diff --git a/Cargo.toml b/Cargo.toml
index c213679..fbe7c5e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -52,6 +52,7 @@ bytes = "1.2.0"
 quinn = { version = "0.8.3", optional = true }
 h3 = { git = "https://github.com/hyperium/h3.git", optional = true }
 h3-quinn = { git = "https://github.com/hyperium/h3.git", optional = true }
+thiserror = "1.0.31"
 
 
 [target.'cfg(not(target_env = "msvc"))'.dependencies]
diff --git a/src/backend_opt.rs b/src/backend_opt.rs
index e40edc7..8774733 100644
--- a/src/backend_opt.rs
+++ b/src/backend_opt.rs
@@ -7,12 +7,12 @@ pub enum UpstreamOption {
   // TODO: Adds more options for heder override
 }
 impl TryFrom<&str> for UpstreamOption {
-  type Error = anyhow::Error;
+  type Error = RpxyError;
   fn try_from(val: &str) -> Result<Self> {
     match val {
       "override_host" => Ok(Self::OverrideHost),
       "upgrade_insecure_requests" => Ok(Self::UpgradeInsecureRequests),
-      _ => Err(anyhow!("Unsupported header option")),
+      _ => Err(RpxyError::Other(anyhow!("Unsupported header option"))),
     }
   }
 }
diff --git a/src/config/parse.rs b/src/config/parse.rs
index 0bb3f4d..4fe244e 100644
--- a/src/config/parse.rs
+++ b/src/config/parse.rs
@@ -14,7 +14,7 @@ use std::net::SocketAddr;
 // #[cfg(feature = "tls")]
 use std::path::PathBuf;
 
-pub fn parse_opts(globals: &mut Globals) -> Result<()> {
+pub fn parse_opts(globals: &mut Globals) -> std::result::Result<(), anyhow::Error> {
   let _ = include_str!("../../Cargo.toml");
   let options = clap::command!().arg(
     Arg::new("config_file")
@@ -191,7 +191,7 @@ pub fn parse_opts(globals: &mut Globals) -> Result<()> {
   Ok(())
 }
 
-fn get_reverse_proxy(rp_settings: &[ReverseProxyOption]) -> Result<ReverseProxy> {
+fn get_reverse_proxy(rp_settings: &[ReverseProxyOption]) -> std::result::Result<ReverseProxy, anyhow::Error> {
   let mut upstream: HashMap<PathNameLC, UpstreamGroup> = HashMap::default();
   rp_settings.iter().for_each(|rpo| {
     let path = match &rpo.path {
diff --git a/src/config/toml.rs b/src/config/toml.rs
index 90a1961..5f31ba6 100644
--- a/src/config/toml.rs
+++ b/src/config/toml.rs
@@ -78,7 +78,7 @@ impl UpstreamParams {
 }
 
 impl ConfigToml {
-  pub fn new(config_file: &str) -> Result<Self> {
+  pub fn new(config_file: &str) -> std::result::Result<Self, anyhow::Error> {
     let config_str = fs::read_to_string(config_file).context("Failed to read config file")?;
 
     toml::from_str(&config_str).context("Failed to parse toml config")
diff --git a/src/error.rs b/src/error.rs
index 4b30b2d..4e55bfb 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -1,12 +1,42 @@
-pub use anyhow::{anyhow, bail, ensure, Context, Result};
-// use thiserror::Error;
+pub use anyhow::{anyhow, bail, ensure, Context};
+use std::io;
+use thiserror::Error;
 
-// #[allow(clippy::enum_variant_names)]
-// #[derive(Debug, Error)]
-// pub enum RpxyError {
-//   // IoError,
-//   #[error("ConfigError: {0}")]
-//   ConfigError(String),
-//   // ConnectionError,
-//   // HttpError,
-// }
+pub type Result<T> = std::result::Result<T, RpxyError>;
+
+/// Describes things that can go wrong in the Rpxy
+#[derive(Debug, Error)]
+pub enum RpxyError {
+  #[error("Http Message Handler Error: {0}")]
+  Handler(&'static str),
+
+  #[error("Http Request Message Error: {0}")]
+  Request(&'static str),
+
+  #[error("I/O Error")]
+  Io(#[from] io::Error),
+
+  #[error("Quic Connection Error")]
+  QuicConn(#[from] quinn::ConnectionError),
+
+  #[error("H3 Error")]
+  H3(#[from] h3::Error),
+
+  #[error("rustls Connection Error")]
+  Rustls(#[from] rustls::Error),
+
+  #[error("Hyper Error")]
+  Hyper(#[from] hyper::Error),
+
+  #[error("Hyper Http Error")]
+  HyperHttp(#[from] hyper::http::Error),
+
+  #[error("Hyper Http HeaderValue Error")]
+  HyperHeaderValue(#[from] hyper::header::InvalidHeaderValue),
+
+  #[error("Hyper Http HeaderName Error")]
+  HyperHeaderName(#[from] hyper::header::InvalidHeaderName),
+
+  #[error(transparent)]
+  Other(#[from] anyhow::Error),
+}
diff --git a/src/handler/handler_main.rs b/src/handler/handler_main.rs
index 615e479..b85eb55 100644
--- a/src/handler/handler_main.rs
+++ b/src/handler/handler_main.rs
@@ -263,7 +263,9 @@ where
     apply_upstream_options_to_header(headers, client_addr, upstream_group, &upstream_chosen.uri)?;
 
