diff --git a/ascii.go b/ascii.go
new file mode 100644
index 0000000..6c66eb5
--- /dev/null
+++ b/ascii.go
@@ -0,0 +1,124 @@
+package jsoncolor
+
+import "unsafe"
+
+// asciiValid returns true if b contains only ASCII characters.
+//
+// From https://github.com/segmentio/encoding/blob/v0.1.14/ascii/valid.go#L28
+//
+//go:nosplit
+func asciiValid(b []byte) bool {
+	s, n := unsafe.Pointer(&b), uintptr(len(b))
+
+	i := uintptr(0)
+	p := *(*unsafe.Pointer)(s)
+
+	for n >= 8 {
+		if ((*(*uint64)(unsafe.Pointer(uintptr(p) + i))) & 0x8080808080808080) != 0 {
+			return false
+		}
+		i += 8
+		n -= 8
+	}
+
+	if n >= 4 {
+		if ((*(*uint32)(unsafe.Pointer(uintptr(p) + i))) & 0x80808080) != 0 {
+			return false
+		}
+		i += 4
+		n -= 4
+	}
+
+	var x uint32
+	switch n {
+	case 3:
+		x = uint32(*(*uint8)(unsafe.Pointer(uintptr(p) + i))) | uint32(*(*uint16)(unsafe.Pointer(uintptr(p) + i + 1)))<<8
+	case 2:
+		x = uint32(*(*uint16)(unsafe.Pointer(uintptr(p) + i)))
+	case 1:
+		x = uint32(*(*uint8)(unsafe.Pointer(uintptr(p) + i)))
+	default:
+		return true
+	}
+	return (x & 0x80808080) == 0
+}
+
+// asciiValidPrint returns true if b contains only printable ASCII characters.
+//
+// From https://github.com/segmentio/encoding/blob/v0.1.14/ascii/valid.go#L83
+//
+//go:nosplit
+func asciiValidPrint(b []byte) bool {
+	s, n := unsafe.Pointer(&b), uintptr(len(b))
+
+	if n == 0 {
+		return true
+	}
+
+	i := uintptr(0)
+	p := *(*unsafe.Pointer)(s)
+
+	for (n - i) >= 8 {
+		x := *(*uint64)(unsafe.Pointer(uintptr(p) + i))
+		if hasLess64(x, 0x20) || hasMore64(x, 0x7e) {
+			return false
+		}
+		i += 8
+	}
+
+	if (n - i) >= 4 {
+		x := *(*uint32)(unsafe.Pointer(uintptr(p) + i))
+		if hasLess32(x, 0x20) || hasMore32(x, 0x7e) {
+			return false
+		}
+		i += 4
+	}
+
+	var x uint32
+	switch n - i {
+	case 3:
+		x = 0x20000000 | uint32(*(*uint8)(unsafe.Pointer(uintptr(p) + i))) | uint32(*(*uint16)(unsafe.Pointer(uintptr(p) + i + 1)))<<8
+	case 2:
+		x = 0x20200000 | uint32(*(*uint16)(unsafe.Pointer(uintptr(p) + i)))
+	case 1:
+		x = 0x20202000 | uint32(*(*uint8)(unsafe.Pointer(uintptr(p) + i)))
+	default:
+		return true
+	}
+	return !(hasLess32(x, 0x20) || hasMore32(x, 0x7e))
+}
+
+// https://graphics.stanford.edu/~seander/bithacks.html#HasLessInWord
+const (
+	hasLessConstL64 = (^uint64(0)) / 255
+	hasLessConstR64 = hasLessConstL64 * 128
+
+	hasLessConstL32 = (^uint32(0)) / 255
+	hasLessConstR32 = hasLessConstL32 * 128
+
+	hasMoreConstL64 = (^uint64(0)) / 255
+	hasMoreConstR64 = hasMoreConstL64 * 128
+
+	hasMoreConstL32 = (^uint32(0)) / 255
+	hasMoreConstR32 = hasMoreConstL32 * 128
+)
+
+//go:nosplit
+func hasLess64(x, n uint64) bool {
+	return ((x - (hasLessConstL64 * n)) & ^x & hasLessConstR64) != 0
+}
+
+//go:nosplit
+func hasLess32(x, n uint32) bool {
+	return ((x - (hasLessConstL32 * n)) & ^x & hasLessConstR32) != 0
+}
+
+//go:nosplit
+func hasMore64(x, n uint64) bool {
+	return (((x + (hasMoreConstL64 * (127 - n))) | x) & hasMoreConstR64) != 0
+}
+
+//go:nosplit
+func hasMore32(x, n uint32) bool {
+	return (((x + (hasMoreConstL32 * (127 - n))) | x) & hasMoreConstR32) != 0
+}
diff --git a/ascii_test.go b/ascii_test.go
new file mode 100644
index 0000000..9f9d306
--- /dev/null
+++ b/ascii_test.go
@@ -0,0 +1,65 @@
+package jsoncolor
+
+import (
+	"strings"
+	"testing"
+)
+
+// Based on https://github.com/segmentio/encoding/blob/v0.1.14/ascii/valid_test.go
+var testCases = [...]struct {
+	valid      bool
+	validPrint bool
+	str        string
+}{
+	{valid: true, validPrint: true, str: ""},
+	{valid: true, validPrint: true, str: "hello"},
+	{valid: true, validPrint: true, str: "Hello World!"},
+	{valid: true, validPrint: true, str: "Hello\"World!"},
+	{valid: true, validPrint: true, str: "Hello\\World!"},
+	{valid: true, validPrint: false, str: "Hello\nWorld!"},
+	{valid: true, validPrint: false, str: "Hello\rWorld!"},
+	{valid: true, validPrint: false, str: "Hello\tWorld!"},
