diff --git a/CONFIGURATION.md b/CONFIGURATION.md
index c264fad..35e188d 100644
--- a/CONFIGURATION.md
+++ b/CONFIGURATION.md
@@ -18,6 +18,11 @@ Address to listen for connections on in the format of `interface:port`.
 
 `:1965`
 
+## Types
+
+Content types may be defined by file extension. When a type is not defined for
+the requested file extension, content type is detected automatically.
+
 ## Hosts
 
 Hosts are defined by their hostname followed by one or more paths to serve.
@@ -181,6 +186,10 @@ References:
 # Address to listen on
 listen: :1965
 
+# Custom content types
+types:
+  .json: application/json; charset=UTF-8
+
 # Hosts and paths to serve
 hosts:
   default: # Default host configuration
diff --git a/config.go b/config.go
index 018ddc4..87a6e8e 100644
--- a/config.go
+++ b/config.go
@@ -68,6 +68,8 @@ type hostConfig struct {
 type serverConfig struct {
 	Listen string
 
+	Types map[string]string
+
 	Hosts map[string]*hostConfig
 
 	DisableSize bool
@@ -108,6 +110,10 @@ func readconfig(configPath string) error {
 		log.Fatal("listen address must be specified")
 	}
 
+	if config.Types == nil {
+		config.Types = make(map[string]string)
+	}
+
 	if config.SaneEOL {
 		newLine = "\n"
 	} else {
@@ -126,6 +132,20 @@ func readconfig(configPath string) error {
 		}
 	}
 
+	// Default content types
+	if config.Types[".htm"] == "" {
+		config.Types[".htm"] = htmlType
+	}
+	if config.Types[".html"] == "" {
+		config.Types[".html"] = htmlType
+	}
+	if config.Types[".gmi"] == "" {
+		config.Types[".gmi"] = geminiType
+	}
+	if config.Types[".gemini"] == "" {
+		config.Types[".gemini"] = geminiType
+	}
+
 	defaultHost := config.Hosts["default"]
 	delete(config.Hosts, "default")
 
diff --git a/serve_file.go b/serve_file.go
index 2771d22..9dd738b 100644
--- a/serve_file.go
+++ b/serve_file.go
@@ -8,7 +8,6 @@ import (
 	"os"
 	"path/filepath"
 	"sort"
-	"strings"
 
 	"github.com/h2non/filetype"
 )
@@ -98,33 +97,35 @@ func serveFile(c net.Conn, serve *pathConfig, filePath string) {
 	file, _ := os.Open(filePath)
 	defer file.Close()
 
-	// Read file header
-	buf := make([]byte, 261)
-	n, _ := file.Read(buf)
-
-	// Write response header
-	var contentType string
-	if strings.HasSuffix(filePath, ".html") && strings.HasSuffix(filePath, ".htm") {
-		contentType = "text/html; charset=utf-8"
-	} else if strings.HasSuffix(filePath, ".txt") && strings.HasSuffix(filePath, ".text") {
-		contentType = "text/plain; charset=utf-8"
-	} else if !strings.HasSuffix(filePath, ".gmi") && !strings.HasSuffix(filePath, ".gemini") {
-		kind, _ := filetype.Match(buf[:n])
-		if kind != filetype.Unknown {
+	// Read content type
+	var (
+		buf = make([]byte, 261)
+		n   int
+	)
+	contentType := config.Types[filepath.Ext(filePath)]
+	if contentType == "" {
+		n, _ = file.Read(buf)
+		kind, err := filetype.Match(buf[:n])
+		if err == nil && kind != filetype.Unknown && kind.MIME.Value != "" {
 			contentType = kind.MIME.Value
+		} else {
+			contentType = plainType
 		}
 	}
-	if contentType == "" {
-		contentType = geminiType
-	}
+
+	// Read file size
 	size := int64(-1)
 	info, err := file.Stat()
 	if err == nil {
 		size = info.Size()
 	}
+
+	// Write response header
 	writeSuccess(c, serve, contentType, size)
 
-	// Write body
-	c.Write(buf[:n])
+	// Write file contents
+	if n > 0 {
+		c.Write(buf[:n])
+	}
 	io.Copy(c, file)
 }
diff --git a/server.go b/server.go
index 28426c0..6cda9af 100644
--- a/server.go
+++ b/server.go
@@ -24,7 +24,9 @@ const (
 
 	urlMaxLength = 1024
 
+	plainType  = "text/plain; charset=utf-8"
 	geminiType = "text/gemini; charset=utf-8"
+	htmlType   = "text/html; charset=utf-8"
 
 	logTimeFormat = "2006-01-02 15:04:05"
 )