConnectionProps = {
+  base_url?: string;
+  message_handlers?: MessageHandler[];
+}
+
 function clean_url(url: string, baseURL: string): string {
   url = url.toLowerCase();
   if (!url.startsWith(baseURL))
@@ -97,15 +108,29 @@ class ResponseCache {
   }
 }
 
+/**
+ * @class
+ * APIConnection manages a connection to the backend REST API.
+ * It handles user management directly, and offers a modified
+ * fetch interface for everything else.
+ *
+ * Results are cached and can be referenced directly with their
+ * canonical URL and indirectly with a parent URL.
+ */
 export class APIConnection {
   url: string = 'http://localhost:5000/'.toLowerCase()
   user: User | null = null
   cache_expiry_time = 60_000 // 1 minute
   results: ResponseCache
   cookies: any
+  message_handlers: MessageHandler[] = []
 
-  constructor() {
-    console.info("Spawn API connection")
+  constructor(props?: ConnectionProps) {
+    if (props?.base_url)
+      this.url = props.base_url
+    if (props?.message_handlers)
+      this.message_handlers = props.message_handlers
+    console.info(`Spawn API connection (${this.url})`)
     const local_user = window.localStorage.getItem('user')
     if (local_user)
       this.user = JSON.parse(local_user)
@@ -128,7 +153,7 @@ export class APIConnection {
       })
   }
 
-  update_user(email: string, password: string, currentPassword: string): Promise<UpdateResult> {
+  update_user(email: string, password: string, currentPassword: string): Promise<APIMessage> {
     if (!this.user)
       return new Promise(() => {})
     return fetch(
@@ -149,9 +174,9 @@ export class APIConnection {
             .then(user => {
               this.user = {...user, token: this.user?.token}
             })
-            .then(() => ({success: true, message: 'Updated successfully'}))
+            .then(() => ({severity: "success", message: 'Updated successfully'}))
         return r.json()
-          .then(r => ({success: false, message: r.error}))
+          .then(r => ({severity: "error", message: r.error}))
       })
   }
 
@@ -179,26 +204,10 @@ export class APIConnection {
     return fetch(this.url + "logout/", {method: 'POST'})
   }
 
-  get_cookie(name: string) {
-    const value = `; ${document.cookie}`;
-    const parts = value.split(`; ${name}=`);
-    if (parts.length === 2) return parts?.pop()?.split(';').shift();
-    return null
-  }
-
   get is_logged_in() {
     return !!this.user?.token
   }
 
-  async get_is_logged_in(skip: boolean = true): Promise<boolean> {
-    await this.login('admin', 'admin')
-    const cookie = this.get_cookie('csrf_access_token');
-    if (cookie === undefined || !this.user)
-      if (!skip)
-        return this.get_is_logged_in(false);
-    return cookie !== undefined && this.user !== null;
-  }
-
   _prepare_fetch_headers(url: string, options?: any) {
     if (!this.is_logged_in)
       throw new Error(`Cannot fetch ${url}: not logged on.`)
@@ -230,9 +239,15 @@ export class APIConnection {
           return null;
         return response.json() as Promise<T|T[]>;
       })
+      .catch(e => {
+        this.message_handlers.forEach(h => h({severity: "error", message: e.message, context: e}))
+        return url
+      })
       .then(json => {
         if (void_cache)
           this.results.purge(parent)
+        if (typeof json === "string")
+          return json
         if (json === null) {
           this.results.remove(url)
           return url
diff --git a/frontend/src/AsyncTable.tsx b/frontend/src/AsyncTable.tsx
index 24106b2f..f13b7919 100644
--- a/frontend/src/AsyncTable.tsx
+++ b/frontend/src/AsyncTable.tsx
@@ -186,7 +186,7 @@ export default class AsyncTable<T extends APIObject> extends Component<AsyncTabl
       )
   }
 
-  update_all = async (use_cache: boolean = true) => {
+  update_all = async (use_cache: boolean = false) => {
     this.reset_new_row()
     return this.get_data(this.props.url, use_cache)
   }
diff --git a/frontend/src/Core.tsx b/frontend/src/Core.tsx
index 89c3f5ba..5597dd2a 100644
--- a/frontend/src/Core.tsx
+++ b/frontend/src/Core.tsx
@@ -39,10 +39,12 @@ import ListItem from '@mui/material/ListItem';
 import ListItemIcon from '@mui/material/ListItemIcon';
 import ListItemText from '@mui/material/ListItemText';
 import { ReactComponent as GalvanalyserLogo } from './Galvanalyser-logo.svg';
-import Connection from "./APIConnection";
+import Connection, {APIMessage} from "./APIConnection";
 import Stack from "@mui/material/Stack";
 import Tokens from "./Tokens";
 import UserProfile from "./UserProfile";
+import Snackbar from "@mui/material/Snackbar";
+import Alert from "@mui/material/Alert";
 
 const PrivateRoute = (component: JSX.Element) => {
   const logged = Connection.is_logged_in;
@@ -82,7 +84,7 @@ const useStyles = makeStyles((theme) => ({
     }),
   },
   galvanalyserLogo: {
-    height: '40px' 
+    height: '40px'
   },
   menuButton: {
     marginRight: 36,
@@ -164,35 +166,48 @@ export default function Core() {
     setOpen(false);
   };
 
+  const [snackbarOpen, setSnackbarOpen] = React.useState<boolean>(false)
+  const [apiMessage, setAPIMessage] = React.useState<APIMessage|null>(null)
+  const handleSnackbarClose = (e: any, reason?: string) => {
+    if (reason !== 'clickaway') {
+      setSnackbarOpen(false)
+      setAPIMessage(null)
+    }
+  }
+  Connection.message_handlers.push((h) => {
+    setAPIMessage(h)
+    setSnackbarOpen(true)
+  })
+
   const mainListItems = (
     <Stack>
-      <ListItem button 
-        selected={isDatasetPath} 
-        component={Link} to={datasetsPath}>
+      <ListItem button
+                selected={isDatasetPath}
+                component={Link} to={datasetsPath}>
         <ListItemIcon>
           <TableChartIcon />
         </ListItemIcon>
         <ListItemText primary="Datasets" />
       </ListItem>
-      <ListItem button 
-        selected={isHarvestersPath} 
-        component={Link} to={harvestersPath}>
+      <ListItem button
+                selected={isHarvestersPath}
+                component={Link} to={harvestersPath}>
         <ListItemIcon>
           <BackupIcon />
         </ListItemIcon>
         <ListItemText primary="Harvesters" />
       </ListItem>
-      <ListItem button 
-        selected={isCellsPath} 
-        component={Link} to={cellsPath}>
+      <ListItem button
+                selected={isCellsPath}
+                component={Link} to={cellsPath}>
         <ListItemIcon>
           <BatteryUnknownIcon />
         </ListItemIcon>
         <ListItemText primary="Cells" />
       </ListItem>
-      <ListItem button 
-        selected={isEquipmentPath} 
-        component={Link} to={equipmentPath}>
+      <ListItem button
+                selected={isEquipmentPath}
+                component={Link} to={equipmentPath}>
         <ListItemIcon>
           <SpeedIcon/>
         </ListItemIcon>
@@ -214,78 +229,83 @@ export default function Core() {
 
   const Layout = (
     <div className={classes.root}>
-    <CssBaseline />
-    <AppBar position="absolute" className={clsx(classes.appBar, open && classes.appBarShift)}>
-      <Toolbar className={classes.toolbar}>
-        <IconButton
-          edge="start"
-          color="inherit"
-          aria-label="open drawer"
-          onClick={handleDrawerOpen}
-          className={clsx(classes.menuButton, open && classes.menuButtonHidden)}
-        >
-          <MenuIcon />
-        </IconButton>
-        <GalvanalyserLogo className={classes.galvanalyserLogo}/>
-        <Typography component="h1" variant="h6" color="inherit" noWrap className={classes.title}>
-        </Typography>
+      <CssBaseline />
+      <AppBar position="absolute" className={clsx(classes.appBar, open && classes.appBarShift)}>
+        <Toolbar className={classes.toolbar}>
+          <IconButton
+            edge="start"
+            color="inherit"
+            aria-label="open drawer"
+            onClick={handleDrawerOpen}
+            className={clsx(classes.menuButton, open && classes.menuButtonHidden)}
+          >
+            <MenuIcon />
+          </IconButton>
+          <GalvanalyserLogo className={classes.galvanalyserLogo}/>
+          <Typography component="h1" variant="h6" color="inherit" noWrap className={classes.title}>
+          </Typography>
 
