diff --git a/app/src/main/java/de/krisenvorrat/app/data/repository/UpdateRepositoryImpl.kt b/app/src/main/java/de/krisenvorrat/app/data/repository/UpdateRepositoryImpl.kt
new file mode 100644
index 0000000..d5443d4
--- /dev/null
+++ b/app/src/main/java/de/krisenvorrat/app/data/repository/UpdateRepositoryImpl.kt
@@ -0,0 +1,88 @@
+package de.krisenvorrat.app.data.repository
+
+import de.krisenvorrat.app.domain.model.VersionInfo
+import de.krisenvorrat.app.domain.repository.UpdateRepository
+import io.ktor.client.HttpClient
+import io.ktor.client.call.body
+import io.ktor.client.request.get
+import io.ktor.client.request.prepareGet
+import io.ktor.client.statement.bodyAsChannel
+import io.ktor.http.HttpStatusCode
+import io.ktor.http.contentLength
+import io.ktor.utils.io.readAvailable
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import java.io.File
+import java.net.ConnectException
+import java.net.SocketTimeoutException
+import javax.inject.Inject
+
+internal class UpdateRepositoryImpl @Inject constructor(
+    private val httpClient: HttpClient
+) : UpdateRepository {
+
+    override suspend fun checkForUpdate(serverUrl: String): Result<VersionInfo> =
+        withContext(Dispatchers.IO) {
+            try {
+                val url = "${serverUrl.trimEnd('/')}/api/version"
+                val response = httpClient.get(url)
+                when (response.status) {
+                    HttpStatusCode.OK -> Result.success(response.body<VersionInfo>())
+                    else -> Result.failure(
+                        Exception("Server returned ${response.status.value}: ${response.status.description}")
+                    )
+                }
+            } catch (e: SocketTimeoutException) {
+                Result.failure(e)
+            } catch (e: ConnectException) {
+                Result.failure(e)
+            } catch (e: Exception) {
+                Result.failure(e)
+            }
+        }
+
+    override suspend fun downloadApk(
+        apkUrl: String,
+        targetFile: File,
+        onProgress: (Float) -> Unit
+    ): Result<File> = withContext(Dispatchers.IO) {
+        try {
+            targetFile.parentFile?.mkdirs()
+
+            httpClient.prepareGet(apkUrl).execute { response ->
+                if (response.status != HttpStatusCode.OK) {
+                    return@execute Result.failure(
+                        Exception("Download failed: ${response.status.value}")
+                    )
+                }
+
+                val totalBytes = response.contentLength() ?: -1L
+                val channel = response.bodyAsChannel()
+                val buffer = ByteArray(DOWNLOAD_BUFFER_SIZE)
+                var bytesRead = 0L
+
+                targetFile.outputStream().buffered().use { output ->
+                    while (!channel.isClosedForRead) {
+                        val read = channel.readAvailable(buffer)
+                        if (read <= 0) break
+                        output.write(buffer, 0, read)
+                        bytesRead += read
+                        if (totalBytes > 0) {
+                            onProgress(bytesRead.toFloat() / totalBytes.toFloat())
+                        }
+                    }
+                }
+
+                onProgress(1f)
+                Result.success(targetFile)
+            }
+        } catch (e: Exception) {
+            targetFile.delete()
+            Result.failure(e)
+        }
+    }
+
+    private companion object {
+        const val DOWNLOAD_BUFFER_SIZE = 8192
+    }
+}
diff --git a/app/src/main/java/de/krisenvorrat/app/di/RepositoryModule.kt b/app/src/main/java/de/krisenvorrat/app/di/RepositoryModule.kt
index 33c3c61..ed8aede 100644
--- a/app/src/main/java/de/krisenvorrat/app/di/RepositoryModule.kt
+++ b/app/src/main/java/de/krisenvorrat/app/di/RepositoryModule.kt
@@ -10,12 +10,14 @@ import de.krisenvorrat.app.data.repository.ItemRepositoryImpl
