diff --git a/proc_macros/proc_macros.rs b/proc_macros/proc_macros.rs
index d2e6ca6..225d675 100644
--- a/proc_macros/proc_macros.rs
+++ b/proc_macros/proc_macros.rs
@@ -978,7 +978,7 @@ pub fn print_error(item: TokenStream) -> TokenStream {
         match (#expr) {
             Ok(re) => re,
             Err(e) => {
-                println!("{}{}", #msg, e);
+                log::error!("{}{}", #msg, e);
                 return #re;
             }
         }
diff --git a/src/cookies.rs b/src/cookies.rs
index 84d492e..a3edbe0 100644
--- a/src/cookies.rs
+++ b/src/cookies.rs
@@ -76,7 +76,7 @@ impl Cookie {
         let mut expired: i64 = 0;
         let u = url.into_url();
         if u.is_err() {
-            println!(
+            log::warn!(
                 "{} {}",
                 gettext("Warning: Failed to parse URL:"),
                 u.unwrap_err()
@@ -91,7 +91,7 @@ impl Cookie {
         let t = String::from(m);
         let l2: Vec<&str> = t.split("=").collect();
         if l2.len() < 2 {
-            println!(
+            log::warn!(
                 "{} {}",
                 gettext("Warning: Failed to parse cookie's key and value:"),
                 m
@@ -110,7 +110,7 @@ impl Cookie {
             let k = ll[0].to_lowercase();
             if k == "expires" {
                 if ll.len() < 2 {
-                    println!("{}", gettext("Warning: Expires need a date."));
+                    log::warn!("{}", gettext("Warning: Expires need a date."));
                     return None;
                 }
                 let mut re = dateparser::parse(ll[1]);
@@ -118,7 +118,7 @@ impl Cookie {
                     let s = ll[1].replace("-", " ");
                     re = dateparser::parse(s.as_str());
                     if re.is_err() {
-                        println!(
+                        log::warn!(
                             "{} {}",
                             gettext("Failed to parse UTC string:"),
                             re.unwrap_err()
@@ -130,12 +130,12 @@ impl Cookie {
                 expired = r.timestamp();
             } else if k == "max-age" {
                 if ll.len() < 2 {
-                    println!("{}", gettext("Warning: Max-Age need a duration."));
+                    log::warn!("{}", gettext("Warning: Max-Age need a duration."));
                     return None;
                 }
                 let re = ll[1].parse::<i64>();
                 if re.is_err() {
-                    println!(
+                    log::warn!(
                         "{} {}",
                         gettext("Failed to parse Max-Age:"),
                         re.unwrap_err()
@@ -145,18 +145,18 @@ impl Cookie {
                 expired = re.unwrap() + Utc::now().timestamp();
             } else if k == "domain" {
                 if ll.len() < 2 {
-                    println!("{}", gettext("Warning: Domain need a domain."));
+                    log::warn!("{}", gettext("Warning: Domain need a domain."));
                     return None;
                 }
                 domain = Some(String::from(ll[1]));
             } else if k == "path" {
                 if ll.len() < 2 {
-                    println!("{}", gettext("Warning: Path need a path."));
+                    log::warn!("{}", gettext("Warning: Path need a path."));
                     return None;
                 }
                 let p = ll[1].to_string();
                 if !p.starts_with("/") {
-                    println!(
+                    log::warn!(
                         "{} {}",
                         gettext("Warning: path is not starts with \"/\":"),
                         p.as_str()
@@ -171,7 +171,7 @@ impl Cookie {
             }
         }
         if domain.is_none() {
-            println!("{}", gettext("Warning: Failed to get domain."));
+            log::warn!("{}", gettext("Warning: Failed to get domain."));
             return None;
         }
         let domain = domain.unwrap();
@@ -221,7 +221,7 @@ impl Cookie {
     pub fn matched<U: IntoUrl>(&self, url: U) -> bool {
         let u = url.into_url();
         if u.is_err() {
-            println!(
+            log::warn!(
                 "{} {}",
                 gettext("Warning: Failed to parse URL:"),
                 u.unwrap_err()
@@ -367,12 +367,12 @@ impl CookieJar {
         self.cookies.clear();
         let p = file_name.as_ref();
         if !p.exists() {
-            println!("{} {}", gettext("Can not find file:"), p.display());
+            log::error!("{} {}", gettext("Can not find file:"), p.display());
             return false;
         }
         let re = File::open(p);
         if re.is_err() {
-            println!("{} {}", gettext("Can not open file:"), p.display());
+            log::error!("{} {}", gettext("Can not open file:"), p.display());
             return false;
         }
         let f = re.unwrap();
