diff --git a/README.md b/README.md
index 0613cb5..3d33ead 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,8 @@ running statistics, and export the result to CSV — no backend, no installation
 
 **<https://fyfar.github.io/multimeter-live/>**
 
-Open it in a Chromium-based browser, connect your meter, and click **Connect**.
+Open it in a supported browser (Chrome, Edge, Opera, or Firefox 151+), connect
+your meter, and click **Connect**.
 Everything runs locally in your browser — no data leaves your machine.
 
 ### Install & offline
@@ -56,8 +57,10 @@ update.
 ## Requirements
 
 - A **ZOYI ZT703s** multimeter connected over USB serial (see device note above).
-- A **Chromium-based browser** (Chrome, Edge, Opera). The Web Serial API is not
-  available in Firefox or Safari.
+- A browser with the **Web Serial API**: any **Chromium-based browser** (Chrome,
+  Edge, Opera) or **Firefox 151+** on desktop ([added May 2026](https://hacks.mozilla.org/2026/05/web-serial-support-in-firefox/)).
+  Safari is not supported. On Firefox Enterprise builds, Web Serial is disabled by default
+  and must be enabled via the `DefaultSerialGuardSetting` policy.
 - A served origin of **`https://` or `localhost`** — Web Serial requires a secure
   context. The live demo is served over HTTPS, so it works out of the box.
 
diff --git a/app/page.tsx b/app/page.tsx
index 7953843..34746ce 100644
--- a/app/page.tsx
+++ b/app/page.tsx
@@ -468,6 +468,7 @@ export default function Home() {
             stats={sessionStats}
             unit={chartUnit}
             decimals={statDecimals}
+            canRecord={status === 'connected'}
             onExportCsv={exportCsv}
             onToggleRecord={handleToggleRecord}
             onClear={flushSession}
diff --git a/components/DataLog.tsx b/components/DataLog.tsx
index eb668ba..bb1e391 100644
--- a/components/DataLog.tsx
+++ b/components/DataLog.tsx
@@ -1,7 +1,7 @@
 'use client';
 
 import { memo, useMemo, useState } from 'react';
-import { Search, Download, Pause, Play, Trash2 } from 'lucide-react';
+import { Search, Download, Square, Play, Trash2 } from 'lucide-react';
 import { clsx } from 'clsx';
 import { MODE_LABELS, type Reading } from '@/lib/parser';
 import { StatisticsPanel, type SessionStats } from '@/components/StatisticsPanel';
@@ -27,6 +27,7 @@ export function DataLog({
   stats,
   unit,
   decimals,
+  canRecord,
   onExportCsv,
   onToggleRecord,
   onClear,
@@ -38,6 +39,7 @@ export function DataLog({
   stats: SessionStats | null;
   unit: string;
   decimals?: number;
+  canRecord: boolean;
   onExportCsv: () => void;
   onToggleRecord: () => void;
   onClear: () => void;
@@ -179,9 +181,10 @@ export function DataLog({
             <div className="space-y-1.5">
               <ActionButton
                 onClick={onToggleRecord}
-                icon={recording ? <Pause size={12} /> : <Play size={12} />}
-                label={recording ? 'Pause Logging' : 'Resume Logging'}
-                variant={recording ? 'active' : 'default'}
+                icon={recording ? <Square size={12} /> : <Play size={12} />}
+                label={recording ? 'Stop Logging' : 'Start Logging'}
+                variant={recording ? 'danger' : 'success'}
+                disabled={!recording && !canRecord}
               />
               <ActionButton
                 onClick={onClear}
diff --git a/package.json b/package.json
index 301aceb..23056be 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "multimeter-live",
-  "version": "1.0.3",
+  "version": "1.0.4",
   "private": true,
   "description": "Real-time browser dashboard for the ZOYI ZT703s multimeter over the Web Serial API — live readings, trend chart, session stats, and CSV export. No backend.",
   "license": "MIT",