+	{valid: true, validPrint: false, str: "Hello\bWorld!"},
+	{valid: true, validPrint: false, str: "Hello\fWorld!"},
+	{valid: true, validPrint: true, str: "H~llo World!"},
+	{valid: true, validPrint: true, str: "H~llo"},
+	{valid: false, validPrint: false, str: "你好"},
+	{valid: true, validPrint: true, str: "~"},
+	{valid: false, validPrint: false, str: "\x80"},
+	{valid: true, validPrint: false, str: "\x7F"},
+	{valid: false, validPrint: false, str: "\xFF"},
+	{valid: true, validPrint: true, str: "some kind of long string with only ascii characters."},
+	{valid: false, validPrint: false, str: "some kind of long string with a non-ascii character at the end.\xff"},
+	{valid: true, validPrint: true, str: strings.Repeat("1234567890", 1000)},
+}
+
+func TestAsciiValid(t *testing.T) {
+	for _, tc := range testCases {
+		t.Run(limit(tc.str), func(t *testing.T) {
+			expect := tc.validPrint
+
+			if valid := asciiValidPrint([]byte(tc.str)); expect != valid {
+				t.Errorf("expected %t but got %t", expect, valid)
+			}
+		})
+	}
+}
+
+func TestAsciiValidPrint(t *testing.T) {
+	for _, tc := range testCases {
+		t.Run(limit(tc.str), func(t *testing.T) {
+			expect := tc.validPrint
+
+			if valid := asciiValidPrint([]byte(tc.str)); expect != valid {
+				t.Errorf("expected %t but got %t", expect, valid)
+			}
+		})
+	}
+}
+
+func limit(s string) string {
+	if len(s) > 17 {
+		return s[:17] + "..."
+	}
+	return s
+}
diff --git a/go.mod b/go.mod
index 985ced6..5099b58 100644
--- a/go.mod
+++ b/go.mod
@@ -8,11 +8,10 @@ require (
 	github.com/kr/pretty v0.2.1 // indirect
 	github.com/kr/text v0.2.0 // indirect
 	github.com/mattn/go-colorable v0.1.8
-	github.com/mattn/go-isatty v0.0.14
+	github.com/mattn/go-isatty v0.0.20
 	github.com/nwidger/jsoncolor v0.3.0
 	github.com/segmentio/encoding v0.1.14
 	github.com/stretchr/testify v1.7.0
-	golang.org/x/sys v0.0.0-20210915083310-ed5796bab164 // indirect
-	golang.org/x/term v0.0.0-20210615171337-6886f2dfbf5b
+	golang.org/x/sys v0.14.0 // indirect
 	gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 // indirect
 )
diff --git a/go.sum b/go.sum
index 095613d..dfb2105 100644
--- a/go.sum
+++ b/go.sum
@@ -19,6 +19,8 @@ github.com/mattn/go-isatty v0.0.11/go.mod h1:PhnuNfih5lzO57/f3n+odYbM4JtupLOxQOA
 github.com/mattn/go-isatty v0.0.12/go.mod h1:cbi8OIDigv2wuxKPP5vlRcQ1OAZbq2CE4Kysco4FUpU=
 github.com/mattn/go-isatty v0.0.14 h1:yVuAays6BHfxijgZPzw+3Zlu5yQgKGP2/hcQbHb7S9Y=
 github.com/mattn/go-isatty v0.0.14/go.mod h1:7GGIvUiUoEMVVmxf/4nioHXj79iQHKdU27kJ6hsGG94=
+github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
+github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
 github.com/nwidger/jsoncolor v0.3.0 h1:VdTH8Dc0SJoq4pJ8pRxxFZW0/5Ng5akbN4YToCBJDSU=
 github.com/nwidger/jsoncolor v0.3.0/go.mod h1:Cs34umxLbJvgBMnVNVqhji9BhoT/N/KinHqZptQ7cf4=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
@@ -32,12 +34,12 @@ golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5h
 golang.org/x/sys v0.0.0-20191026070338-33540a1f6037/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200116001909-b77594299b42/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200223170610-d5e6a3e2c0ae/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20210915083310-ed5796bab164 h1:7ZDGnxgHAMw7thfC5bEos0RDAccZKxioiWBhfIe+tvw=
 golang.org/x/sys v0.0.0-20210915083310-ed5796bab164/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/term v0.0.0-20210615171337-6886f2dfbf5b h1:9zKuko04nR4gjZ4+DNjHqRlAJqbJETHwiNKDqTfOjfE=
-golang.org/x/term v0.0.0-20210615171337-6886f2dfbf5b/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
+golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.14.0 h1:Vz7Qs629MkJkGyHxUlRHizWJRG2j8fbQKjELVSNhy7Q=
+golang.org/x/sys v0.14.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
diff --git a/jsoncolor.go b/jsoncolor.go
index 3d2b189..2edc941 100644
--- a/jsoncolor.go
+++ b/jsoncolor.go
@@ -6,8 +6,6 @@ import (
 	"strconv"
 
 	"github.com/mattn/go-isatty"
-
-	"golang.org/x/term"
 )
 
 // Colors specifies colorization of JSON output. Each field
@@ -153,32 +151,23 @@ func IsColorTerminal(w io.Writer) bool {
 		return false
 	}
 
-	if !isTerminal(w) {
+	f, ok := w.(*os.File)
+	if !ok {
 		return false
 	}
+	fd := f.Fd()
 
-	if os.Getenv("TERM") == "dumb" {
+	if !isatty.IsTerminal(fd) {
 		return false
 	}
 
-	f, ok := w.(*os.File)
-	if !ok {
+	if os.Getenv("TERM") == "dumb" {
 		return false
 	}
 
-	if isatty.IsCygwinTerminal(f.Fd()) {
+	if isatty.IsCygwinTerminal(fd) {
 		return false
 	}
 
 	return true
 }
-
-// isTerminal returns true if w is a terminal.
-func isTerminal(w io.Writer) bool {
-	switch v := w.(type) {
-	case *os.File:
-		return term.IsTerminal(int(v.Fd()))
-	default:
-		return false
-	}
-}
diff --git a/parse.go b/parse.go
index 38102fa..0f43b4c 100644
--- a/parse.go
+++ b/parse.go
@@ -7,8 +7,6 @@ import (
 	"unicode"
 	"unicode/utf16"
 	"unicode/utf8"
-
-	"github.com/segmentio/encoding/ascii"
 )
 
 // All spaces characters defined in the json specification.
@@ -398,7 +396,7 @@ func parseStringFast(b []byte) ([]byte, []byte, bool, error) {
 	if n <= 1 {
 		return nil, b[len(b):], false, syntaxError(b, "missing '\"' at the end of a string value")
 	}
-	if bytes.IndexByte(b[1:n], '\\') < 0 && ascii.ValidPrint(b[1:n]) {
+	if bytes.IndexByte(b[1:n], '\\') < 0 && asciiValidPrint(b[1:n]) {
 		return b[:n], b[n:], false, nil
 	}
 
@@ -706,7 +704,7 @@ func hasLeadingZeroes(b []byte) bool {
 }
 
 func appendToLower(b, s []byte) []byte {
-	if ascii.Valid(s) { // fast path for ascii strings
+	if asciiValid(s) { // fast path for ascii strings
 		i := 0
 
 		for j := range s {