diff --git a/bitlogger/file_backend_native.mbt b/bitlogger/file_backend_native.mbt
index f9245e5..472536c 100644
--- a/bitlogger/file_backend_native.mbt
+++ b/bitlogger/file_backend_native.mbt
@@ -32,28 +32,28 @@ fn string_to_c_bytes(str : String) -> Bytes {
 }
 
 #external
-priv type NativeFileHandle
+type NativeFileHandle
 
 #borrow(path, mode)
-extern "c" fn file_open_ffi(path : Bytes, mode : Bytes) -> NativeFileHandle = "fopen"
+extern "C" fn file_open_ffi(path : Bytes, mode : Bytes) -> NativeFileHandle = "fopen"
 
-extern "c" fn file_is_null_ffi(handle : NativeFileHandle) -> Bool = "%null?"
+extern "C" fn file_is_null_ffi(handle : NativeFileHandle) -> Bool = "moonbitlang_async_pointer_is_null"
 
 #borrow(buffer)
-extern "c" fn file_write_ffi(
+extern "C" fn file_write_ffi(
   buffer : Bytes,
   size : Int,
   count : Int,
   handle : NativeFileHandle,
 ) -> Int = "fwrite"
 
-extern "c" fn file_flush_ffi(handle : NativeFileHandle) -> Int = "fflush"
+extern "C" fn file_flush_ffi(handle : NativeFileHandle) -> Int = "fflush"
 
-extern "c" fn file_close_ffi(handle : NativeFileHandle) -> Int = "fclose"
+extern "C" fn file_close_ffi(handle : NativeFileHandle) -> Int = "fclose"
 
 pub struct FileHandle {
-  raw : NativeFileHandle
   path : String
+  raw : NativeFileHandle
 }
 
 fn open_file_handle_internal(path : String, append : Bool) -> FileHandle? {
diff --git a/bitlogger/record.mbt b/bitlogger/record.mbt
index ebe44d1..027b37e 100644
--- a/bitlogger/record.mbt
+++ b/bitlogger/record.mbt
@@ -15,7 +15,7 @@ pub struct Record {
   fields : Array[Field]
 }
 
