diff --git a/backend/yandex/yandex.go b/backend/yandex/yandex.go
index fc40aa88b..dc35be968 100644
--- a/backend/yandex/yandex.go
+++ b/backend/yandex/yandex.go
@@ -514,11 +514,12 @@ func (f *Fs) mkDirs(ctx context.Context, path string) (err error) {
 			if apiErr.ErrorName != "DiskPathPointsToExistentDirectoryError" {
 				// 2 if it fails then create all directories in the path from root.
 				dirs := strings.Split(dirString, "/") //path separator
-				var mkdirpath = "/"                   //path separator /
+				var mkdirpath strings.Builder
+				mkdirpath.WriteString("/") //path separator /
 				for _, element := range dirs {
 					if element != "" {
-						mkdirpath += element + "/"      //path separator /
-						_ = f.CreateDir(ctx, mkdirpath) // ignore errors while creating dirs
+						mkdirpath.WriteString(element + "/")     //path separator /
+						_ = f.CreateDir(ctx, mkdirpath.String()) // ignore errors while creating dirs
 					}
 				}
 			}
diff --git a/cmd/bisync/bisync_debug_test.go b/cmd/bisync/bisync_debug_test.go
index 45134730d..ecb14adf1 100644
--- a/cmd/bisync/bisync_debug_test.go
+++ b/cmd/bisync/bisync_debug_test.go
@@ -98,7 +98,7 @@ func (b *bisyncTest) generateDebuggers() {
 	}
 
 	variations := []string{"LocalRemote", "RemoteLocal", "RemoteRemote"}
-	debuggers := ""
+	var debuggers strings.Builder
 
 	for _, backend := range config.Backends {
 		if backend.Remote == "" {
@@ -113,17 +113,17 @@ func (b *bisyncTest) generateDebuggers() {
 				name := fmt.Sprintf("Test %s %s %s", backend.Remote, testcase, variation)
 				switch variation {
 				case "LocalRemote":
-					debuggers += fmt.Sprintf(debugFormat, name, "local", backend.Remote, testcase)
+					debuggers.WriteString(fmt.Sprintf(debugFormat, name, "local", backend.Remote, testcase))
 				case "RemoteLocal":
-					debuggers += fmt.Sprintf(debugFormat, name, backend.Remote, "local", testcase)
+					debuggers.WriteString(fmt.Sprintf(debugFormat, name, backend.Remote, "local", testcase))
 				case "RemoteRemote":
-					debuggers += fmt.Sprintf(debugFormat, name, backend.Remote, backend.Remote, testcase)
+					debuggers.WriteString(fmt.Sprintf(debugFormat, name, backend.Remote, backend.Remote, testcase))
 				}
 			}
 		}
 	}
 
-	out := fmt.Sprintf(docFormat, debuggers)
+	out := fmt.Sprintf(docFormat, debuggers.String())
 	outpath := "./testdata/bisync_vscode_debuggers_launch.json"
 	err = os.WriteFile(outpath, []byte(out), bilib.PermSecure)
 	assert.NoError(b.t, err, "writing golden file %s", outpath)
diff --git a/cmd/cryptdecode/cryptdecode.go b/cmd/cryptdecode/cryptdecode.go
index 0d66877ff..56acf8fe6 100644
--- a/cmd/cryptdecode/cryptdecode.go
+++ b/cmd/cryptdecode/cryptdecode.go
@@ -4,6 +4,7 @@ package cryptdecode
 import (
 	"errors"
 	"fmt"
+	"strings"
 
 	"github.com/rclone/rclone/backend/crypt"
 	"github.com/rclone/rclone/cmd"
@@ -67,32 +68,32 @@ command. See the documentation on the [crypt](/crypt/) overlay for more info.`,
 
 // cryptDecode returns the unencrypted file name
 func cryptDecode(cipher *crypt.Cipher, args []string) error {
-	output := ""
+	var output strings.Builder
 
 	for _, encryptedFileName := range args {
 		fileName, err := cipher.DecryptFileName(encryptedFileName)
 		if err != nil {
-			output += fmt.Sprintln(encryptedFileName, "\t", "Failed to decrypt")
+			output.WriteString(fmt.Sprintln(encryptedFileName, "\t", "Failed to decrypt"))
 		} else {
-			output += fmt.Sprintln(encryptedFileName, "\t", fileName)
+			output.WriteString(fmt.Sprintln(encryptedFileName, "\t", fileName))
 		}
 	}
 
-	fmt.Print(output)
+	fmt.Print(output.String())
 
 	return nil
 }
 
 // cryptEncode returns the encrypted file name
 func cryptEncode(cipher *crypt.Cipher, args []string) error {
-	output := ""
+	var output strings.Builder
 
 	for _, fileName := range args {
 		encryptedFileName := cipher.EncryptFileName(fileName)
-		output += fmt.Sprintln(fileName, "\t", encryptedFileName)
+		output.WriteString(fmt.Sprintln(fileName, "\t", encryptedFileName))
 	}
 
-	fmt.Print(output)
+	fmt.Print(output.String())
 
 	return nil
 }
diff --git a/cmd/lsf/lsf_test.go b/cmd/lsf/lsf_test.go
index 886acbcf0..45cc76085 100644
--- a/cmd/lsf/lsf_test.go
+++ b/cmd/lsf/lsf_test.go
@@ -3,6 +3,7 @@ package lsf
 import (
 	"bytes"
 	"context"
+	"strings"
 	"testing"
 
 	_ "github.com/rclone/rclone/backend/local"
@@ -140,12 +141,12 @@ file3
 	require.NoError(t, err)
 
 	items, _ := list.DirSorted(context.Background(), f, true, "")
-	var expectedOutput string
+	var expectedOutput strings.Builder
 	for _, item := range items {
-		expectedOutput += item.ModTime(context.Background()).Format("2006-01-02 15:04:05") + "\n"
+		expectedOutput.WriteString(item.ModTime(context.Background()).Format("2006-01-02 15:04:05") + "\n")
 	}
 
-	assert.Equal(t, expectedOutput, buf.String())
+	assert.Equal(t, expectedOutput.String(), buf.String())
 
 	buf = new(bytes.Buffer)
 	format = "sp"