diff --git a/platform-independent/c/cli/src/mpw-cli.c b/platform-independent/c/cli/src/mpw-cli.c
index 4f1a946e..34daca53 100644
--- a/platform-independent/c/cli/src/mpw-cli.c
+++ b/platform-independent/c/cli/src/mpw-cli.c
@@ -714,7 +714,7 @@ void cli_mpw(Arguments *args, Operation *operation) {
     if (!operation->site)
         abort();
 
-    if (mpw_verbosity >= inf_level)
+    if (mpw_verbosity >= LogLevelInfo)
         fprintf( stderr, "%s's %s for %s:\n[ %s ]: ",
                 operation->file->user->fullName, operation->purposeResult, operation->site->siteName, operation->identicon );
 
diff --git a/platform-independent/c/core/build.gradle b/platform-independent/c/core/build.gradle
index 00c72dfb..99dc6ed5 100644
--- a/platform-independent/c/core/build.gradle
+++ b/platform-independent/c/core/build.gradle
@@ -31,12 +31,12 @@ library {
     toolChains {
         withType( VisualCpp ) {
             eachPlatform {
-                cppCompiler.withArguments { addAll( ['/TC', '/MT', '/Ox', '/DMPW_SODIUM=1', '/DSODIUM_STATIC', '/DSODIUM_EXPORT='] ) }
+                cppCompiler.withArguments { addAll( ['/TC', '/MT', '/Ox', '/DMPW_SODIUM=1', '/DSODIUM_STATIC', '/DSODIUM_EXPORT=', '/DMPW_LOG=mpw_log_app'] ) }
             }
         }
         withType( GccCompatibleToolChain ) {
             eachPlatform {
-                cppCompiler.withArguments { addAll( ['-x', 'c', '-O3', '-Werror', '-DMPW_SODIUM=1'] ) }
+                cppCompiler.withArguments { addAll( ['-x', 'c', '-O3', '-Werror', '-DMPW_SODIUM=1', '-DMPW_LOG=mpw_log_app'] ) }
             }
         }
     }
diff --git a/platform-independent/c/core/src/mpw-jni.c b/platform-independent/c/core/src/mpw-jni.c
index 05774d44..be812f20 100644
--- a/platform-independent/c/core/src/mpw-jni.c
+++ b/platform-independent/c/core/src/mpw-jni.c
@@ -7,11 +7,67 @@
 
 // TODO: We may need to zero the jbytes safely.
 
+static jobject logger;
+static JNIEnv *env;
+
+void mpw_log_app(LogLevel level, const char *format, ...) {
+    jmethodID method = NULL;
+    jclass class = (*env)->GetObjectClass( env, logger );
+    if (level >= LogLevelTrace)
+        method = (*env)->GetMethodID( env, class, "trace", "(Ljava/lang/String;)V" );
+    else if (level == LogLevelDebug)
+        method = (*env)->GetMethodID( env, class, "debug", "(Ljava/lang/String;)V" );
+    else if (level == LogLevelInfo)
+        method = (*env)->GetMethodID( env, class, "info", "(Ljava/lang/String;)V" );
+    else if (level == LogLevelWarning)
+        method = (*env)->GetMethodID( env, class, "warn", "(Ljava/lang/String;)V" );
+    else if (level <= LogLevelError)
+        method = (*env)->GetMethodID( env, class, "error", "(Ljava/lang/String;)V" );
+
+    va_list args;
+    va_start( args, format );
+
+    if (class && method && logger) {
+        char *message = NULL;
+        int length = vasprintf(&message, format, args);
+        if (length > 0)
+            (*env)->CallVoidMethod(env, logger, method, (*env)->NewStringUTF( env, message ));
+        if (message)
+            mpw_free(&message, (size_t) length);
+    }
+    else
+        // Can't log via slf4j, fall back to cli logger.
+        mpw_vlog_cli( level, format, args );
+
+    va_end( args );
+}
+
 JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void* reserved) {
-    JNIEnv* env;
     if ((*vm)->GetEnv( vm, (void **)&env, JNI_VERSION_1_6 ) != JNI_OK)
         return -1;
 
+    jclass class = (*env)->FindClass( env, "org/slf4j/LoggerFactory" );
+    jmethodID method = (*env)->GetStaticMethodID( env, class, "getLogger", "(Ljava/lang/String;)Lorg/slf4j/Logger;" );
+    jstring name = (*env)->NewStringUTF( env, "com.lyndir.masterpassword.algorithm" );
+    if (class && method && name)
+        logger = (*env)->CallStaticObjectMethod( env, class, method, name );
+    else
+        wrn( "Couldn't initialize JNI logger." );
+
+    class = (*env)->GetObjectClass( env, logger );
+    if ((*env)->CallBooleanMethod( env, logger, (*env)->GetMethodID( env, class, "isTraceEnabled", "()Z" ) ))
+        mpw_verbosity = LogLevelTrace;
+    else if ((*env)->CallBooleanMethod( env, logger, (*env)->GetMethodID( env, class, "isDebugEnabled", "()Z" ) ))
+        mpw_verbosity = LogLevelDebug;
+    else if ((*env)->CallBooleanMethod( env, logger, (*env)->GetMethodID( env, class, "isInfoEnabled", "()Z" ) ))
+        mpw_verbosity = LogLevelInfo;
+    else if ((*env)->CallBooleanMethod( env, logger, (*env)->GetMethodID( env, class, "isWarnEnabled", "()Z" ) ))
+        mpw_verbosity = LogLevelWarning;
+    else if ((*env)->CallBooleanMethod( env, logger, (*env)->GetMethodID( env, class, "isErrorEnabled", "()Z" ) ))
+        mpw_verbosity = LogLevelError;
+    else
+        mpw_verbosity = LogLevelFatal;
+
     return JNI_VERSION_1_6;
 }
 
diff --git a/platform-independent/c/core/src/mpw-util.c b/platform-independent/c/core/src/mpw-util.c
index f653838b..e63558e6 100644
--- a/platform-independent/c/core/src/mpw-util.c
+++ b/platform-independent/c/core/src/mpw-util.c
@@ -34,9 +34,53 @@ MP_LIBS_BEGIN
 #include "aes.h"
 MP_LIBS_END
 
-#ifdef inf_level
-int mpw_verbosity = inf_level;
-#endif
+int mpw_verbosity = LogLevelInfo;
+FILE *mpw_log_cli_file;
+
+void mpw_log_cli(LogLevel level, const char *format, ...) {
+    va_list args;
+    va_start( args, format );
+    mpw_vlog_cli( level, format, args );
+    va_end( args );
+}
+void mpw_vlog_cli(LogLevel level, const char *format, va_list args) {
+    if (!mpw_log_cli_file)
+        mpw_log_cli_file = stderr;
+
+    if (mpw_verbosity >= level) {
+        if (mpw_verbosity >= LogLevelDebug) {
+            switch (level) {
+                case LogLevelTrace:
+                    fprintf( mpw_log_cli_file, "[TRC] " );
+                    break;
+                case LogLevelDebug:
+                    fprintf( mpw_log_cli_file, "[DBG] " );
+                    break;
+                case LogLevelInfo:
+                    fprintf( mpw_log_cli_file, "[INF] " );
+                    break;
+                case LogLevelWarning:
+                    fprintf( mpw_log_cli_file, "[WRN] " );
+                    break;
+                case LogLevelError:
+                    fprintf( mpw_log_cli_file, "[ERR] " );
+                    break;
+                case LogLevelFatal:
+                    fprintf( mpw_log_cli_file, "[FTL] " );
+                    break;
+                default:
+                    fprintf( mpw_log_cli_file, "[???] " );
+                    break;
+            }
+        }
+
+        vfprintf( mpw_log_cli_file, format, args );
+        fprintf( mpw_log_cli_file, "\n" );
+    }
+
+    if (level <= LogLevelFatal)
+        abort();
+}
 
 void mpw_uint16(const uint16_t number, uint8_t buf[2]) {
 
diff --git a/platform-independent/c/core/src/mpw-util.h b/platform-independent/c/core/src/mpw-util.h
index ad3e0896..8d0e0487 100644
--- a/platform-independent/c/core/src/mpw-util.h
+++ b/platform-independent/c/core/src/mpw-util.h
@@ -27,48 +27,42 @@ MP_LIBS_BEGIN
 MP_LIBS_END
 
