diff --git a/src/lib.rs b/src/lib.rs
index e03a68d..7370b02 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -36,10 +36,11 @@
 //! println!("RESULT = {:#?}", res);
 //! ```
 
+use thiserror::Error;
+
 #[cfg(feature = "embedded-server")]
 use crate::server::EmbeddedServer;
 use std::collections::HashMap;
-use std::error::Error;
 
 #[cfg(feature = "embedded-server")]
 pub mod server;
@@ -302,6 +303,28 @@ pub struct SuggestResult {
     pub suggestions: Vec<String>,
 }
 
+#[derive(Debug, Error)]
+pub enum Error {
+    #[cfg(feature = "embedded-server")]
+    #[error("Grammalecte-server failed to start")]
+    ServerStartFailed(#[from] server::Error),
+
+    #[error("Failed to Serialize Option in Json")]
+    OptionJsonSerialization(#[source] serde_json::Error),
+
+    #[error("Failed to send request `check with option`")]
+    RequestSendCheckWithOptions(#[source] reqwest::Error),
+
+    #[error("Failed to send request `suggest`")]
+    RequestSendSuggest(#[source] reqwest::Error),
+
+    #[error("Failed to Deserialize Check result")]
+    CheckResultDeserialize(#[source] reqwest::Error),
+
+    #[error("Failed to Deserialize Suggest result")]
+    SuggestDeserialize(#[source] reqwest::Error),
+}
+
 /// The Grammalecte client itself
 pub struct GrammalecteClient {
     base_url: String,
@@ -335,7 +358,7 @@ impl GrammalecteClient {
     ///
     /// Python 3.7 or higher must is required at runtime
     #[cfg(feature = "embedded-server")]
-    pub fn start_server() -> Result<Self, Box<dyn Error>> {
+    pub fn start_server() -> Result<Self, Error> {
         let server = EmbeddedServer::start()?;
         Ok(Self {
             base_url: server.base_url(),
@@ -344,7 +367,7 @@ impl GrammalecteClient {
     }
 
     /// Run spell check on text
-    pub async fn spell_check(&self, text: &str) -> Result<CheckResult, Box<dyn Error>> {
+    pub async fn spell_check(&self, text: &str) -> Result<CheckResult, Error> {
         self.spell_check_with_options(text, &HashMap::new()).await
     }
 
@@ -353,7 +376,7 @@ impl GrammalecteClient {
         &self,
         text: &str,
         options: &HashMap<GramOpt, bool>,
-    ) -> Result<CheckResult, Box<dyn Error>> {
+    ) -> Result<CheckResult, Error> {
         let url = format!("{}/gc_text/fr", self.base_url);
         log::debug!("Will use URL {} for spell check", url);
 
@@ -361,7 +384,7 @@ impl GrammalecteClient {
             .iter()
             .map(|t| (t.0.id(), t.1))
             .collect::<HashMap<_, _>>();
-        let options = serde_json::to_string(&options)?;
+        let options = serde_json::to_string(&options).map_err(Error::OptionJsonSerialization)?;
 
         let mut params = HashMap::new();
         params.insert("text", text);
@@ -371,15 +394,17 @@ impl GrammalecteClient {
             .post(url)
             .form(&params)
             .send()
-            .await?
+            .await
+            .map_err(Error::RequestSendCheckWithOptions)?
             .json::<CheckResult>()
-            .await?;
+            .await
+            .map_err(Error::CheckResultDeserialize)?;
 
         Ok(result)
     }
 
     /// Ask for word suggestion
-    pub async fn suggest(&self, token: &str) -> Result<SuggestResult, Box<dyn Error>> {
+    pub async fn suggest(&self, token: &str) -> Result<SuggestResult, Error> {
         let url = format!("{}/suggest/fr", self.base_url);
         log::debug!("Will use URL {} for word suggestion", url);
 
@@ -390,9 +415,11 @@ impl GrammalecteClient {
             .post(&url)
             .form(&params)
             .send()
-            .await?
+            .await
+            .map_err(Error::RequestSendSuggest)?
             .json()
-            .await?)
+            .await
+            .map_err(Error::SuggestDeserialize)?)
     }
 }
 
diff --git a/src/server.rs b/src/server.rs
index ea7f312..be2a881 100644
--- a/src/server.rs
+++ b/src/server.rs
@@ -1,10 +1,44 @@
 use crate::server::utils::{get_free_port, wait_for_port};
 use mktemp::Temp;
-use std::error::Error;
-use std::io::{Cursor, Read};
+use std::io::{self, Cursor, Read};
 use std::process::{Child, Stdio};
+use thiserror::Error;
+use zip::result::ZipError;
 use zip::ZipArchive;
 
