diff --git a/models/user/setting_keys.go b/models/user/setting_keys.go
index 458b78e357f0..109b5dd91636 100644
--- a/models/user/setting_keys.go
+++ b/models/user/setting_keys.go
@@ -5,6 +5,8 @@
 package user
 
 const (
-	// SettingsKeyHiddenCommentTypes is the settings key for hidden comment types
+	// SettingsKeyHiddenCommentTypes is the setting key for hidden comment types
 	SettingsKeyHiddenCommentTypes = "issue.hidden_comment_types"
+	// SettingsKeyDiffWhitespaceBehavior is the setting key for whitespace behavior of diff
+	SettingsKeyDiffWhitespaceBehavior = "diff.whitespace_behaviour"
 )
diff --git a/routers/web/repo/middlewares.go b/routers/web/repo/middlewares.go
index 3ee9d1a3e98f..c99f0ee8f9e5 100644
--- a/routers/web/repo/middlewares.go
+++ b/routers/web/repo/middlewares.go
@@ -63,11 +63,29 @@ func SetDiffViewStyle(ctx *context.Context) {
 
 // SetWhitespaceBehavior set whitespace behavior as render variable
 func SetWhitespaceBehavior(ctx *context.Context) {
+	const defaultWhitespaceBehavior = "show-all"
 	whitespaceBehavior := ctx.FormString("whitespace")
 	switch whitespaceBehavior {
-	case "ignore-all", "ignore-eol", "ignore-change":
-		ctx.Data["WhitespaceBehavior"] = whitespaceBehavior
+	case "", "ignore-all", "ignore-eol", "ignore-change":
+		break
 	default:
-		ctx.Data["WhitespaceBehavior"] = ""
+		whitespaceBehavior = defaultWhitespaceBehavior
+	}
+	if ctx.IsSigned {
+		userWhitespaceBehavior, err := user_model.GetUserSetting(ctx.User.ID, user_model.SettingsKeyDiffWhitespaceBehavior, defaultWhitespaceBehavior)
+		if err == nil {
+			if whitespaceBehavior == "" {
+				whitespaceBehavior = userWhitespaceBehavior
+			} else if whitespaceBehavior != userWhitespaceBehavior {
+				_ = user_model.SetUserSetting(ctx.User.ID, user_model.SettingsKeyDiffWhitespaceBehavior, whitespaceBehavior)
+			}
+		} // else: we can ignore the error safely
+	}
+
+	// these behaviors are for gitdiff.GetWhitespaceFlag
+	if whitespaceBehavior == "" {
+		ctx.Data["WhitespaceBehavior"] = defaultWhitespaceBehavior
+	} else {
+		ctx.Data["WhitespaceBehavior"] = whitespaceBehavior
 	}
 }
diff --git a/services/gitdiff/gitdiff.go b/services/gitdiff/gitdiff.go
index 0fcb36161967..017341d63f64 100644
--- a/services/gitdiff/gitdiff.go
+++ b/services/gitdiff/gitdiff.go
@@ -1532,13 +1532,17 @@ func CommentMustAsDiff(c *models.Comment) *Diff {
 }
 
 // GetWhitespaceFlag returns git diff flag for treating whitespaces
-func GetWhitespaceFlag(whiteSpaceBehavior string) string {
+func GetWhitespaceFlag(whitespaceBehavior string) string {
 	whitespaceFlags := map[string]string{
 		"ignore-all":    "-w",
 		"ignore-change": "-b",
 		"ignore-eol":    "--ignore-space-at-eol",
-		"":              "",
+		"show-all":      "",
 	}
 
-	return whitespaceFlags[whiteSpaceBehavior]
+	if flag, ok := whitespaceFlags[whitespaceBehavior]; ok {
+		return flag
+	}
+	log.Warn("unknown whitespace behavior: %q, default to 'show-all'", whitespaceBehavior)
+	return ""
 }
diff --git a/templates/repo/diff/whitespace_dropdown.tmpl b/templates/repo/diff/whitespace_dropdown.tmpl
index 1e0e046925c4..7ea4238d6d28 100644
--- a/templates/repo/diff/whitespace_dropdown.tmpl
+++ b/templates/repo/diff/whitespace_dropdown.tmpl
@@ -2,8 +2,8 @@
 	{{.i18n.Tr "repo.diff.whitespace_button"}}
 	{{svg "octicon-triangle-down" 14 "dropdown icon"}}
 	<div class="menu">
-		<a class="item" href="?style={{if .IsSplitStyle}}split{{else}}unified{{end}}&whitespace=">
-			<i class="circle {{ if eq .WhitespaceBehavior "" }}dot{{else}}outline{{end}} icon"></i>
+		<a class="item" href="?style={{if .IsSplitStyle}}split{{else}}unified{{end}}&whitespace=show-all">
+			<i class="circle {{ if eq .WhitespaceBehavior "show-all" }}dot{{else}}outline{{end}} icon"></i>
 			{{.i18n.Tr "repo.diff.whitespace_show_everything"}}
 		</a>
 		<a class="item" href="?style={{if .IsSplitStyle}}split{{else}}unified{{end}}&whitespace=ignore-all">