@@ -386,7 +386,7 @@ impl CookieJar {
             }
             let mut s = l.split('\t');
             if s.clone().count() < 7 {
-                println!("{} {}", gettext("Invalid cookie:"), l);
+                log::error!("{} {}", gettext("Invalid cookie:"), l);
                 return false;
             }
             let domain = s.next().unwrap();
@@ -398,7 +398,7 @@ impl CookieJar {
             let value = s.next().unwrap();
             let tmp = expired.trim().parse::<i64>();
             if tmp.is_err() {
-                println!("{} {}", gettext("Can not parse expired time:"), expired);
+                log::error!("{} {}", gettext("Can not parse expired time:"), expired);
                 return false;
             }
             let tmp = tmp.unwrap();
@@ -423,20 +423,20 @@ impl CookieJar {
         if p.exists() {
             let re = remove_file(p);
             if re.is_err() {
-                println!("{} {}", gettext("Failed to remove file:"), re.unwrap_err());
+                log::error!("{} {}", gettext("Failed to remove file:"), re.unwrap_err());
                 return false;
             }
         }
         let re = File::create(p);
         if re.is_err() {
-            println!("{} {}", gettext("Failed to create file:"), re.unwrap_err());
+            log::error!("{} {}", gettext("Failed to create file:"), re.unwrap_err());
             return false;
         }
         let mut f = re.unwrap();
         for c in self.cookies.iter() {
             let r = write!(f, "{}", c.to_netscape_str().as_str());
             if r.is_err() {
-                println!("{} {}", gettext("Failed to write file:"), r.unwrap_err());
+                log::error!("{} {}", gettext("Failed to write file:"), r.unwrap_err());
                 return false;
             }
         }
@@ -517,7 +517,7 @@ impl CookieJarManager {
                 *count -= 1;
                 if *count == 0 {
                     if !jar.get_mut().save(&path) {
-                        println!(
+                        log::warn!(
                             "{} {}",
                             gettext("Warning: Failed to save cookies file:"),
                             path.display()
diff --git a/src/data/data.rs b/src/data/data.rs
index b8845b5..5d047de 100644
--- a/src/data/data.rs
+++ b/src/data/data.rs
@@ -128,7 +128,7 @@ impl PixivData {
                         self.description = Some(s);
                     }
                     Err(s) => {
-                        println!("{} {}", gettext("Failed to unescape string:"), s.as_str());
+                        log::warn!("{} {}", gettext("Failed to unescape string:"), s.as_str());
                     }
                 }
             }
diff --git a/src/data/json.rs b/src/data/json.rs
index 93e2899..f084164 100644
--- a/src/data/json.rs
+++ b/src/data/json.rs
@@ -45,7 +45,7 @@ impl JSONDataFile {
         if p.exists() {
             let r = remove_file(p);
             if r.is_err() {
-                println!("{} {}", gettext("Failed to remove file:"), r.unwrap_err());
+                log::error!("{} {}", gettext("Failed to remove file:"), r.unwrap_err());
                 return false;
             }
         }
@@ -56,13 +56,13 @@ impl JSONDataFile {
         let value = value.unwrap();
         let f = File::create(p);
         if f.is_err() {
-            println!("{} {}", gettext("Failed to create file:"), f.unwrap_err());
+            log::error!("{} {}", gettext("Failed to create file:"), f.unwrap_err());
             return false;
         }
         let mut f = f.unwrap();
         let r = f.write(value.pretty(2).as_bytes());
         if r.is_err() {
-            println!("{} {}", gettext("Failed to write file:"), r.unwrap_err());
+            log::error!("{} {}", gettext("Failed to write file:"), r.unwrap_err());
             return false;
         }
         true
diff --git a/src/download.rs b/src/download.rs
index 50572c9..8279686 100644
--- a/src/download.rs
+++ b/src/download.rs
@@ -75,14 +75,14 @@ impl Main {
                     if !fc.is_inited() {
                         let helper = get_helper();
                         if !fc.init(helper.cookies()) {
-                            println!("{}", gettext("Failed to initialize fanbox api client."));
+                            log::error!("{}", gettext("Failed to initialize fanbox api client."));
                             return 1;
                         }
                         if !fc.check_login().await {
                             return 1;
                         }
                         if !fc.logined() {
-                            println!("{}", gettext("Warning: Fanbox client is not logged in."));
+                            log::warn!("{}", gettext("Warning: Fanbox client is not logged in."));
                         }
                     }
                     tasks
