diff --git a/.dockerignore b/.dockerignore
index 12e029c..48e2821 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -1,4 +1,8 @@
-.git
+# Keep just enough of .git for the build to read the current commit.
+.git/*
+!.git/HEAD
+!.git/refs
+!.git/packed-refs
 .claude
 node_modules
 .svelte-kit
diff --git a/src/app.d.ts b/src/app.d.ts
index be79b78..4b5ae00 100644
--- a/src/app.d.ts
+++ b/src/app.d.ts
@@ -1,6 +1,9 @@
 // See https://svelte.dev/docs/kit/types#app.d.ts
 declare global {
 	namespace App {}
+
+	/** Stamped in by vite.config.ts at build time. */
+	const __BUILD__: { version: string; commit: string; dirty: boolean; time: string };
 }
 
 export {};
diff --git a/src/lib/components/SettingsModal.svelte b/src/lib/components/SettingsModal.svelte
index c296b04..6b92676 100644
--- a/src/lib/components/SettingsModal.svelte
+++ b/src/lib/components/SettingsModal.svelte
@@ -8,6 +8,7 @@
 	type Tab = 'appearance' | 'input' | 'sync';
 	let tab = $state<Tab>('appearance');
 	const s = settings.data;
+	const build = __BUILD__;
 
 	let testing = $state(false);
 	let testResult = $state<{ ok: boolean; text: string } | null>(null);
@@ -55,6 +56,9 @@
 			<button class:active={tab === 'appearance'} onclick={() => (tab = 'appearance')}>Appearance</button>
 			<button class:active={tab === 'input'} onclick={() => (tab = 'input')}>Pen &amp; touch</button>
 			<button class:active={tab === 'sync'} onclick={() => (tab = 'sync')}>Sync</button>
+			<div class="build" title={`Commit ${build.commit}\nBuilt ${new Date(build.time).toLocaleString()}`}>
+				v{build.version} · {build.commit.slice(0, 7)}{build.dirty ? '-dirty' : ''}
+			</div>
 		</nav>
 		<section>
 			<button class="icon-btn close" title="Close" onclick={close}><XIcon size={18} /></button>
@@ -187,6 +191,14 @@
 		color: var(--faint);
 		padding: 0 10px 8px;
 	}
+	.build {
+		margin-top: auto;
+		padding: 0 10px;
+		font-family: var(--mono-font);
+		font-size: 11px;
+		color: var(--faint);
+		user-select: text;
+	}
 	nav button {
 		text-align: left;
 		border: 0;
diff --git a/vite.config.ts b/vite.config.ts
index 3f382a5..c94dbc9 100644
--- a/vite.config.ts
+++ b/vite.config.ts
@@ -1,8 +1,40 @@
+import { execSync } from 'node:child_process';
+import { existsSync, readFileSync } from 'node:fs';
 import { sveltekit } from '@sveltejs/kit/vite';
 import { defineConfig } from 'vitest/config';
 
+/** Current commit. Uses git when available, else reads .git directly (the Docker build has no git binary). */
+function gitCommit(): { commit: string; dirty: boolean } {
+	if (process.env.GIT_COMMIT) return { commit: process.env.GIT_COMMIT, dirty: false };
+	try {
+		const commit = execSync('git rev-parse HEAD', { stdio: ['ignore', 'pipe', 'ignore'] }).toString().trim();
+		const dirty = execSync('git status --porcelain --untracked-files=no', { stdio: ['ignore', 'pipe', 'ignore'] }).toString().trim() !== '';
+		return { commit, dirty };
+	} catch {
+		/* fall through */
+	}
+	try {
+		const head = readFileSync('.git/HEAD', 'utf8').trim();
+		if (!head.startsWith('ref: ')) return { commit: head, dirty: false };
+		const ref = head.slice(5);
+		if (existsSync(`.git/${ref}`)) return { commit: readFileSync(`.git/${ref}`, 'utf8').trim(), dirty: false };
+		const packed = readFileSync('.git/packed-refs', 'utf8').split('\n').find((l) => l.endsWith(` ${ref}`));
+		if (packed) return { commit: packed.split(' ')[0], dirty: false };
+	} catch {
+		/* no repository */
+	}
+	return { commit: 'unknown', dirty: false };
+}
+
+const build = {
+	version: JSON.parse(readFileSync('package.json', 'utf8')).version as string,
+	...gitCommit(),
+	time: new Date().toISOString()
+};
+
 export default defineConfig({
 	plugins: [sveltekit()],
+	define: { __BUILD__: JSON.stringify(build) },
 	test: {
 		include: ['src/**/*.test.ts'],
 		environment: 'node'