diff --git a/client/stash.go b/client/stash.go
new file mode 100644
index 00000000..e8957b52
--- /dev/null
+++ b/client/stash.go
@@ -0,0 +1,303 @@
+// UNCHECKED
+
+package client
+
+import (
+	"bytes"
+	"encoding/binary"
+	"io"
+	"strings"
+)
+
+// Stash will store the data for the client, this will speed up booting
+// the QQ client but some data may not sync with the server. So it is
+// recommended to use this in development mode only.
+
+//go:generate stringer -type=syncMarker -trimprefix=syncMarker
+type syncMarker int8
+
+const (
+	syncMarkerNone syncMarker = iota
+	syncMarkerFriendList
+	syncMarkerFriendInfo
+	syncMarkerGroupList
+	syncMarkerGroupInfo
+	syncMarkerGroupMemberList
+	syncMarkerGroupMemberInfo
+)
+
+type StashSyncMarkerError struct {
+	marker   syncMarker
+	expected syncMarker
+}
+
+func (e *StashSyncMarkerError) Error() string {
+	return "stash sync marker error: expected " + e.expected.String() + ", got " + e.marker.String()
+}
+
+// WriteStash will write the stash to the given writer.
+func WriteStash(client *QQClient, writer io.Writer) {
+	var out intWriter
+	w := stashWriter{
+		stringIndex: make(map[string]uint64),
+	}
+
+	w.friendList(client.FriendList)
+	w.groupList(client.GroupList)
+
+	out.uvarint(uint64(w.strings.Len()))
+	out.uvarint(uint64(w.data.Len()))
+	_, _ = io.Copy(&out, &w.strings)
+	_, _ = io.Copy(&out, &w.data)
+	_, _ = io.Copy(writer, &out)
+}
+
+type stashWriter struct {
+	data        intWriter
+	strings     intWriter
+	stringIndex map[string]uint64
+}
+
+func (w *stashWriter) string(s string) {
+	off, ok := w.stringIndex[s]
+	if !ok {
+		off = uint64(w.strings.Len())
+		w.strings.uvarint(uint64(len(s)))
+		_, _ = w.strings.WriteString(s)
+		w.stringIndex[s] = off
+	}
+	w.uvarint(off)
+}
+
+func (w *stashWriter) sync(marker syncMarker) { w.data.uvarint(uint64(marker)) }
+func (w *stashWriter) uvarint(v uint64)       { w.data.uvarint(v) }
+func (w *stashWriter) svarint(v int64)        { w.data.svarint(v) }
+
+func (w *stashWriter) int64(v int64) {
+	var buf [8]byte
+	binary.LittleEndian.PutUint64(buf[:], uint64(v))
+	_, _ = w.data.Write(buf[:])
+}
+
+func (w *stashWriter) friendList(list []*FriendInfo) {
+	w.sync(syncMarkerFriendList)
+	w.uvarint(uint64(len(list)))
+	for _, friend := range list {
+		w.sync(syncMarkerFriendInfo)
+		w.int64(friend.Uin)
+		w.string(friend.Nickname)
+		w.string(friend.Remark)
+		w.svarint(int64(friend.FaceId))
+	}
+}
+
+func (w *stashWriter) groupList(list []*GroupInfo) {
+	w.sync(syncMarkerGroupList)
+	w.uvarint(uint64(len(list)))
+	for _, group := range list {
+		w.sync(syncMarkerGroupInfo)
+		w.int64(group.Uin)
+		w.int64(group.Code)
+		w.string(group.Name)
+		w.string(group.Memo)
+		w.int64(group.OwnerUin)
+		w.uvarint(uint64(group.GroupCreateTime))
+		w.uvarint(uint64(group.MemberCount))
+		w.uvarint(uint64(group.MaxMemberCount))
+		w.svarint(group.LastMsgSeq)
+
+		w.groupMemberList(group.Members)
+	}
+}
+
+func (w *stashWriter) groupMemberList(list []*GroupMemberInfo) {
+	w.sync(syncMarkerGroupMemberList)
+	w.uvarint(uint64(len(list)))
+	for _, member := range list {
+		w.sync(syncMarkerGroupMemberInfo)
+		w.int64(member.Uin)
+		w.uvarint(uint64(member.Gender))
+		w.string(member.Nickname)
+		w.string(member.CardName)
+		w.uvarint(uint64(member.Level))
+		w.int64(member.JoinTime)
+		w.int64(member.LastSpeakTime)
+		w.string(member.SpecialTitle)
+		w.svarint(member.SpecialTitleExpireTime)
+		w.svarint(member.ShutUpTimestamp)
+		w.uvarint(uint64(member.Permission))
+	}
+}
+
+type intWriter struct {
+	bytes.Buffer
+}
+
+func (w *intWriter) svarint(x int64) {
+	w.uvarint(uint64(x)<<1 ^ uint64(x>>63))
+}
+
+func (w *intWriter) uvarint(x uint64) {
+	var buf [binary.MaxVarintLen64]byte
+	n := binary.PutUvarint(buf[:], x)
+	_, _ = w.Write(buf[:n])
+}
+
+// ReadStash will read the stash from the given reader and apply to the given QQClient.