 //// Logging.
+typedef mpw_enum(int, LogLevel) {
+    /** Logging internal state. */
+    LogLevelTrace = 3,
+    /** Logging state and events interesting when investigating issues. */
+    LogLevelDebug = 2,
+    /** User messages. */
+    LogLevelInfo = 1,
+    /** Recoverable issues and user suggestions. */
+    LogLevelWarning = 0,
+    /** Unrecoverable issues. */
+    LogLevelError = -1,
+    /** Issues that lead to abortion. */
+    LogLevelFatal = -2,
+};
+LogLevel mpw_verbosity;
+
+/** mpw_log_cli is a sink that writes log messages to the mpw_log_cli_file, which defaults to stderr. */
+FILE *mpw_log_cli_file;
+void mpw_log_cli(LogLevel level, const char *format, ...);
+void mpw_vlog_cli(LogLevel level, const char *format, va_list args);
+
+/** mpw_log_app is a sink placeholder that an application can implement to consume log messages. */
+void mpw_log_app(LogLevel level, const char *format, ...);
+
+/** The sink you want to channel the log messages into, defaults to mpw_log_cli. */
+#ifndef MPW_LOG
+#define MPW_LOG mpw_log_cli
+#endif
+
 #ifndef trc
-extern int mpw_verbosity;
-
-#ifndef mpw_log_do
-#define mpw_log_do(level, format, ...) \
-    fprintf( stderr, format "\n", ##__VA_ARGS__ )
-#endif
-
-#ifndef mpw_log
-#define mpw_log(level, format, ...) do { \
-        if (mpw_verbosity >= level) { \
-            mpw_log_do( level, format, ##__VA_ARGS__ ); \
-        } \
-        if (level <= -2) { \
-            abort(); \
-        } \
-    } while (0)
-#endif
-
-/** Logging internal state. */
-#define trc_level 3
-#define trc(format, ...) mpw_log( trc_level, format, ##__VA_ARGS__ )
-
-/** Logging state and events interesting when investigating issues. */
-#define dbg_level 2
-#define dbg(format, ...) mpw_log( dbg_level, format, ##__VA_ARGS__ )
-
-/** User messages. */
-#define inf_level 1
-#define inf(format, ...) mpw_log( inf_level, format, ##__VA_ARGS__ )
-
-/** Recoverable issues and user suggestions. */
-#define wrn_level 0
-#define wrn(format, ...) mpw_log( wrn_level, format, ##__VA_ARGS__ )
-
-/** Unrecoverable issues. */
-#define err_level -1
-#define err(format, ...) mpw_log( err_level, format, ##__VA_ARGS__ )
-
-/** Issues that lead to abortion. */
-#define ftl_level -2
-#define ftl(format, ...) mpw_log( ftl_level, format, ##__VA_ARGS__ )
+#define trc(format, ...) MPW_LOG( LogLevelTrace, format, ##__VA_ARGS__ )
+#define dbg(format, ...) MPW_LOG( LogLevelDebug, format, ##__VA_ARGS__ )
+#define inf(format, ...) MPW_LOG( LogLevelInfo, format, ##__VA_ARGS__ )
+#define wrn(format, ...) MPW_LOG( LogLevelWarning, format, ##__VA_ARGS__ )
+#define err(format, ...) MPW_LOG( LogLevelError, format, ##__VA_ARGS__ )
+#define ftl(format, ...) MPW_LOG( LogLevelFatal, format, ##__VA_ARGS__ )
 #endif
 
 #ifndef min