-fn record(
+pub fn Record::new(
   level : Level,
   message : String,
   timestamp_ms~ : UInt64 = 0UL,
@@ -24,3 +24,13 @@ fn record(
 ) -> Record {
   { level, timestamp_ms, target, message, fields }
 }
+
+fn record(
+  level : Level,
+  message : String,
+  timestamp_ms~ : UInt64 = 0UL,
+  target~ : String = "",
+  fields~ : Array[Field] = [],
+) -> Record {
+  Record::new(level, message, timestamp_ms=timestamp_ms, target=target, fields=fields)
+}
diff --git a/bitlogger_async/async_logger_native.mbt b/bitlogger_async/async_logger_native.mbt
new file mode 100644
index 0000000..eac2a87
--- /dev/null
+++ b/bitlogger_async/async_logger_native.mbt
@@ -0,0 +1,260 @@
+pub(all) suberror AsyncLoggerClosed {
+  AsyncLoggerClosed
+}
+
+pub(all) enum AsyncOverflowPolicy {
+  Blocking
+  DropOldest
+  DropNewest
+}
+
+pub struct AsyncLoggerConfig {
+  max_pending : Int
+  overflow : AsyncOverflowPolicy
+}
+
+pub fn AsyncLoggerConfig::new(
+  max_pending~ : Int = 0,
+  overflow~ : AsyncOverflowPolicy = AsyncOverflowPolicy::Blocking,
+) -> AsyncLoggerConfig {
+  { max_pending, overflow }
+}
+
+pub struct AsyncLogger[S] {
+  min_level : @bitlogger.Level
+  target : String
+  timestamp : Bool
+  overflow : AsyncOverflowPolicy
+  sink : S
+  context_fields : Array[@bitlogger.Field]
+  filter : (@bitlogger.Record) -> Bool
+  patch : @bitlogger.RecordPatch
+  queue : @async.Queue[@bitlogger.Record]
+  pending_count : Ref[Int]
+  dropped_count : Ref[Int]
+}
+
+pub fn[S] async_logger(
+  sink : S,
+  config~ : AsyncLoggerConfig = AsyncLoggerConfig::new(),
+  min_level~ : @bitlogger.Level = @bitlogger.Level::Info,
+  target~ : String = "",
+) -> AsyncLogger[S] {
+  {
+    min_level,
+    target,
+    timestamp: false,
+    overflow: config.overflow,
+    sink,
+    context_fields: [],
+    filter: fn(_) { true },
+    patch: @bitlogger.identity_patch(),
+    queue: @async.Queue::new(kind=queue_kind_of(config)),
+    pending_count: Ref::new(0),
+    dropped_count: Ref::new(0),
+  }
+}
+
+fn queue_kind_of(config : AsyncLoggerConfig) -> @aqueue.Kind {
+  let limit = if config.max_pending < 0 { 0 } else { config.max_pending }
+  match config.overflow {
+    AsyncOverflowPolicy::Blocking => @aqueue.Kind::Blocking(limit)
+    AsyncOverflowPolicy::DropOldest => @aqueue.Kind::DiscardOldest(limit)
+    AsyncOverflowPolicy::DropNewest => @aqueue.Kind::DiscardLatest(limit)
+  }
+}
+
+pub fn[S] AsyncLogger::with_timestamp(self : AsyncLogger[S], enabled~ : Bool = true) -> AsyncLogger[S] {
+  { ..self, timestamp: enabled }
+}
+
+pub fn[S] AsyncLogger::with_target(self : AsyncLogger[S], target : String) -> AsyncLogger[S] {
+  { ..self, target }
+}
+
+pub fn[S] AsyncLogger::with_context_fields(
+  self : AsyncLogger[S],
+  fields : Array[@bitlogger.Field],
+) -> AsyncLogger[S] {
+  { ..self, context_fields: fields }
+}
+
+pub fn[S] AsyncLogger::with_filter(
+  self : AsyncLogger[S],
+  predicate : (@bitlogger.Record) -> Bool,
+) -> AsyncLogger[S] {
+  let current = self.filter
+  {
+    ..self,
+    filter: fn(rec) {
+      current(rec) && predicate(rec)
+    },
+  }
+}
+
+pub fn[S] AsyncLogger::with_patch(
+  self : AsyncLogger[S],
+  patch : @bitlogger.RecordPatch,
+) -> AsyncLogger[S] {
+  let current = self.patch
+  {
+    ..self,
+    patch: fn(rec) {
+      patch(current(rec))
+    },
+  }
+}
+
+pub fn[S] AsyncLogger::with_min_level(
+  self : AsyncLogger[S],
+  min_level : @bitlogger.Level,
+) -> AsyncLogger[S] {
+  { ..self, min_level }
+}
+
+fn combine_targets(parent : String, child : String) -> String {
+  if parent == "" {
+    child
+  } else if child == "" {
+    parent
+  } else {