@@ -96,14 +96,14 @@ impl Main {
                     if !fc.is_inited() {
                         let helper = get_helper();
                         if !fc.init(helper.cookies()) {
-                            println!("{}", gettext("Failed to initialize fanbox api client."));
+                            log::error!("{}", gettext("Failed to initialize fanbox api client."));
                             return 1;
                         }
                         if !fc.check_login().await {
                             return 1;
                         }
                         if !fc.logined() {
-                            println!("{}", gettext("Warning: Fanbox client is not logged in."));
+                            log::warn!("{}", gettext("Warning: Fanbox client is not logged in."));
                         }
                     }
                     tasks
@@ -131,7 +131,7 @@ impl Main {
             match result {
                 Ok(_) => {}
                 Err(e) => {
-                    println!("{} {}", gettext("Failed to download post:"), e);
+                    log::error!("{} {}", gettext("Failed to download post:"), e);
                     re = 1;
                 }
             }
@@ -174,7 +174,7 @@ impl Main {
             match result {
                 Ok(_) => {}
                 Err(e) => {
-                    println!("{} {}", gettext("Failed to download url:"), e);
+                    log::error!("{} {}", gettext("Failed to download url:"), e);
                     re = 1;
                 }
             }
@@ -218,7 +218,7 @@ pub async fn download_artwork_link<L: IntoUrl + Clone>(
                 #[cfg(feature = "exif")]
                 {
                     if add_exifdata_to_image(&file_name, &datas, np).is_err() {
-                        println!(
+                        log::warn!(
                             "{} {}",
                             gettext("Failed to add exif data to image:"),
                             file_name.to_str().unwrap_or("(null)")
@@ -237,7 +237,7 @@ pub async fn download_artwork_link<L: IntoUrl + Clone>(
             {
                 if helper.update_exif() && file_name.exists() {
                     if add_exifdata_to_image(&file_name, &datas, np).is_err() {
-                        println!(
+                        log::warn!(
                             "{} {}",
                             gettext("Failed to add exif data to image:"),
                             file_name.to_str().unwrap_or("(null)")
@@ -262,7 +262,7 @@ pub async fn download_artwork(
             if e.is_not_found() {
                 return Err(e);
             }
-            println!("{}{}", gettext("Warning: Failed to download artwork with app api, trying to download with web api: "), e);
+            log::warn!("{}{}", gettext("Warning: Failed to download artwork with app api, trying to download with web api: "), e);
             download_artwork_web(pw.clone(), id).await?;
         }
     } else if app_ok {
@@ -319,7 +319,7 @@ pub async fn download_artwork_ugoira(
         let metadata = match get_video_metadata(Arc::clone(&datas).as_ref()) {
             Ok(m) => m,
             Err(e) => {
-                println!(
+                log::warn!(
                     "{} {}",
                     gettext("Warning: Failed to generate video's metadata:"),
                     e
@@ -351,7 +351,7 @@ pub async fn download_artwork_ugoira(
             &options,
             &metadata,
         )?;
-        println!(
+        log::info!(
             "{}",
             gettext("Converted <src> -> <dest>")
                 .replace("<src>", file_name.to_str().unwrap_or("(null)"))
@@ -398,7 +398,7 @@ pub async fn download_artwork_app(
     }
     if helper.add_history() && !web_used {
         if let Err(e) = ac.add_illust_to_browsing_history(vec![id]).await {
-            println!(
+            log::warn!(
                 "{} {}",
                 gettext("Warning: Failed to add artwork to history:"),
                 e
@@ -421,7 +421,7 @@ pub async fn download_artwork_app(
             _ => {}
         },
         None => {
-            println!("{}", gettext("Warning: Failed to get illust's type."));
+            log::warn!("{}", gettext("Warning: Failed to get illust's type."));
         }
     }
     let page_count = data
@@ -534,10 +534,10 @@ pub async fn download_artwork_web(
 ) -> Result<(), PixivDownloaderError> {
     if !pw.is_login_checked() {
         if !pw.check_login().await {
-            println!("{}", gettext("Failed to check login status."));
+            log::error!("{}", gettext("Failed to check login status."));
         } else {
             if !pw.logined() {
-                println!(
+                log::warn!(
                     "{}",
                     gettext("Warning: Web api client not logged in, some future may not work.")