-        <Button color="inherit" >
-          User: {userDisplayName}
-        </Button>
-        <Button color="inherit" onClick={() => {
-          navigate(profilePath)
-        }}>
-          Manage Profile
-        </Button>
-        <Button color="inherit" onClick={() => {
-          navigate(tokenPath)
-        }}>
-          Manage API Tokens
-        </Button>
-        <Button color="inherit" onClick={() => {
-          Connection.logout().then(()=> {navigate('/login');});
-        }}>
-          Logout
-        </Button>
-      </Toolbar>
-    </AppBar>
-    <Drawer
-      variant="permanent"
-      classes={{
-        paper: clsx(classes.drawerPaper, !open && classes.drawerPaperClose),
-      }}
-      open={open}
-    >
-      <div className={classes.toolbarIcon}>
-        <IconButton onClick={handleDrawerClose}>
-          <ChevronLeftIcon />
-        </IconButton>
-      </div>
-      <Divider />
-      <List>{mainListItems}</List>
-    </Drawer>
-    <main className={classes.content}>
-      <div className={classes.appBarSpacer} />
+          <Button color="inherit" >
+            User: {userDisplayName}
+          </Button>
+          <Button color="inherit" onClick={() => {
+            navigate(profilePath)
+          }}>
+            Manage Profile
+          </Button>
+          <Button color="inherit" onClick={() => {
+            navigate(tokenPath)
+          }}>
+            Manage API Tokens
+          </Button>
+          <Button color="inherit" onClick={() => {
+            Connection.logout().then(()=> {navigate('/login');});
+          }}>
+            Logout
+          </Button>
+        </Toolbar>
+      </AppBar>
+      <Drawer
+        variant="permanent"
+        classes={{
+          paper: clsx(classes.drawerPaper, !open && classes.drawerPaperClose),
+        }}
+        open={open}
+      >
+        <div className={classes.toolbarIcon}>
+          <IconButton onClick={handleDrawerClose}>
+            <ChevronLeftIcon />
+          </IconButton>
+        </div>
+        <Divider />
+        <List>{mainListItems}</List>
+      </Drawer>
+      <main className={classes.content}>
+        <div className={classes.appBarSpacer} />
         <Outlet />
-    </main>
+      </main>
+      <Snackbar open={snackbarOpen} autoHideDuration={6000} onClose={handleSnackbarClose}>
+        <Alert onClose={handleSnackbarClose} severity={apiMessage?.severity} sx={{ width: '100%' }}>
+          {apiMessage?.message}
+        </Alert>
+      </Snackbar>
     </div>
   );
 
   /* A <Routes> looks through its children <Route>s and renders the first one that matches the current URL. */
   return (
-      <Routes>
-        <Route path="/login" element={<Login />}/>
-        <Route path={datasetsPath} element={PrivateRoute(Layout)}>
-          <Route path={cellsPath} element={Cells()} />
-          <Route path={equipmentPath} element={Equipment()} />
-          <Route path={harvestersPath} element={Harvesters()} />
-          <Route path={usersPath} element={ActivateUsers()} />
-          <Route path={profilePath} element={UserProfile()} />
-          <Route path={tokenPath} element={Tokens()} />
-          <Route index element={Datasets()} />
-        </Route>
-      </Routes>
+    <Routes>
+      <Route path="/login" element={<Login />}/>
+      <Route path={datasetsPath} element={PrivateRoute(Layout)}>
+        <Route path={cellsPath} element={Cells()} />
+        <Route path={equipmentPath} element={Equipment()} />
+        <Route path={harvestersPath} element={Harvesters()} />
+        <Route path={usersPath} element={ActivateUsers()} />
+        <Route path={profilePath} element={UserProfile()} />
+        <Route path={tokenPath} element={Tokens()} />
+        <Route index element={Datasets()} />
+      </Route>
+    </Routes>
   );
 }
  
diff --git a/frontend/src/UserProfile.tsx b/frontend/src/UserProfile.tsx
index 41c99102..376f4ec2 100644
--- a/frontend/src/UserProfile.tsx
+++ b/frontend/src/UserProfile.tsx
@@ -2,7 +2,7 @@ import React, {SyntheticEvent, useState} from 'react';
 import TextField from '@mui/material/TextField';
 import Paper from '@mui/material/Paper';
 import Container from '@mui/material/Container';
-import Connection from "./APIConnection";
+import Connection, {APIMessage} from "./APIConnection";
 import useStyles from "./UseStyles";
 import Typography from "@mui/material/Typography";
 import Stack from "@mui/material/Stack";
@@ -10,17 +10,12 @@ import Button from "@mui/material/Button";
 import Alert from "@mui/material/Alert";
 import Snackbar from "@mui/material/Snackbar";
 
-export type UpdateResult = {
-  success: boolean;
-  message: string;
-}
-
 export default function UserProfile() {
   const classes = useStyles();
   const [email, setEmail] = useState<string>(Connection.user?.email || '')
   const [password, setPassword] = useState<string>('')
   const [currentPassword, setCurrentPassword] = useState<string>('')
-  const [updateResult, setUpdateResult] = useState<UpdateResult|null>()
+  const [updateResult, setUpdateResult] = useState<APIMessage|null>()
   const [open, setOpen] = useState<boolean>(false)
 
   const updateUser = () => Connection.update_user(email, password, currentPassword)
@@ -91,7 +86,7 @@ export default function UserProfile() {
           </Button>
         </Stack>
         <Snackbar open={open} autoHideDuration={6000} onClose={handleClose}>
-          <Alert onClose={handleClose} severity={updateResult?.success? 'success' : 'error'} sx={{ width: '100%' }}>
+          <Alert onClose={handleClose} severity={updateResult?.severity} sx={{ width: '100%' }}>
             {updateResult?.message}
           </Alert>
         </Snackbar>