+    "\{parent}.\{child}"
+  }
+}
+
+pub fn[S] AsyncLogger::child(self : AsyncLogger[S], target : String) -> AsyncLogger[S] {
+  { ..self, target: combine_targets(self.target, target) }
+}
+
+pub fn[S] AsyncLogger::is_enabled(self : AsyncLogger[S], level : @bitlogger.Level) -> Bool {
+  level.enabled(self.min_level)
+}
+
+pub async fn[S] AsyncLogger::log(
+  self : AsyncLogger[S],
+  level : @bitlogger.Level,
+  message : String,
+  fields~ : Array[@bitlogger.Field] = [],
+  target? : String = "",
+) -> Unit {
+  guard self.is_enabled(level) else {
+    ()
+  }
+  let actual_target = if target == "" { self.target } else { target }
+  let timestamp_ms = if self.timestamp { @env.now() } else { 0UL }
+  let rec = @bitlogger.Record::new(
+    level,
+    message,
+    timestamp_ms=timestamp_ms,
+    target=actual_target,
+    fields=merge_fields(self.context_fields, fields),
+  )
+  let rec = (self.patch)(rec)
+  guard (self.filter)(rec) else {
+    ()
+  }
+  let accepted = self.queue.try_put(rec) catch {
+    err if err is AsyncLoggerClosed => false
+    err => raise err
+  }
+  if accepted {
+    self.pending_count.val += 1
+  } else {
+    match self.overflow {
+      AsyncOverflowPolicy::Blocking => {
+        self.queue.put(rec) catch {
+          err if err is AsyncLoggerClosed => ()
+          err => raise err
+        }
+        self.pending_count.val += 1
+      }
+      AsyncOverflowPolicy::DropOldest | AsyncOverflowPolicy::DropNewest => {
+        self.dropped_count.val += 1
+      }
+    }
+  }
+}
+
+fn merge_fields(
+  left : Array[@bitlogger.Field],
+  right : Array[@bitlogger.Field],
+) -> Array[@bitlogger.Field] {
+  if left.length() == 0 {
+    right
+  } else if right.length() == 0 {
+    left
+  } else {
+    left + right
+  }
+}
+
+pub async fn[S] AsyncLogger::trace(
+  self : AsyncLogger[S],
+  message : String,
+  fields~ : Array[@bitlogger.Field] = [],
+) -> Unit {
+  self.log(@bitlogger.Level::Trace, message, fields=fields)
+}
+
+pub async fn[S] AsyncLogger::debug(
+  self : AsyncLogger[S],
+  message : String,
+  fields~ : Array[@bitlogger.Field] = [],
+) -> Unit {
+  self.log(@bitlogger.Level::Debug, message, fields=fields)
+}
+
+pub async fn[S] AsyncLogger::info(
+  self : AsyncLogger[S],
+  message : String,
+  fields~ : Array[@bitlogger.Field] = [],
+) -> Unit {
+  self.log(@bitlogger.Level::Info, message, fields=fields)
+}
+
+pub async fn[S] AsyncLogger::warn(
+  self : AsyncLogger[S],
+  message : String,
+  fields~ : Array[@bitlogger.Field] = [],
+) -> Unit {
+  self.log(@bitlogger.Level::Warn, message, fields=fields)
+}
+
+pub async fn[S] AsyncLogger::error(
+  self : AsyncLogger[S],
+  message : String,
+  fields~ : Array[@bitlogger.Field] = [],
+) -> Unit {
+  self.log(@bitlogger.Level::Error, message, fields=fields)
+}
+
+pub fn[S] AsyncLogger::pending_count(self : AsyncLogger[S]) -> Int {
+  self.pending_count.val
+}
+
+pub fn[S] AsyncLogger::dropped_count(self : AsyncLogger[S]) -> Int {
+  self.dropped_count.val
+}
+
+pub fn[S] AsyncLogger::close(self : AsyncLogger[S], clear? : Bool = false) -> Unit {
+  self.queue.close(error=AsyncLoggerClosed, clear=clear)
+}
+
+pub async fn[S] AsyncLogger::wait_idle(self : AsyncLogger[S]) -> Unit {
+  while self.pending_count() > 0 {
+    @async.pause()
+  }
+}
+
+pub async fn[S : @bitlogger.Sink] AsyncLogger::run(self : AsyncLogger[S]) -> Unit {
+  while true {
+    let rec = self.queue.get() catch {
+      err if err is AsyncLoggerClosed => break
+      err => raise err
+    }
+    self.sink.write(rec)
+    if self.pending_count.val > 0 {
+      self.pending_count.val -= 1
+    }