 import de.krisenvorrat.app.data.repository.LocationRepositoryImpl
 import de.krisenvorrat.app.data.repository.MessageRepositoryImpl
 import de.krisenvorrat.app.data.repository.SettingsRepositoryImpl
+import de.krisenvorrat.app.data.repository.UpdateRepositoryImpl
 import de.krisenvorrat.app.domain.repository.CategoryRepository
 import de.krisenvorrat.app.domain.repository.ImportExportRepository
 import de.krisenvorrat.app.domain.repository.ItemRepository
 import de.krisenvorrat.app.domain.repository.LocationRepository
 import de.krisenvorrat.app.domain.repository.MessageRepository
 import de.krisenvorrat.app.domain.repository.SettingsRepository
+import de.krisenvorrat.app.domain.repository.UpdateRepository
 import javax.inject.Singleton
 
 @Module
@@ -45,4 +47,8 @@ internal abstract class RepositoryModule {
     @Binds
     @Singleton
     abstract fun bindMessageRepository(impl: MessageRepositoryImpl): MessageRepository
+
+    @Binds
+    @Singleton
+    abstract fun bindUpdateRepository(impl: UpdateRepositoryImpl): UpdateRepository
 }
diff --git a/app/src/main/java/de/krisenvorrat/app/domain/model/UpdateCheckResult.kt b/app/src/main/java/de/krisenvorrat/app/domain/model/UpdateCheckResult.kt
new file mode 100644
index 0000000..bcb384f
--- /dev/null
+++ b/app/src/main/java/de/krisenvorrat/app/domain/model/UpdateCheckResult.kt
@@ -0,0 +1,8 @@
+package de.krisenvorrat.app.domain.model
+
+internal sealed interface UpdateCheckResult {
+    data class UpdateAvailable(val versionInfo: VersionInfo) : UpdateCheckResult
+    data object UpToDate : UpdateCheckResult
+    data class Error(val cause: Throwable) : UpdateCheckResult
+    data object NotConfigured : UpdateCheckResult
+}
diff --git a/app/src/main/java/de/krisenvorrat/app/domain/model/VersionInfo.kt b/app/src/main/java/de/krisenvorrat/app/domain/model/VersionInfo.kt
new file mode 100644
index 0000000..a22d41e
--- /dev/null
+++ b/app/src/main/java/de/krisenvorrat/app/domain/model/VersionInfo.kt
@@ -0,0 +1,10 @@
+package de.krisenvorrat.app.domain.model
+
+import kotlinx.serialization.Serializable
+
+@Serializable
+internal data class VersionInfo(
+    val versionCode: Int,
+    val versionName: String,
+    val apkUrl: String
+)
diff --git a/app/src/main/java/de/krisenvorrat/app/domain/repository/UpdateRepository.kt b/app/src/main/java/de/krisenvorrat/app/domain/repository/UpdateRepository.kt
new file mode 100644
index 0000000..9927c2f
--- /dev/null
+++ b/app/src/main/java/de/krisenvorrat/app/domain/repository/UpdateRepository.kt
@@ -0,0 +1,9 @@
+package de.krisenvorrat.app.domain.repository
+
+import de.krisenvorrat.app.domain.model.VersionInfo
+import java.io.File
+
+internal interface UpdateRepository {
+    suspend fun checkForUpdate(serverUrl: String): Result<VersionInfo>
+    suspend fun downloadApk(apkUrl: String, targetFile: File, onProgress: (Float) -> Unit): Result<File>
+}
diff --git a/app/src/main/java/de/krisenvorrat/app/domain/usecase/CheckForUpdateUseCase.kt b/app/src/main/java/de/krisenvorrat/app/domain/usecase/CheckForUpdateUseCase.kt
new file mode 100644
index 0000000..464b484
--- /dev/null
+++ b/app/src/main/java/de/krisenvorrat/app/domain/usecase/CheckForUpdateUseCase.kt
@@ -0,0 +1,33 @@
+package de.krisenvorrat.app.domain.usecase
+
+import de.krisenvorrat.app.domain.model.SettingsKey.StringKey
+import de.krisenvorrat.app.domain.model.UpdateCheckResult
+import de.krisenvorrat.app.domain.repository.SettingsRepository
+import de.krisenvorrat.app.domain.repository.UpdateRepository
+import javax.inject.Inject
+
+internal class CheckForUpdateUseCase @Inject constructor(
+    private val updateRepository: UpdateRepository,
+    private val settingsRepository: SettingsRepository
+) {
+
+    suspend operator fun invoke(currentVersionCode: Int): UpdateCheckResult {
+        val serverUrl = settingsRepository.getString(StringKey.ServerUrl)
+        if (serverUrl.isBlank()) {
+            return UpdateCheckResult.NotConfigured