                 );
@@ -602,7 +602,7 @@ pub async fn download_artwork_web(
                 return download_artwork_ugoira(pw, id, base, datas).await;
             }
             _ => {
-                println!(
+                log::warn!(
                     "{} {}",
                     gettext("Warning: Unknown illust type:"),
                     illust_type
@@ -610,7 +610,7 @@ pub async fn download_artwork_web(
             }
         }
     } else {
-        println!("{}", gettext("Warning: Failed to get illust's type."));
+        log::warn!("{}", gettext("Warning: Failed to get illust's type."));
     }
     if pages_data.is_some() && helper.download_multiple_files() {
         let mut np = 0u16;
@@ -791,7 +791,7 @@ pub async fn download_fanbox_image(
                 #[cfg(feature = "exif")]
                 {
                     if add_exifdata_to_image(&file_name, &datas, np).is_err() {
-                        println!(
+                        log::warn!(
                             "{} {}",
                             gettext("Failed to add exif data to image:"),
                             file_name.to_str().unwrap_or("(null)")
@@ -810,7 +810,7 @@ pub async fn download_fanbox_image(
             {
                 if helper.update_exif() && file_name.exists() {
                     if add_exifdata_to_image(&file_name, &datas, np).is_err() {
-                        println!(
+                        log::warn!(
                             "{} {}",
                             gettext("Failed to add exif data to image:"),
                             file_name.to_str().unwrap_or("(null)")
@@ -1129,7 +1129,7 @@ pub async fn download_fanbox_creator_info(
     match data.check_unknown() {
         Ok(_) => {}
         Err(e) => {
-            println!(
+            log::warn!(
                 "{} {}",
                 gettext("Warning: Creator's info contains unknown data:"),
                 e
diff --git a/src/downloader/downloader.rs b/src/downloader/downloader.rs
index 760a119..044ee8c 100644
--- a/src/downloader/downloader.rs
+++ b/src/downloader/downloader.rs
@@ -224,7 +224,7 @@ impl<T: Write + Seek + Send + Sync + ClearFile + GetTargetFileName + SetLen> Dow
     pub fn enable_multiple_download(&self) {
         self.multi.qstore(true);
         if !self.is_multi_threads() {
-            println!(
+            log::warn!(
                 "{}",
                 gettext("Warning: This file will still use single thread mode to download.")
             );
@@ -232,7 +232,7 @@ impl<T: Write + Seek + Send + Sync + ClearFile + GetTargetFileName + SetLen> Dow
             match self.pd.enable_multi() {
                 Ok(_) => {}
                 Err(e) => {
-                    println!("{}", e);
+                    log::error!("{}", e);
                 }
             }
         }
@@ -265,7 +265,7 @@ impl<T: Write + Seek + Send + Sync + ClearFile + GetTargetFileName + SetLen> Dow
         match self.pd.disable_multi() {
             Ok(_) => {}
             Err(e) => {
-                println!("{}", e);
+                log::error!("{}", e);
             }
         };
     }
@@ -608,7 +608,7 @@ impl<T: Write + Seek + Send + Sync + ClearFile + GetTargetFileName + SetLen + 's
             {
                 Ok(_) => {}
                 Err(e) => {
-                    println!("{}", e);
+                    log::error!("{}", e);
                 }
             }
         }
diff --git a/src/downloader/pd_file/file.rs b/src/downloader/pd_file/file.rs
index 11ea188..6ff07a8 100644
--- a/src/downloader/pd_file/file.rs
+++ b/src/downloader/pd_file/file.rs
@@ -494,7 +494,7 @@ impl PdFile {
         match self.remove_pd_file() {
             Ok(_) => {}
             Err(e) => {
-                println!("{} {}", gettext("Failed to remove file: "), e);
+                log::error!("{} {}", gettext("Failed to remove file: "), e);
             }
         }
     }
@@ -692,7 +692,7 @@ impl Drop for PdFile {
             match self.write() {
                 Ok(_) => {}
                 Err(e) => {
-                    println!("{}", e);
+                    log::error!("{}", e);
                     self.force_close();
                     self.remove_pd_file_with_err_msg();
                 }
diff --git a/src/downloader/tasks.rs b/src/downloader/tasks.rs
index 5ee7792..fb54ae1 100644
--- a/src/downloader/tasks.rs
