diff --git a/core/src/main/scala/com/evolutiongaming/catshelper/Log.scala b/core/src/main/scala/com/evolutiongaming/catshelper/Log.scala
index 0a354445..19d4477a 100644
--- a/core/src/main/scala/com/evolutiongaming/catshelper/Log.scala
+++ b/core/src/main/scala/com/evolutiongaming/catshelper/Log.scala
@@ -290,6 +290,8 @@ object Log {
 
     def prefixed(prefix: String): Log[F] = mapMsg(msg => s"$prefix $msg")
 
+    def withField(key: String, value: String): Log[F] = prefixed(s"$key=$value")
+
     def mapMdc(f: Log.Mdc => Log.Mdc): Log[F] = new Log[F] {
 
       def trace(msg: => String, mdc: Mdc): F[Unit] = self.trace(msg, f(mdc))
diff --git a/core/src/main/scala/com/evolutiongaming/catshelper/LogOf.scala b/core/src/main/scala/com/evolutiongaming/catshelper/LogOf.scala
index 43b7141d..2c789bef 100644
--- a/core/src/main/scala/com/evolutiongaming/catshelper/LogOf.scala
+++ b/core/src/main/scala/com/evolutiongaming/catshelper/LogOf.scala
@@ -92,5 +92,16 @@ object LogOf {
     }
 
     def forClass[C](implicit C: ClassTag[C]): F[Log[F]] = self.apply(C.runtimeClass)
+
+    def mapMsg(f: String => String)(implicit F: Monad[F]): LogOf[F] = new MapMsg(self, f)
+
+    def prefixed(prefix: String)(implicit F: Monad[F]): LogOf[F] = mapMsg(msg => s"$prefix $msg")
+
+    def withField(key: String, value: String)(implicit F: Monad[F]): LogOf[F] = prefixed(s"$key=$value")
   }
-}
\ No newline at end of file
+
+  private class MapMsg[F[_]: Monad](logOf: LogOf[F], mapper: String => String) extends LogOf[F] {
+    override def apply(source: String): F[Log[F]] = logOf.apply(source).map(_.mapMsg(mapper))
+    override def apply(source: Class[?]): F[Log[F]] = logOf.apply(source).map(_.mapMsg(mapper))
+  }
+}