diff --git a/src/main.rs b/src/main.rs
index 3fd4fe4..cbac36d 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -8,33 +8,26 @@ extern crate rand;
 extern crate reqwest;
 #[macro_use]
 extern crate serde_derive;
-extern crate serde_json;
 extern crate sha2;
 
 mod b64;
+mod metadata;
 mod reader;
 
-use std::fmt;
 use std::fs::File;
 use std::io::BufReader;
 use std::path::Path;
 
 use clap::{App, Arg};
 use hkdf::Hkdf;
-use hyper::error::Error as HyperError;
-use mime_guess::Mime;
 use openssl::symm::{Cipher, encrypt_aead};
 use rand::{Rng, thread_rng};
-use reqwest::header::{
-    Authorization,
-    Formatter as HeaderFormatter,
-    Header,
-    Raw
-};
+use reqwest::header::Authorization;
 use reqwest::mime::APPLICATION_OCTET_STREAM;
 use reqwest::multipart::Part;
 use sha2::Sha256;
 
+use metadata::{Metadata, XFileMetadata};
 use reader::EncryptedFileReaderTagged;
 
 fn main() {
@@ -188,77 +181,6 @@ fn derive_meta_key(secret: &[u8]) -> Vec<u8> {
     hkdf(16, secret, Some(b"metadata"))
 }
 
-/// File metadata, which is send to the server.
-#[derive(Serialize)]
-struct Metadata {
-    /// The input vector.
-    iv: String,
-
-    /// The file name.
-    name: String,
-
-    /// The file mimetype.
-    #[serde(rename="type")]
-    mime: String,
-}
-
-impl Metadata {
-    /// Construct metadata from the given properties.
-    ///
-    /// Parameters:
-    /// * iv: initialisation vector
-    /// * name: file name
-    /// * mime: file mimetype
-    pub fn from(iv: &[u8], name: String, mime: Mime) -> Self {
-        Metadata {
-            iv: base64_encode(iv),
-            name,
-            mime: mime.to_string(),
-        }
-    }
-
-    /// Convert this structure to a JSON string.
-    pub fn to_json(&self) -> String {
-        serde_json::to_string(&self).unwrap()
-    }
-}
-
-/// A X-File-Metadata header for reqwest, that is used to pass encrypted
-/// metadata to the server.
-///
-/// The encrypted metadata (bytes) is base64 encoded when constructing this
-/// header using `from`.
-#[derive(Clone)]
-struct XFileMetadata {
-    /// The metadata, as a base64 encoded string.
-    metadata: String,
-}
-
-impl XFileMetadata {
-    /// Construct the header from the given encrypted metadata.
-    pub fn from(bytes: &[u8]) -> Self {
-        XFileMetadata {
-            metadata: base64_encode(bytes),
-        }
-    }
-}
-
-impl Header for XFileMetadata {
-    fn header_name() -> &'static str {
-        "X-File-Metadata"
-    }
-
-    fn parse_header(_raw: &Raw) -> Result<Self, HyperError> {
-        // TODO: implement this some time
-        unimplemented!();
-    }
-
-    fn fmt_header(&self, f: &mut HeaderFormatter) -> fmt::Result {
-        // TODO: is this encoding base64 for us?
-        f.fmt_line(&self.metadata)
-    }
-}
-
 /// The response from the server after a file has been uploaded.
 /// This response contains the file ID and owner key, to manage the file.
 ///
diff --git a/src/metadata.rs b/src/metadata.rs
new file mode 100644
index 0000000..1443110
--- /dev/null
+++ b/src/metadata.rs
@@ -0,0 +1,85 @@
+extern crate serde_json;
+
+use std::fmt;
+
+use hyper::error::Error as HyperError;
+use mime_guess::Mime;
+use reqwest::header::{
+    Formatter as HeaderFormatter,
+    Header,
+    Raw,
+};
+
+use b64;
+
+/// File metadata, which is send to the server.
+#[derive(Serialize)]
+pub struct Metadata {
+    /// The input vector.
+    iv: String,
+
+    /// The file name.
+    name: String,
+
+    /// The file mimetype.
+    #[serde(rename="type")]
+    mime: String,
+}
+
+impl Metadata {
+    /// Construct metadata from the given properties.
+    ///
+    /// Parameters:
+    /// * iv: initialisation vector
+    /// * name: file name
+    /// * mime: file mimetype
+    pub fn from(iv: &[u8], name: String, mime: Mime) -> Self {
+        Metadata {
+            iv: b64::encode(iv),
+            name,
+            mime: mime.to_string(),
+        }
+    }
+
+    /// Convert this structure to a JSON string.
+    pub fn to_json(&self) -> String {
+        serde_json::to_string(&self).unwrap()
+    }
+}
+
+/// A X-File-Metadata header for reqwest, that is used to pass encrypted
+/// metadata to the server.
+///
+/// The encrypted metadata (bytes) is base64 encoded when constructing this
+/// header using `from`.
+#[derive(Clone)]
+pub struct XFileMetadata {
+    /// The metadata, as a base64 encoded string.
+    metadata: String,
+}
+
+impl XFileMetadata {
+    /// Construct the header from the given encrypted metadata.
+    pub fn from(bytes: &[u8]) -> Self {
+        XFileMetadata {
+            metadata: b64::encode(bytes),
+        }
+    }
+}
+
+/// Make this struct usable as reqwest header.
+impl Header for XFileMetadata {
+    fn header_name() -> &'static str {
+        "X-File-Metadata"
+    }
+
+    fn parse_header(_raw: &Raw) -> Result<Self, HyperError> {
+        // TODO: implement this some time
+        unimplemented!();
+    }
+
+    fn fmt_header(&self, f: &mut HeaderFormatter) -> fmt::Result {
+        // TODO: is this encoding base64 for us?
+        f.fmt_line(&self.metadata)
+    }
+}