+++ b/src/downloader/tasks.rs
@@ -181,7 +181,7 @@ pub async fn create_download_tasks_multi_first<
                     }
                 }
                 Err(e) => {
-                    println!("{}", e)
+                    log::error!("{}", e)
                 }
             }
             if d.enabled_progress_bar() {
@@ -199,7 +199,7 @@ pub async fn create_download_tasks_multi_first<
     match d.pd.initialize_part_datas() {
         Ok(_) => {}
         Err(e) => {
-            println!("{}", e);
+            log::error!("{}", e);
         }
     }
     if d.enabled_progress_bar() {
@@ -436,7 +436,7 @@ pub async fn check_tasks<
                         }
                     }
                     Err(e) => {
-                        println!("{}", e);
+                        log::error!("{}", e);
                         if !d.is_multi_threads() {
                             match d.get_retry_duration() {
                                 Some(d) => dur = Some(d),
@@ -506,7 +506,7 @@ pub async fn check_tasks<
                             }
                         }
                         Err(e) => {
-                            println!("{}", e);
+                            log::error!("{}", e);
                         }
                     }
                 }
diff --git a/src/error.rs b/src/error.rs
index 8f854ca..97b134c 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -69,7 +69,7 @@ macro_rules! concat_pixiv_downloader_error {
             Err(e) => match $exp2 {
                 Ok(_) => Err(e),
                 Err(e2) => {
-                    println!("{}", e);
+                    log::error!("{}", e);
                     Err(PixivDownloaderError::from(e2))
                 }
             },
@@ -88,7 +88,7 @@ macro_rules! concat_error {
             Err(e) => match $exp2 {
                 Ok(_) => Err(e),
                 Err(e2) => {
-                    println!("{}", e);
+                    log::error!("{}", e);
                     Err(<$typ>::from(e2))
                 }
             },
diff --git a/src/fanbox/paginated_creator_posts.rs b/src/fanbox/paginated_creator_posts.rs
index 70a7fb8..4ed8c21 100644
--- a/src/fanbox/paginated_creator_posts.rs
+++ b/src/fanbox/paginated_creator_posts.rs
@@ -64,7 +64,7 @@ impl PaginatedCreatorPosts {
                 Some(d) => match FanboxItemList::new(&d["body"], Arc::clone(&self.client)) {
                     Ok(d) => Some(d),
                     Err(e) => {
-                        println!("{} {}", gettext("Failed to parse posts's data:"), e);
+                        log::error!("{} {}", gettext("Failed to parse posts's data:"), e);
                         None
                     }
                 },
diff --git a/src/log_cfg.rs b/src/log_cfg.rs
index 0028e65..a9bca3b 100644
--- a/src/log_cfg.rs
+++ b/src/log_cfg.rs
@@ -29,5 +29,5 @@ pub fn init_with_level(level: LevelFilter) {
 }
 
 pub fn init_default() {
-    init_with_level(LevelFilter::Warn);
+    init_with_level(LevelFilter::Info);
 }
diff --git a/src/main.rs b/src/main.rs
index 745b8b2..ff22979 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -92,7 +92,7 @@ impl Main {
             }
             ConfigCommand::Help => {
                 let s = self.settings.as_ref().unwrap();
-                println!("{}", gettext("All available settings:"));
+                log::error!("{}", gettext("All available settings:"));
                 s.basic.print_help();
                 0
             }
@@ -145,7 +145,7 @@ impl Main {
                 let addr = get_helper().server();
                 match server::service::start_server(&addr).await {
                     Ok(server) => {
-                        println!("Listening on http://{}", addr);
+                        log::info!("Listening on http://{}", addr);
                         match server.await {
                             Ok(_) => {}
                             Err(e) => {
diff --git a/src/opt/author_name_filter.rs b/src/opt/author_name_filter.rs
index 5498e32..891f843 100644
--- a/src/opt/author_name_filter.rs
+++ b/src/opt/author_name_filter.rs
@@ -136,7 +136,7 @@ impl TryFrom<&JsonValue> for AuthorNameFilter {
 pub fn check_author_name_filters(v: &JsonValue) -> bool {
     let r = AuthorNameFilter::from_json(v);
     if r.is_err() {
-        println!(
+        log::error!(
             "{} {}",
             gettext("Failed parse author name filters:"),
             r.as_ref().unwrap_err()
diff --git a/src/opt/proxy.rs b/src/opt/proxy.rs
index e8a9420..0f3abf3 100644
--- a/src/opt/proxy.rs
+++ b/src/opt/proxy.rs
@@ -201,7 +201,7 @@ pub fn check_proxy(v: &JsonValue) -> bool {
     match ProxyChain::try_from(v) {
         Ok(_) => true,
         Err(e) => {
-            println!("{}", e);
+            log::error!("{}", e);
             false
         }
     }
diff --git a/src/parser/description.rs b/src/parser/description.rs
index 00d9f90..c74eb86 100644
--- a/src/parser/description.rs
+++ b/src/parser/description.rs
@@ -213,7 +213,6 @@ impl DescriptionParser {
             self.iter(node)
         }
         if self.nodes.len() != 0 {
-            println!();
             return Err(format!(
                 "{} {:?}",
                 gettext("There are some nodes still in stack:"),
@@ -230,7 +229,7 @@ pub fn parse_description<S: AsRef<str> + ?Sized>(desc: &S) -> Option<String> {
     match p.parse(desc) {
         Ok(_) => Some(p.data),
         Err(e) => {
-            println!("{}", e);
+            log::error!("{}", e);
             None
         }
     }
diff --git a/src/parser/metadata.rs b/src/parser/metadata.rs
index 4e87bcb..4e8464e 100644
--- a/src/parser/metadata.rs
+++ b/src/parser/metadata.rs
@@ -53,7 +53,7 @@ impl MetaDataParser {
                     }
                     let r = json::parse(c.as_ref().unwrap());
                     if r.is_err() {
-                        println!("{} {}", gettext("Failed to parse JSON:"), r.unwrap_err());
+                        log::error!("{} {}", gettext("Failed to parse JSON:"), r.unwrap_err());
                         return false;
                     }
                     self.value = Some(r.unwrap());
@@ -75,14 +75,14 @@ impl MetaDataParser {
     pub fn parse(&mut self, context: &str) -> bool {
         let r = Dom::parse(context);
         if r.is_err() {
-            println!("{} {}", gettext("Failed to parse HTML:"), r.unwrap_err());
+            log::error!("{} {}", gettext("Failed to parse HTML:"), r.unwrap_err());
             return false;
         }
         let dom = r.unwrap();
         if dom.errors.len() > 0 {
-            println!("{}", gettext("Some errors occured during parsing:"));
+            log::error!("{}", gettext("Some errors occured during parsing:"));
             for i in dom.errors.iter() {
-                println!("{}", i);
+                log::error!("{}", i);
             }
         }
         for n in dom.children.iter() {
diff --git a/src/server/service.rs b/src/server/service.rs
index 8aa5fb6..ab303d6 100644
--- a/src/server/service.rs
+++ b/src/server/service.rs
@@ -34,13 +34,13 @@ impl Service<Request<Body>> for PixivDownloaderSvc {
     }
 
     fn call(&mut self, req: Request<Body>) -> Self::Future {
-        println!("{} {}", req.method(), req.uri());
+        log::info!(target: "server", "{} {}", req.method(), req.uri());
         match self.routes.match_route(&req, &self.context) {
             Some(route) => Box::pin(async move {
                 match route.response(req).await {
                     Ok(data) => Ok(data),
                     Err(e) => {
-                        println!("{}", e);
+                        log::error!(target: "server", "{}", e);
                         Ok(Response::builder()
                             .status(500)
                             .body::<Pin<Box<HttpBodyType>>>(Box::pin(HyperBody::from(
diff --git a/src/server/timer.rs b/src/server/timer.rs
index 70a7c8a..fafc3d4 100644
--- a/src/server/timer.rs
+++ b/src/server/timer.rs
@@ -16,7 +16,7 @@ pub async fn start_timer(ctx: Arc<ServerContext>) {
         for task in tasks.take_finished_tasks() {
             let re = task.await;
             if let Ok(Err(e)) = re {
-                println!("Timer task error: {}", e);
+                log::error!("Timer task error: {}", e);
             }
         }
     }
diff --git a/src/settings.rs b/src/settings.rs
index c89c504..cf9cc80 100644
--- a/src/settings.rs
+++ b/src/settings.rs
@@ -185,7 +185,7 @@ impl SettingDesStore {
             }
             s += t.as_str();
         }
-        println!("{}", s);
+        log::error!("{}", s);
     }
 }
 
@@ -265,7 +265,7 @@ impl SettingJar {
             match v.insert(val.name().as_str(), val.value()) {
                 Ok(_) => {}
                 Err(_) => {
