diff --git a/src/family.rs b/src/family.rs
index 90c6eae..28c93b3 100644
--- a/src/family.rs
+++ b/src/family.rs
@@ -40,7 +40,7 @@ impl<'a> Family<'a> {
     }
 }
 
-pub fn group_by_family_sort_by_name(faces: &Vec<FaceInfo>) -> Vec<Family<'_>> {
+pub fn group_by_family_sort_by_name(faces: &[FaceInfo]) -> Vec<Family<'_>> {
     let mut families = HashMap::new();
 
     faces.iter().for_each(|face| {
@@ -56,5 +56,5 @@ pub fn group_by_family_sort_by_name(faces: &Vec<FaceInfo>) -> Vec<Family<'_>> {
         family.faces.sort_unstable_by(|a, b| a.name.cmp(&b.name))
     }
 
-    return families;
+    families
 }
diff --git a/src/loader/mod.rs b/src/loader/mod.rs
index 2b76f12..0ae2793 100644
--- a/src/loader/mod.rs
+++ b/src/loader/mod.rs
@@ -43,7 +43,7 @@ pub fn faces_contains(c: char) -> Vec<FaceInfo> {
                 }
             }
 
-            return face.transpose();
+            face.transpose()
         })
         .filter_map(|f| f.ok())
         .collect()
diff --git a/src/preview/browser/builder.rs b/src/preview/browser/builder.rs
index 0c3c755..380c192 100644
--- a/src/preview/browser/builder.rs
+++ b/src/preview/browser/builder.rs
@@ -16,7 +16,7 @@
 // You should have received a copy of the GNU General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
-use std::iter::FromIterator;
+use std::{fmt::Write, iter::FromIterator};
 
 use super::SingleThreadServer;
 use crate::family::Family;
@@ -43,21 +43,23 @@ impl<'a> Builder<'a> {
     }
 
     fn build_html(self, c: char) -> String {
+        let font_previews =
+            self.families.into_iter().fold(String::new(), |mut acc: String, family| {
+                write!(
+                    &mut acc,
+                    include_str!("statics/preview_block_template.html"),
+                    char = c,
+                    family = family,
+                )
+                .expect("write to string should always success");
+                acc
+            });
+
         format!(
             include_str!("statics/template.html"),
             style = include_str!("statics/style.css"),
             script = include_str!("statics/script.js"),
-            font_previews = self
-                .families
-                .into_iter()
-                .map(|family| {
-                    format!(
-                        include_str!("statics/preview_block_template.html"),
-                        char = c,
-                        family = family
-                    )
-                })
-                .collect::<String>()
+            font_previews = font_previews,
         )
     }
 
diff --git a/src/preview/terminal/ui/mod.rs b/src/preview/terminal/ui/mod.rs
index 41b2d9d..dcd5112 100644
--- a/src/preview/terminal/ui/mod.rs
+++ b/src/preview/terminal/ui/mod.rs
@@ -59,7 +59,7 @@ pub struct UI<'a> {
 
 impl<'a: 'a> UI<'a> {
     pub fn new(c: char, families: Vec<Family<'a>>) -> Option<Self> {
-        if families.len() > 0 {
+        if !families.is_empty() {
             Some(Self { state: State::new(c, families), idle_redraw: 0 })
         } else {
             None
diff --git a/src/rasterizer/bitmap.rs b/src/rasterizer/bitmap.rs
index 44d35ec..58ceca9 100644
--- a/src/rasterizer/bitmap.rs
+++ b/src/rasterizer/bitmap.rs
@@ -25,6 +25,7 @@ pub struct Metrics {
     pub width: usize,
 }
 
+#[allow(dead_code)] // TODO: remove this
 pub struct Bitmap {
     pixel_mode: u8,
     pitch: u32,
@@ -33,7 +34,8 @@ pub struct Bitmap {
 }
 
 impl Bitmap {
-    pub(super) fn new(_font_face: FontFace) -> Self {
+    #[allow(dead_code)] // remove this
+    pub fn new(_font_face: FontFace) -> Self {
         // let face_rec = unsafe { &*font_face.face };
         // let glyph = unsafe { &*face_rec.glyph };
         // let left = glyph.bitmap_left;
diff --git a/src/rasterizer/font_face.rs b/src/rasterizer/font_face.rs
index 0d898ac..1db36bf 100644
--- a/src/rasterizer/font_face.rs
+++ b/src/rasterizer/font_face.rs
@@ -19,6 +19,7 @@
 use crate::rasterizer::bitmap::Bitmap;
 
 pub struct FontFace {
+    #[allow(dead_code)] // TODO: remove this
     face: owned_ttf_parser::OwnedFace,
     height: u32,
     width: u32,