+        }
+
+        return updateRepository.checkForUpdate(serverUrl).fold(
+            onSuccess = { versionInfo ->
+                if (versionInfo.versionCode > currentVersionCode) {
+                    UpdateCheckResult.UpdateAvailable(versionInfo)
+                } else {
+                    UpdateCheckResult.UpToDate
+                }
+            },
+            onFailure = { error ->
+                UpdateCheckResult.Error(error)
+            }
+        )
+    }
+}
diff --git a/app/src/test/java/de/krisenvorrat/app/data/repository/UpdateRepositoryImplTest.kt b/app/src/test/java/de/krisenvorrat/app/data/repository/UpdateRepositoryImplTest.kt
new file mode 100644
index 0000000..753c575
--- /dev/null
+++ b/app/src/test/java/de/krisenvorrat/app/data/repository/UpdateRepositoryImplTest.kt
@@ -0,0 +1,202 @@
+package de.krisenvorrat.app.data.repository
+
+import de.krisenvorrat.app.domain.model.VersionInfo
+import io.ktor.client.HttpClient
+import io.ktor.client.engine.mock.MockEngine
+import io.ktor.client.engine.mock.respond
+import io.ktor.client.engine.mock.respondError
+import io.ktor.client.plugins.contentnegotiation.ContentNegotiation
+import io.ktor.http.ContentType
+import io.ktor.http.HttpHeaders
+import io.ktor.http.HttpMethod
+import io.ktor.http.HttpStatusCode
+import io.ktor.http.headersOf
+import io.ktor.serialization.kotlinx.json.json
+import kotlinx.coroutines.test.runTest
+import kotlinx.serialization.json.Json
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import java.io.File
+
+class UpdateRepositoryImplTest {
+
+    private val jsonSerializer = Json {
+        ignoreUnknownKeys = true
+        encodeDefaults = true
+    }
+
+    private lateinit var httpClient: HttpClient
+    private lateinit var repository: UpdateRepositoryImpl
+
+    @After
+    fun tearDown() {
+        if (::httpClient.isInitialized) {
+            httpClient.close()
+        }
+    }
+
+    private fun createClient(engine: MockEngine): HttpClient = HttpClient(engine) {
+        install(ContentNegotiation) {
+            json(jsonSerializer)
+        }
+    }
+
+    // --- checkForUpdate ---
+
+    @Test
+    fun test_checkForUpdate_serverReturnsVersionInfo_returnsSuccess() = runTest {
+        // Given
+        val versionInfo = VersionInfo(versionCode = 5, versionName = "2.0", apkUrl = "https://example.com/app.apk")
+        val engine = MockEngine { request ->
+            assertEquals("/api/version", request.url.encodedPath)
+            assertEquals(HttpMethod.Get, request.method)
+            respond(
+                content = jsonSerializer.encodeToString(VersionInfo.serializer(), versionInfo),
+                status = HttpStatusCode.OK,
+                headers = headersOf(HttpHeaders.ContentType, ContentType.Application.Json.toString())
+            )
+        }
+        httpClient = createClient(engine)
+        repository = UpdateRepositoryImpl(httpClient)
+
+        // When
+        val result = repository.checkForUpdate("https://example.com")
+
+        // Then
+        assertTrue(result.isSuccess)
+        assertEquals(versionInfo, result.getOrNull())
+    }
+
+    @Test
+    fun test_checkForUpdate_serverReturns500_returnsFailure() = runTest {
+        // Given
+        val engine = MockEngine {
+            respondError(HttpStatusCode.InternalServerError)
+        }
+        httpClient = createClient(engine)
+        repository = UpdateRepositoryImpl(httpClient)
+
+        // When
+        val result = repository.checkForUpdate("https://example.com")
+
+        // Then
+        assertTrue(result.isFailure)
+        assertTrue(result.exceptionOrNull()?.message?.contains("500") == true)
+    }
+
+    @Test
+    fun test_checkForUpdate_serverUrlWithTrailingSlash_stripsSlash() = runTest {
+        // Given
+        val versionInfo = VersionInfo(versionCode = 5, versionName = "2.0", apkUrl = "https://example.com/app.apk")