+  }
+}
diff --git a/bitlogger_async/async_logger_stub.mbt b/bitlogger_async/async_logger_stub.mbt
new file mode 100644
index 0000000..19fc113
--- /dev/null
+++ b/bitlogger_async/async_logger_stub.mbt
@@ -0,0 +1,36 @@
+pub(all) suberror AsyncLoggerClosed {
+  AsyncLoggerClosed
+}
+
+pub(all) enum AsyncOverflowPolicy {
+  Blocking
+  DropOldest
+  DropNewest
+}
+
+pub struct AsyncLoggerConfig {
+  max_pending : Int
+  overflow : AsyncOverflowPolicy
+}
+
+pub fn AsyncLoggerConfig::new(
+  max_pending~ : Int = 0,
+  overflow~ : AsyncOverflowPolicy = AsyncOverflowPolicy::Blocking,
+) -> AsyncLoggerConfig {
+  { max_pending, overflow }
+}
+
+pub struct AsyncLogger[S] {}
+
+pub fn async_logger[S : @bitlogger.Sink](
+  sink : S,
+  config~ : AsyncLoggerConfig = AsyncLoggerConfig::new(),
+  min_level~ : @bitlogger.Level = @bitlogger.Level::Info,
+  target~ : String = "",
+) -> AsyncLogger[S] {
+  ignore(sink)
+  ignore(config)
+  ignore(min_level)
+  ignore(target)
+  abort("bitlogger_async currently only supports native/llvm backends")
+}
diff --git a/bitlogger_async/moon.pkg b/bitlogger_async/moon.pkg
new file mode 100644
index 0000000..daafd9f
--- /dev/null
+++ b/bitlogger_async/moon.pkg
@@ -0,0 +1,16 @@
+import {
+  "Nanaloveyuki/BitLogger/bitlogger" @bitlogger,
+  "moonbitlang/async" @async,
+  "moonbitlang/async/aqueue" @aqueue,
+  "moonbitlang/core/env" @env,
+  "moonbitlang/core/ref",
+}
+
+supported_targets = "+native"
+
+options(
+  targets: {
+    "async_logger_native.mbt": [ "native", "llvm" ],
+    "async_logger_stub.mbt": [ "js", "wasm", "wasm-gc" ],
+  },
+)
diff --git a/examples/async_basic/main.mbt b/examples/async_basic/main.mbt
new file mode 100644
index 0000000..23a1942
--- /dev/null
+++ b/examples/async_basic/main.mbt
@@ -0,0 +1,27 @@
+async fn main {
+  let logger = @lib_async.async_logger(
+    @lib.text_console_sink(@lib.text_formatter(show_timestamp=false, separator=" | ")),
+    config=@lib_async.AsyncLoggerConfig::new(
+      max_pending=2,
+      overflow=@lib_async.AsyncOverflowPolicy::DropOldest,
+    ),
+    min_level=@lib.Level::Info,
+    target="async.demo",
+  )
+    .with_timestamp()
+    .with_context_fields([@lib.field("service", "bitlogger")])
+    .with_filter(@lib.target_has_prefix("async"))
+    .with_patch(@lib.compose_patches([
+      @lib.prefix_message("[async] "),
+      @lib.redact_fields(["token"]),
+    ]))
+
+  @async.with_task_group(group => {
+    group.spawn_bg(allow_failure=true, () => logger.run())
+    logger.info("one", fields=[@lib.field("token", "secret")])
+    logger.child("worker").info("two")
+    logger.with_target("skip.demo").info("three")
+    logger.wait_idle()
+    logger.close()
+  })
+}
diff --git a/examples/async_basic/moon.pkg b/examples/async_basic/moon.pkg
new file mode 100644
index 0000000..f67357c
--- /dev/null
+++ b/examples/async_basic/moon.pkg
@@ -0,0 +1,11 @@
+import {
+  "Nanaloveyuki/BitLogger/bitlogger" @lib,
+  "Nanaloveyuki/BitLogger/bitlogger_async" @lib_async,
+  "moonbitlang/async" @async,
+}
+
+supported_targets = "+native"
+
+options(
+  is_main: true,
+)
diff --git a/moon.mod.json b/moon.mod.json
index 4599e91..5769993 100644
--- a/moon.mod.json
+++ b/moon.mod.json
@@ -2,7 +2,8 @@
   "name": "Nanaloveyuki/BitLogger",
   "version": "0.2.0",
   "deps": {
-    "maria/json_parser": "0.1.1"
+    "maria/json_parser": "0.1.1",
+    "moonbitlang/async": "0.18.1"
   },
   "readme": "README.mbt.md",
   "repository": "https://github.com/Nanaloveyuki/BitLogger",
@@ -13,4 +14,4 @@
     "moonbit"
   ],
   "description": "A structured logger for MoonBit."
-}
+}
\ No newline at end of file