+func ReadStash(client *QQClient, data string) (err error) {
+	in := newIntReader(data)
+	sl := int64(in.uvarint())
+	dl := int64(in.uvarint())
+	whence, err := in.Seek(0, io.SeekCurrent)
+	if err != nil {
+		return err
+	}
+	sData := data[whence : whence+sl]
+	dData := data[whence+sl : whence+sl+dl]
+
+	r := stashReader{
+		data:        newIntReader(dData),
+		strings:     newIntReader(sData),
+		stringIndex: make(map[uint64]string),
+	}
+	defer func() {
+		if r := recover(); r != nil {
+			if e, ok := r.(error); ok {
+				err = e
+				return
+			}
+			panic(r)
+		}
+	}()
+
+	client.FriendList = r.friendList()
+	client.GroupList = r.groupList(client)
+	return nil
+}
+
+type stashReader struct {
+	data        intReader
+	strings     intReader
+	stringIndex map[uint64]string
+}
+
+func (r *stashReader) string() string {
+	off := r.data.uvarint()
+	if off == 0 {
+		return ""
+	}
+	if s, ok := r.stringIndex[off]; ok {
+		return s
+	}
+	_, _ = r.strings.Seek(int64(off), io.SeekStart)
+	l := int64(r.strings.uvarint())
+	whence, _ := r.strings.Seek(0, io.SeekCurrent)
+	s := r.strings.data[whence : whence+l]
+	r.stringIndex[off] = s
+	return s
+}
+
+func (r *stashReader) sync(marker syncMarker) {
+	got := syncMarker(r.data.uvarint())
+	if got != marker {
+		panic(&StashSyncMarkerError{
+			marker:   got,
+			expected: marker,
+		})
+	}
+}
+
+func (r *stashReader) friendList() []*FriendInfo {
+	r.sync(syncMarkerFriendList)
+	l := r.uvarint()
+	list := make([]*FriendInfo, l)
+	for i := uint64(0); i < l; i++ {
+		r.sync(syncMarkerFriendInfo)
+		list[i] = &FriendInfo{
+			Uin:      r.int64(),
+			Nickname: r.string(),
+			Remark:   r.string(),
+			FaceId:   int16(r.svarint()),
+		}
+	}
+	return list
+}
+
+func (r *stashReader) groupList(client *QQClient) []*GroupInfo {
+	r.sync(syncMarkerGroupList)
+	l := r.uvarint()
+	list := make([]*GroupInfo, l)
+	for i := uint64(0); i < l; i++ {
+		r.sync(syncMarkerGroupInfo)
+		list[i] = &GroupInfo{
+			Uin:             r.int64(),
+			Code:            r.int64(),
+			Name:            r.string(),
+			Memo:            r.string(),
+			OwnerUin:        r.int64(),
+			GroupCreateTime: uint32(r.uvarint()),
+			GroupLevel:      uint32(r.uvarint()),
+			MemberCount:     uint16(r.uvarint()),
+			MaxMemberCount:  uint16(r.uvarint()),
+			client:          client,
+		}
+		list[i].Members = r.groupMemberList(list[i])
+		list[i].LastMsgSeq = r.svarint()
+	}
+	return list
+}
+
+func (r *stashReader) groupMemberList(group *GroupInfo) []*GroupMemberInfo {
+	r.sync(syncMarkerGroupMemberList)
+	l := r.uvarint()
+	list := make([]*GroupMemberInfo, l)
+	for i := uint64(0); i < l; i++ {
+		r.sync(syncMarkerGroupMemberInfo)
+		list[i] = &GroupMemberInfo{
+			Group:                  group,
+			Uin:                    r.int64(),
+			Gender:                 byte(r.uvarint()),
+			Nickname:               r.string(),
+			CardName:               r.string(),
+			Level:                  uint16(r.uvarint()),
+			JoinTime:               r.int64(),
+			LastSpeakTime:          r.int64(),
+			SpecialTitle:           r.string(),
+			SpecialTitleExpireTime: r.svarint(),
+			ShutUpTimestamp:        r.svarint(),
+			Permission:             MemberPermission(r.uvarint()),
+		}
+	}
+	return list
+}
+
+func (r *stashReader) uvarint() uint64 { return r.data.uvarint() }
+func (r *stashReader) svarint() int64  { return r.data.svarint() }
+
+func (r *stashReader) int64() int64 {
+	var buf [8]byte
+	_, _ = r.data.Read(buf[:])
+	return int64(binary.LittleEndian.Uint64(buf[:]))
+}
+
+type intReader struct {
+	data string
+	*strings.Reader
+}
+
+func newIntReader(s string) intReader {
+	return intReader{
+		data:   s,
+		Reader: strings.NewReader(s),
+	}
+}
+
+func (r *intReader) svarint() int64 {
+	i, _ := binary.ReadVarint(r)
+	return i
+}
+
+func (r *intReader) uvarint() uint64 {
+	i, _ := binary.ReadUvarint(r)
+	return i
+}
diff --git a/client/syncmarker_string.go b/client/syncmarker_string.go
new file mode 100644
index 00000000..729efd8b
--- /dev/null
+++ b/client/syncmarker_string.go
@@ -0,0 +1,29 @@
+// Code generated by "stringer -type=syncMarker -trimprefix=syncMarker"; DO NOT EDIT.
+
+package client
+
+import "strconv"
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[syncMarkerNone-0]
+	_ = x[syncMarkerFriendList-1]
+	_ = x[syncMarkerFriendInfo-2]
+	_ = x[syncMarkerGroupList-3]
+	_ = x[syncMarkerGroupInfo-4]
+	_ = x[syncMarkerGroupMemberList-5]
+	_ = x[syncMarkerGroupMemberInfo-6]
+}
+
+const _syncMarker_name = "NoneFriendListFriendInfoGroupListGroupInfoGroupMemberListGroupMemberInfo"
+
+var _syncMarker_index = [...]uint8{0, 4, 14, 24, 33, 42, 57, 72}
+
+func (i syncMarker) String() string {
+	if i < 0 || i >= syncMarker(len(_syncMarker_index)-1) {
+		return "syncMarker(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+	return _syncMarker_name[_syncMarker_index[i]:_syncMarker_index[i+1]]
+}