     // update uri in request
-    ensure!(upstream_chosen.uri.authority().is_some() && upstream_chosen.uri.scheme().is_some());
+    if !(upstream_chosen.uri.authority().is_some() && upstream_chosen.uri.scheme().is_some()) {
+      return Err(RpxyError::Handler("Upstream uri `scheme` and `authority` is broken"));
+    };
     let new_uri = Uri::builder()
       .scheme(upstream_chosen.uri.scheme().unwrap().as_str())
       .authority(upstream_chosen.uri.authority().unwrap().as_str());
@@ -277,7 +279,9 @@ where
     let new_pq = match &upstream_group.replace_path {
       Some(new_path) => {
         let matched_path: &[u8] = upstream_group.path.as_ref();
-        ensure!(!matched_path.is_empty() && org_pq.len() >= matched_path.len());
+        if matched_path.is_empty() || org_pq.len() < matched_path.len() {
+          return Err(RpxyError::Handler("Upstream uri `path and query` is broken"));
+        };
         let mut new_pq = Vec::<u8>::with_capacity(org_pq.len() - matched_path.len() + new_path.len());
         new_pq.extend_from_slice(new_path);
         new_pq.extend_from_slice(&org_pq[matched_path.len()..]);
diff --git a/src/handler/utils_request.rs b/src/handler/utils_request.rs
index 1a131c6..9ff480d 100644
--- a/src/handler/utils_request.rs
+++ b/src/handler/utils_request.rs
@@ -63,10 +63,9 @@ impl<B> ParseHost for Request<B> {
     let uri_host = self.uri().host();
     // let uri_port = self.uri().port_u16();
 
-    ensure!(
-      !(headers_host.is_none() && uri_host.is_none()),
-      "No host in request header"
-    );
+    if !(!(headers_host.is_none() && uri_host.is_none())) {
+      return Err(RpxyError::Request("No host in request header"));
+    }
 
     // prioritize server_name in uri
     uri_host.map_or_else(
@@ -75,8 +74,8 @@ impl<B> ParseHost for Request<B> {
         if m.starts_with(&[b'[']) {
           // v6 address with bracket case. if port is specified, always it is in this case.
           let mut iter = m.split(|ptr| ptr == &b'[' || ptr == &b']');
-          iter.next().ok_or_else(|| anyhow!("Invalid Host"))?; // first item is always blank
-          iter.next().ok_or_else(|| anyhow!("Invalid Host"))
+          iter.next().ok_or(RpxyError::Request("Invalid Host"))?; // first item is always blank
+          iter.next().ok_or(RpxyError::Request("Invalid Host"))
         } else if m.len() - m.split(|v| v == &b':').fold(0, |acc, s| acc + s.len()) >= 2 {
           // v6 address case, if 2 or more ':' is contained
           Ok(m)
@@ -85,7 +84,7 @@ impl<B> ParseHost for Request<B> {
           m.split(|colon| colon == &b':')
             .into_iter()
             .next()
-            .ok_or_else(|| anyhow!("Invalid Host"))
+            .ok_or(RpxyError::Request("Invalid Host"))
         }
       },
       |v| Ok(v.as_bytes()),
diff --git a/src/proxy/proxy_h3.rs b/src/proxy/proxy_h3.rs
index 9cfd494..5892b1d 100644
--- a/src/proxy/proxy_h3.rs
+++ b/src/proxy/proxy_h3.rs
@@ -56,7 +56,7 @@ where
       }
       Err(err) => {
         warn!("QUIC accepting connection failed: {:?}", err);
-        return Err(anyhow!("{}", err));
+        return Err(RpxyError::QuicConn(err));
       }
     }
 
@@ -104,7 +104,7 @@ where
         debug!("HTTP/3 incoming request trailers");
         sender.send_trailers(trailers.unwrap()).await?;
       }
-      Ok(()) as Result<()>
+      Ok(())
     });
 
     let new_req: Request<Body> = Request::from_parts(req_parts, req_body);