diff --git a/README.md b/README.md
index 0a3f8ad..bdad478 100644
--- a/README.md
+++ b/README.md
@@ -85,7 +85,7 @@ $ make install
 
 ####  1.1.1. <a name='requirements'></a>Requirements
 
-go 1.17 or higher.
+go 1.18 or higher.
 
 ###  1.2. <a name='download-binary'></a>Download binary
 
@@ -165,6 +165,7 @@ trdsql [options] SQL
 * `-ijson` JSON format for input.
 * `-iltsv` LTSV format for input.
 * `-itbln` TBLN format for input.
+* `-iwidth` width specification format for input.
 
 ####  3.2.1. <a name='input-options'></a>Input options
 
diff --git a/cmd/cmd.go b/cmd/cmd.go
index ffb7958..5d362d7 100644
--- a/cmd/cmd.go
+++ b/cmd/cmd.go
@@ -123,7 +123,7 @@ func (cli Cli) Run(args []string) int {
 	flags.BoolVar(&inFlag.LTSV, "iltsv", false, "LTSV format for input.")
 	flags.BoolVar(&inFlag.JSON, "ijson", false, "JSON format for input.")
 	flags.BoolVar(&inFlag.TBLN, "itbln", false, "TBLN format for input.")
-	flags.BoolVar(&inFlag.GW, "igw", false, "width specification format for input.")
+	flags.BoolVar(&inFlag.WIDTH, "iwidth", false, "width specification format for input.")
 
 	flags.StringVar(&outFile, "out", "", "output file name.")
 	flags.BoolVar(&outWithoutGuess, "out-without-guess", false, "output without guessing (when using -out).")
@@ -474,11 +474,11 @@ func quotedArg(arg string) string {
 
 // inputFlag represents the format of the input.
 type inputFlag struct {
-	CSV  bool
-	LTSV bool
-	JSON bool
-	TBLN bool
-	GW   bool
+	CSV   bool
+	LTSV  bool
+	JSON  bool
+	TBLN  bool
+	WIDTH bool
 }
 
 // inputFormat returns format from flag.
@@ -492,8 +492,8 @@ func inputFormat(i inputFlag) trdsql.Format {
 		return trdsql.JSON
 	case i.TBLN:
 		return trdsql.TBLN
-	case i.GW:
-		return trdsql.GW
+	case i.WIDTH:
+		return trdsql.WIDTH
 	default:
 		return trdsql.GUESS
 	}
@@ -501,7 +501,7 @@ func inputFormat(i inputFlag) trdsql.Format {
 
 func isInFormat(name string) bool {
 	switch name {
-	case "ig", "icsv", "iltsv", "ijson", "itbln", "igw":
+	case "ig", "icsv", "iltsv", "ijson", "itbln", "iwidth":
 		return true
 	}
 	return false
diff --git a/importer.go b/importer.go
index 18a02c2..0521a7d 100644
--- a/importer.go
+++ b/importer.go
@@ -317,8 +317,8 @@ func guessFormat(fileName string) Format {
 			return JSON
 		case "TBLN":
 			return TBLN
-		case "GW":
-			return GW
+		case "WIDTH":
+			return WIDTH
 		}
 		fileName = fileName[:len(fileName)-len(dotExt)]
 	}
diff --git a/input_gw_test.go b/input_gw_test.go
index d75d5e6..e5d5fad 100644
--- a/input_gw_test.go
+++ b/input_gw_test.go
@@ -55,10 +55,10 @@ func TestNewGWReader(t *testing.T) {
 				return
 			}
 			if !reflect.DeepEqual(got.names, tt.want.names) {
-				t.Errorf("NewLTSVReader().names = %v, want %v", got.names, tt.want.names)
+				t.Errorf("NewGWVReader().names = %v, want %v", got.names, tt.want.names)
 			}
 			if !reflect.DeepEqual(got.types, tt.want.types) {
-				t.Errorf("NewLTSVReader().types = %v, want %v", got.types, tt.want.types)
+				t.Errorf("NewGWReader().types = %v, want %v", got.types, tt.want.types)
 			}
 		})
 	}
diff --git a/reader.go b/reader.go
index 0bd41ff..080ebc4 100644
--- a/reader.go
+++ b/reader.go
@@ -172,7 +172,7 @@ func NewReader(reader io.Reader, readOpts *ReadOpts) (Reader, error) {
 		return NewJSONReader(reader, readOpts)
 	case TBLN:
 		return NewTBLNReader(reader, readOpts)
-	case GW:
+	case WIDTH:
 		return NewGWReader(reader, readOpts)
 	default:
 		return nil, ErrUnknownFormat
diff --git a/trdsql.go b/trdsql.go
index f1a1d41..c801c55 100644
--- a/trdsql.go
+++ b/trdsql.go
@@ -64,7 +64,7 @@ const (
 
 	// import
 	// Format using guesswidth library.
-	GW
+	WIDTH
 
 	// export
 	// Output as it is.
@@ -108,8 +108,8 @@ func (f Format) String() string {
 		return "JSON"
 	case TBLN:
 		return "TBLN"
-	case GW:
-		return "GW"
+	case WIDTH:
+		return "WIDTH"
 	case RAW:
 		return "RAW"
 	case MD: