diff --git a/src/html/template/css.go b/src/html/template/css.go
index 1587af8385..eb92fc92b5 100644
--- a/src/html/template/css.go
+++ b/src/html/template/css.go
@@ -7,6 +7,7 @@ package template
 import (
 	"bytes"
 	"fmt"
+	"strings"
 	"unicode"
 	"unicode/utf8"
 )
@@ -156,7 +157,7 @@ func isCSSSpace(b byte) bool {
 // cssEscaper escapes HTML and CSS special characters using \<hex>+ escapes.
 func cssEscaper(args ...interface{}) string {
 	s, _ := stringify(args...)
-	var b bytes.Buffer
+	var b strings.Builder
 	r, w, written := rune(0), 0, 0
 	for i := 0; i < len(s); i += w {
 		// See comment in htmlEscaper.
@@ -168,6 +169,9 @@ func cssEscaper(args ...interface{}) string {
 		default:
 			continue
 		}
+		if written == 0 {
+			b.Grow(len(s))
+		}
 		b.WriteString(s[written:i])
 		b.WriteString(repl)
 		written = i + w
diff --git a/src/html/template/html.go b/src/html/template/html.go
index 2ea5a7d4bc..13a0cd0436 100644
--- a/src/html/template/html.go
+++ b/src/html/template/html.go
@@ -137,7 +137,7 @@ var htmlNospaceNormReplacementTable = []string{
 // htmlReplacer returns s with runes replaced according to replacementTable
 // and when badRunes is true, certain bad runes are allowed through unescaped.
 func htmlReplacer(s string, replacementTable []string, badRunes bool) string {
-	written, b := 0, new(bytes.Buffer)
+	written, b := 0, new(strings.Builder)
 	r, w := rune(0), 0
 	for i := 0; i < len(s); i += w {
 		// Cannot use 'for range s' because we need to preserve the width
@@ -146,6 +146,9 @@ func htmlReplacer(s string, replacementTable []string, badRunes bool) string {
 		r, w = utf8.DecodeRuneInString(s[i:])
 		if int(r) < len(replacementTable) {
 			if repl := replacementTable[r]; len(repl) != 0 {
+				if written == 0 {
+					b.Grow(len(s))
+				}
 				b.WriteString(s[written:i])
 				b.WriteString(repl)
 				written = i + w
@@ -154,6 +157,9 @@ func htmlReplacer(s string, replacementTable []string, badRunes bool) string {
 			// No-op.
 			// IE does not allow these ranges in unquoted attrs.
 		} else if 0xfdd0 <= r && r <= 0xfdef || 0xfff0 <= r && r <= 0xffff {
+			if written == 0 {
+				b.Grow(len(s))
+			}
 			fmt.Fprintf(b, "%s&#x%x;", s[written:i], r)
 			written = i + w
 		}
diff --git a/src/html/template/js.go b/src/html/template/js.go
index 872f6786b3..04c7c325db 100644
--- a/src/html/template/js.go
+++ b/src/html/template/js.go
@@ -187,7 +187,7 @@ func jsValEscaper(args ...interface{}) string {
 	}
 	first, _ := utf8.DecodeRune(b)
 	last, _ := utf8.DecodeLastRune(b)
-	var buf bytes.Buffer
+	var buf strings.Builder
 	// Prevent IdentifierNames and NumericLiterals from running into
 	// keywords: in, instanceof, typeof, void
 	pad := isJSIdentPart(first) || isJSIdentPart(last)
@@ -217,7 +217,7 @@ func jsValEscaper(args ...interface{}) string {
 		if pad {
 			buf.WriteByte(' ')
 		}
-		b = buf.Bytes()
+		return buf.String()
 	}
 	return string(b)
 }
@@ -253,7 +253,7 @@ func jsRegexpEscaper(args ...interface{}) string {
 // It also replaces runes U+2028 and U+2029 with the raw strings `\u2028` and
 // `\u2029`.
 func replace(s string, replacementTable []string) string {
-	var b bytes.Buffer
+	var b strings.Builder
 	r, w, written := rune(0), 0, 0
 	for i := 0; i < len(s); i += w {
 		// See comment in htmlEscaper.
@@ -269,6 +269,9 @@ func replace(s string, replacementTable []string) string {
 		default:
 			continue
 		}
+		if written == 0 {
+			b.Grow(len(s))
+		}
 		b.WriteString(s[written:i])
 		b.WriteString(repl)
 		written = i + w