+#[derive(Debug, Error)]
+pub enum Error {
+    #[error("Grammalecte-server failed to launch process")]
+    StartServerProcess(#[source] io::Error),
+
+    #[error("Failed to get free port")]
+    GetFreePort(#[source] io::Error),
+
+    #[error("Port {port} did not open in time!")]
+    WaitPortOpen { port: u16 },
+
+    #[error("Failed create temporary directory")]
+    CreateTempDir(#[source] io::Error),
+
+    #[error("TODO")]
+    ZipArchive(#[source] ZipError),
+
+    #[error("TODO")]
+    ZipFileIndex(#[source] ZipError),
+
+    // TODO: rename
+    #[error("TODO")]
+    CreateDirectory(#[source] io::Error),
+
+    // TODO: rename
+    #[error("TODO")]
+    ZipFileReadToEnd(#[source] io::Error),
+
+    // TODO: rename
+    #[error("TODO")]
+    WriteFile(#[source] io::Error),
+}
+
 pub struct EmbeddedServer {
     _srv_dir: Temp,
     port: u16,
@@ -13,29 +47,30 @@ pub struct EmbeddedServer {
 
 impl EmbeddedServer {
     /// Start embedded Grammalecte server on a random free port
-    pub fn start() -> Result<Self, Box<dyn Error>> {
-        Self::start_listen_on_port(get_free_port()?)
+    pub fn start() -> Result<Self, Error> {
+        Self::start_listen_on_port(get_free_port())
     }
 
     /// Start embedded Grammalecte server on a given port
-    pub fn start_listen_on_port(port: u16) -> Result<Self, Box<dyn Error>> {
+    pub fn start_listen_on_port(port: u16) -> Result<Self, Error> {
         log::info!("Will start server");
         // First, unpack server
-        let dest = mktemp::Temp::new_dir()?;
+        let dest = mktemp::Temp::new_dir().map_err(Error::CreateTempDir)?;
         let cursor = Cursor::new(include_bytes!("GrammalecteDist.zip"));
-        let mut zip = ZipArchive::new(cursor)?;
+        let mut zip = ZipArchive::new(cursor).map_err(Error::ZipArchive)?;
         for i in 0..zip.len() {
-            let mut file = zip.by_index(i)?;
+            let mut file = zip.by_index(i).map_err(Error::ZipFileIndex)?;
             if file.is_dir() {
                 log::debug!("Create directory: {}", file.name());
-                std::fs::create_dir_all(dest.join(file.name()))?;
+                std::fs::create_dir_all(dest.join(file.name())).map_err(Error::CreateDirectory)?;
             } else {
                 log::debug!("Decompress file: {}", file.name());
 
                 let mut buff = Vec::with_capacity(file.size() as usize);
-                file.read_to_end(&mut buff)?;
+                file.read_to_end(&mut buff)
+                    .map_err(Error::ZipFileReadToEnd)?;
 
-                std::fs::write(dest.join(file.name()), buff)?;
+                std::fs::write(dest.join(file.name()), buff).map_err(Error::WriteFile)?;
             }
         }
 
@@ -54,7 +89,8 @@ impl EmbeddedServer {
             .arg(port.to_string())
             .stdout(Stdio::null())
             .stderr(Stdio::null())
-            .spawn()?;
+            .spawn()
+            .map_err(Error::StartServerProcess)?;
 
         wait_for_port(port)?;
 
@@ -78,11 +114,12 @@ impl Drop for EmbeddedServer {
 }
 
 mod utils {
-    use std::io::ErrorKind;
     use std::time::Duration;
 
+    use super::Error;
+
     /// Get a free port
-    pub fn get_free_port() -> std::io::Result<u16> {
+    pub fn get_free_port() -> u16 {
         let mut port = 0;
 
         while !(2000..=64000).contains(&port) {
@@ -93,10 +130,10 @@ mod utils {
             port += 1;
         }
 
-        Ok(port)
+        port
     }
 
-    pub fn wait_for_port(port: u16) -> std::io::Result<()> {
+    pub fn wait_for_port(port: u16) -> Result<(), Error> {
         for _ in 0..50 {
             if port_scanner::scan_port(port) {
                 return Ok(());
@@ -104,9 +141,6 @@ mod utils {
             std::thread::sleep(Duration::from_millis(100));
         }
 
-        Err(std::io::Error::new(
-            ErrorKind::Other,
-            format!("Port {} did not open in time!", port),
-        ))?
+        Err(Error::WaitPortOpen { port })
     }
 }