-                    println!("{}", gettext("Can not insert setting to JSON object."));
+                    log::error!("{}", gettext("Can not insert setting to JSON object."));
                     return None;
                 }
             }
@@ -340,7 +340,7 @@ impl SettingStore {
         }
         let re = File::open(path);
         if re.is_err() {
-            println!("{}", re.unwrap_err());
+            log::error!("{}", re.unwrap_err());
             return false;
         }
         let mut f = re.unwrap();
@@ -350,14 +350,14 @@ impl SettingStore {
             Ok(le) => {
                 if le == 0 {
                     if !fix_invalid {
-                        println!("{}", gettext("Settings file is empty."));
+                        log::error!("{}", gettext("Settings file is empty."));
                         return false;
                     }
                     return true;
                 }
             }
             Err(_) => {
-                println!("{}", gettext("Can not read from settings file."));
+                log::error!("{}", gettext("Can not read from settings file."));
                 return false;
             }
         }
@@ -366,7 +366,7 @@ impl SettingStore {
             Ok(_) => {}
             Err(_) => {
                 if !fix_invalid {
-                    println!("{}", gettext("Can not parse settings file."));
+                    log::error!("{}", gettext("Can not parse settings file."));
                     return false;
                 }
                 return true;
@@ -375,7 +375,7 @@ impl SettingStore {
         let obj = re.unwrap();
         if !obj.is_object() {
             if !fix_invalid {
-                println!("{}", gettext("Unknown settings file."));
+                log::error!("{}", gettext("Unknown settings file."));
                 return false;
             }
             return true;
@@ -387,7 +387,7 @@ impl SettingStore {
                     if !re {
                         if !fix_invalid {
                             let s = gettext("\"<key>\" is invalid, you can use \"pixiv_downloader config fix\" to remove all invalid value.").replace("<key>", key);
-                            println!("{}", s.as_str());
+                            log::error!("{}", s.as_str());
                             return false;
                         }
                     } else {
@@ -405,7 +405,7 @@ impl SettingStore {
     pub fn save(&self, file_name: &str) -> bool {
         let obj = self.data.to_json();
         if obj.is_none() {
-            println!("{}", gettext("Can not convert settings to JSON object."));
+            log::error!("{}", gettext("Can not convert settings to JSON object."));
             return false;
         }
         let obj = obj.unwrap();
@@ -415,25 +415,25 @@ impl SettingStore {
             match remove_file(path) {
                 Ok(_) => {}
                 Err(e) => {
-                    println!("{} {}", gettext("Failed to remove file:"), e);
+                    log::error!("{} {}", gettext("Failed to remove file:"), e);
                     return false;
                 }
             }
         }
         let r = File::create(path);
         if r.is_err() {
-            println!("{} {}", gettext("Failed to create file:"), r.unwrap_err());
+            log::error!("{} {}", gettext("Failed to create file:"), r.unwrap_err());
             return false;
         }
         let mut f = r.unwrap();
         let r = f.write(s.as_bytes());
         if r.is_err() {
-            println!("{} {}", gettext("Failed to write file:"), r.unwrap_err());
+            log::error!("{} {}", gettext("Failed to write file:"), r.unwrap_err());
             return false;
         }
         let r = f.flush();
         if r.is_err() {
-            println!("{} {}", gettext("Failed to flush file:"), r.unwrap_err());
+            log::error!("{} {}", gettext("Failed to flush file:"), r.unwrap_err());
             return false;
         }
         true
diff --git a/src/settings_list.rs b/src/settings_list.rs
index 26b222d..03bbd37 100644
--- a/src/settings_list.rs
+++ b/src/settings_list.rs
@@ -82,7 +82,7 @@ fn check_cors_entries(obj: &JsonValue) -> bool {
     match parse_cors_entries(obj) {
         Ok(_) => true,
         Err(e) => {
-            println!("{}", e);
+            log::error!("{}", e);
             false
         }
     }
diff --git a/src/utils.rs b/src/utils.rs