+        val engine = MockEngine { request ->
+            assertEquals("/api/version", request.url.encodedPath)
+            respond(
+                content = jsonSerializer.encodeToString(VersionInfo.serializer(), versionInfo),
+                status = HttpStatusCode.OK,
+                headers = headersOf(HttpHeaders.ContentType, ContentType.Application.Json.toString())
+            )
+        }
+        httpClient = createClient(engine)
+        repository = UpdateRepositoryImpl(httpClient)
+
+        // When
+        val result = repository.checkForUpdate("https://example.com/")
+
+        // Then
+        assertTrue(result.isSuccess)
+    }
+
+    // --- downloadApk ---
+
+    @Test
+    fun test_downloadApk_serverReturnsData_writesFileAndReportsProgress() = runTest {
+        // Given
+        val apkData = ByteArray(1024) { it.toByte() }
+        val engine = MockEngine {
+            respond(
+                content = apkData,
+                status = HttpStatusCode.OK,
+                headers = headersOf(HttpHeaders.ContentLength, apkData.size.toString())
+            )
+        }
+        httpClient = createClient(engine)
+        repository = UpdateRepositoryImpl(httpClient)
+
+        val targetFile = File.createTempFile("test-apk", ".apk")
+        targetFile.deleteOnExit()
+        val progressValues = mutableListOf<Float>()
+
+        // When
+        val result = repository.downloadApk(
+            apkUrl = "https://example.com/app.apk",
+            targetFile = targetFile,
+            onProgress = { progressValues.add(it) }
+        )
+
+        // Then
+        assertTrue(result.isSuccess)
+        assertEquals(targetFile, result.getOrNull())
+        assertTrue(targetFile.exists())
+        assertEquals(apkData.size.toLong(), targetFile.length())
+        assertTrue(progressValues.isNotEmpty())
+        assertEquals(1f, progressValues.last(), 0.001f)
+    }
+
+    @Test
+    fun test_downloadApk_serverReturns404_returnsFailure() = runTest {
+        // Given
+        val engine = MockEngine {
+            respondError(HttpStatusCode.NotFound)
+        }
+        httpClient = createClient(engine)
+        repository = UpdateRepositoryImpl(httpClient)
+
+        val targetFile = File.createTempFile("test-apk", ".apk")
+        targetFile.deleteOnExit()
+
+        // When
+        val result = repository.downloadApk(
+            apkUrl = "https://example.com/app.apk",
+            targetFile = targetFile,
+            onProgress = {}
+        )
+
+        // Then
+        assertTrue(result.isFailure)
+    }
+
+    @Test
+    fun test_downloadApk_createsParentDirectories() = runTest {
+        // Given
+        val apkData = ByteArray(64) { it.toByte() }
+        val engine = MockEngine {
+            respond(
+                content = apkData,
+                status = HttpStatusCode.OK,
+                headers = headersOf(HttpHeaders.ContentLength, apkData.size.toString())
+            )
+        }
+        httpClient = createClient(engine)
+        repository = UpdateRepositoryImpl(httpClient)
+
+        val tempDir = File(System.getProperty("java.io.tmpdir"), "test-update-${System.nanoTime()}")
+        val targetFile = File(tempDir, "subdir/app-latest.apk")
+
+        try {
+            // When
+            val result = repository.downloadApk(
+                apkUrl = "https://example.com/app.apk",
+                targetFile = targetFile,
+                onProgress = {}
+            )
+
+            // Then
+            assertTrue(result.isSuccess)
+            assertTrue(targetFile.exists())
+        } finally {
+            tempDir.deleteRecursively()
+        }
+    }
+}
diff --git a/app/src/test/java/de/krisenvorrat/app/domain/usecase/CheckForUpdateUseCaseTest.kt b/app/src/test/java/de/krisenvorrat/app/domain/usecase/CheckForUpdateUseCaseTest.kt
new file mode 100644
index 0000000..44b1267
--- /dev/null
+++ b/app/src/test/java/de/krisenvorrat/app/domain/usecase/CheckForUpdateUseCaseTest.kt
@@ -0,0 +1,109 @@
+package de.krisenvorrat.app.domain.usecase
+
+import de.krisenvorrat.app.domain.model.SettingsKey.StringKey
+import de.krisenvorrat.app.domain.model.UpdateCheckResult
+import de.krisenvorrat.app.domain.model.VersionInfo
+import de.krisenvorrat.app.domain.repository.SettingsRepository
+import de.krisenvorrat.app.domain.repository.UpdateRepository
+import io.mockk.coEvery
+import io.mockk.coVerify
+import io.mockk.mockk
+import kotlinx.coroutines.test.runTest
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import java.net.ConnectException
+
+class CheckForUpdateUseCaseTest {
+
+    private val updateRepository: UpdateRepository = mockk()
+    private val settingsRepository: SettingsRepository = mockk()
+    private val useCase = CheckForUpdateUseCase(updateRepository, settingsRepository)
+
+    private fun setupServerUrl(url: String) {
+        coEvery { settingsRepository.getString(StringKey.ServerUrl) } returns url
+    }
+
+    @Test
+    fun test_invoke_serverHasNewerVersion_returnsUpdateAvailable() = runTest {
+        // Given
+        val versionInfo = VersionInfo(versionCode = 5, versionName = "2.0", apkUrl = "https://example.com/app.apk")
+        setupServerUrl("https://example.com")
+        coEvery { updateRepository.checkForUpdate("https://example.com") } returns Result.success(versionInfo)
+
+        // When
+        val result = useCase(currentVersionCode = 3)
+
+        // Then
+        assertTrue(result is UpdateCheckResult.UpdateAvailable)
+        assertEquals(versionInfo, (result as UpdateCheckResult.UpdateAvailable).versionInfo)
+    }
+
+    @Test
+    fun test_invoke_serverHasSameVersion_returnsUpToDate() = runTest {
+        // Given
+        val versionInfo = VersionInfo(versionCode = 3, versionName = "1.2", apkUrl = "https://example.com/app.apk")
+        setupServerUrl("https://example.com")
+        coEvery { updateRepository.checkForUpdate("https://example.com") } returns Result.success(versionInfo)
+
+        // When
+        val result = useCase(currentVersionCode = 3)
+
+        // Then
+        assertTrue(result is UpdateCheckResult.UpToDate)
+    }
+
+    @Test
+    fun test_invoke_serverHasOlderVersion_returnsUpToDate() = runTest {
+        // Given
+        val versionInfo = VersionInfo(versionCode = 2, versionName = "1.0", apkUrl = "https://example.com/app.apk")
+        setupServerUrl("https://example.com")
+        coEvery { updateRepository.checkForUpdate("https://example.com") } returns Result.success(versionInfo)
+
+        // When
+        val result = useCase(currentVersionCode = 3)
+
+        // Then
+        assertTrue(result is UpdateCheckResult.UpToDate)
+    }
+
+    @Test
+    fun test_invoke_serverUrlIsEmpty_returnsNotConfigured() = runTest {
+        // Given
+        setupServerUrl("")
+
+        // When
+        val result = useCase(currentVersionCode = 3)
+
+        // Then
+        assertTrue(result is UpdateCheckResult.NotConfigured)
+        coVerify(exactly = 0) { updateRepository.checkForUpdate(any()) }
+    }
+
+    @Test
+    fun test_invoke_serverUrlIsBlank_returnsNotConfigured() = runTest {
+        // Given
+        setupServerUrl("   ")
+
+        // When
+        val result = useCase(currentVersionCode = 3)
+
+        // Then
+        assertTrue(result is UpdateCheckResult.NotConfigured)
+    }
+
+    @Test
+    fun test_invoke_networkError_returnsError() = runTest {
+        // Given
+        setupServerUrl("https://example.com")
+        val networkError = ConnectException("Connection refused")
+        coEvery { updateRepository.checkForUpdate("https://example.com") } returns Result.failure(networkError)
+
+        // When
+        val result = useCase(currentVersionCode = 3)
+
+        // Then
+        assertTrue(result is UpdateCheckResult.Error)
+        assertEquals(networkError, (result as UpdateCheckResult.Error).cause)
+    }
+}