index ba7b5b5..f919f47 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -49,14 +49,14 @@ pub fn ask_need_overwrite(path: &str) -> bool {
 pub fn get_file_name_from_url<U: IntoUrl>(url: U) -> Option<String> {
     let u = url.into_url();
     if u.is_err() {
-        println!("{} {}", gettext("Can not parse URL:"), u.unwrap_err());
+        log::error!("{} {}", gettext("Can not parse URL:"), u.unwrap_err());
         return None;
     }
     let u = u.unwrap();
     let path = Path::new(u.path());
     let re = path.file_name();
     if re.is_none() {
-        println!(
+        log::error!(
             "{} {}",
             gettext("Failed to get file name from path:"),
             u.path()
diff --git a/src/webclient.rs b/src/webclient.rs
index c1200a4..64cc178 100644
--- a/src/webclient.rs
+++ b/src/webclient.rs
@@ -177,12 +177,12 @@ impl WebClient {
                             self.get_cookies_as_mut().jar.get_mut().add(c);
                         }
                         None => {
-                            println!("{}", gettext("Failed to parse Set-Cookie header."));
+                            log::warn!("{}", gettext("Failed to parse Set-Cookie header."));
                         }
                     }
                 }
                 Err(e) => {
-                    println!("{} {}", gettext("Failed to convert to string:"), e);
+                    log::warn!("{} {}", gettext("Failed to convert to string:"), e);
                 }
             }
         }
@@ -237,7 +237,7 @@ impl WebClient {
     ) -> Option<Response> {
         let u = url.into_url();
         if u.is_err() {
-            println!("{} \"{}\"", gettext("Can not parse URL:"), u.unwrap_err());
+            log::error!("{} \"{}\"", gettext("Can not parse URL:"), u.unwrap_err());
             return None;
         }
         let mut u = u.unwrap();
@@ -247,7 +247,7 @@ impl WebClient {
         }
         let obj = obj.unwrap();
         if !obj.is_object() && !obj.is_array() {
-            println!(
+            log::error!(
                 "{} \"{}\"",
                 gettext("Parameters should be object or array:"),
                 obj
@@ -269,11 +269,11 @@ impl WebClient {
             } else {
                 for v in obj.members() {
                     if !v.is_object() {
-                        println!("{} \"{}\"", gettext("Parameters should be array:"), v);
+                        log::error!("{} \"{}\"", gettext("Parameters should be array:"), v);
                         return None;
                     }
                     if v.len() < 2 {
-                        println!("{} \"{}\"", gettext("Parameters need at least a value:"), v);
+                        log::error!("{} \"{}\"", gettext("Parameters need at least a value:"), v);
                         return None;
                     }
                     let okey = &v[0];
@@ -318,7 +318,7 @@ impl WebClient {
                 let t =
                     self.get_retry_interval().as_ref().unwrap()[(count - 1).try_into().unwrap()];
                 if !t.is_zero() {
-                    println!(
+                    log::info!(
                         "{}",
                         gettext("Retry after <num> seconds.")
                             .replace("<num>", format!("{}", t.as_secs_f64()).as_str())
@@ -327,7 +327,7 @@ impl WebClient {
                     tokio::time::sleep(t).await;
                 }
             }
-            println!(
+            log::info!(
                 "{}",
                 gettext("Retry <count> times now.")
                     .replace("<count>", format!("{}", count).as_str())
@@ -395,7 +395,7 @@ impl WebClient {
                 let t =
                     self.get_retry_interval().as_ref().unwrap()[(count - 1).try_into().unwrap()];
                 if !t.is_zero() {
-                    println!(
+                    log::info!(
                         "{}",
                         gettext("Retry after <num> seconds.")
                             .replace("<num>", format!("{}", t.as_secs_f64()).as_str())
@@ -404,7 +404,7 @@ impl WebClient {
                     tokio::time::sleep(t).await;
                 }
             }
-            println!(
+            log::info!(
                 "{}",
                 gettext("Retry <count> times now.")
                     .replace("<count>", format!("{}", count).as_str())