diff --git a/Cargo.lock b/Cargo.lock
index 913f89a..6fb7915 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -282,7 +282,7 @@ dependencies = [
 
 [[package]]
 name = "jsonformat"
-version = "0.1.0"
+version = "1.0.0"
 dependencies = [
  "clap 3.0.0-beta.2",
  "criterion",
diff --git a/Cargo.toml b/Cargo.toml
index dd5b306..fbc3d87 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "jsonformat"
-version = "0.1.0"
+version = "1.0.0"
 authors = ["Nilstrieb <nilstrieb@gmail.com>"]
 edition = "2018"
 license = "MIT"
diff --git a/benches/bench.rs b/benches/bench.rs
index 5bd3956..002aa06 100644
--- a/benches/bench.rs
+++ b/benches/bench.rs
@@ -1,10 +1,10 @@
 use criterion::{criterion_group, criterion_main, Criterion};
-use jsonformat::format_json;
+use jsonformat::{format_json, Indentation};
 use std::{fs, io};
 
 /// You need a json file called massive.json in your project root
 fn format_massive_json(file: &str) -> io::Result<String> {
-    Ok(format_json(&file, None))
+    Ok(format_json(&file, Indentation::Default))
 }
 
 fn criterion_benchmark(c: &mut Criterion) {
diff --git a/src/lib.rs b/src/lib.rs
index 22e4aab..13f0612 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,13 +1,31 @@
+//!
+//! jsonformat is a library for formatting json.
+//!
+//! It does not do anything more than that, which makes it so fast.
+
+///
+/// Set the indentation used for the formatting.
+///
+/// Note: It is *not* recommended to set indentation to anything oder than some spaces or some tabs,
+/// but nothing is stopping you from doing that.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+pub enum Indentation<'a> {
+    /// Use the default indentation, which is two spaces
+    Default,
+    /// Use a custom indentation String
+    Custom(&'a str),
+}
+
 ///
 /// # Formats a json string
 ///
-/// The indentation can be set to any custom value  
+/// The indentation can be set to any value using [Indentation](jsonformat::Indentation)
 /// The default value is two spaces
 /// The default indentation is faster than a custom one
 ///
-pub fn format_json(json: &str, indentation: Option<&str>) -> String {
+pub fn format_json(json: &str, indentation: Indentation) -> String {
     // at least as big as the input to avoid resizing
-    // this might be too big if the input string is formatted in a weird way, but that's not expected
+    // this might be too big if the input string is formatted in a weird way, but that's not expected, and it will still be efficient
     let mut out = String::with_capacity(json.len());
 
     let mut escaped = false;
@@ -86,14 +104,14 @@ pub fn format_json(json: &str, indentation: Option<&str>) -> String {
     out
 }
 
-fn indent(buf: &mut String, level: usize, indent_str: Option<&str>) {
+fn indent(buf: &mut String, level: usize, indent_str: Indentation) {
     for _ in 0..level {
         match indent_str {
-            None => {
+            Indentation::Default => {
                 buf.push(' ');
                 buf.push(' ');
             }
-            Some(indent) => {
+            Indentation::Custom(indent) => {
                 buf.push_str(indent);
             }
         }
@@ -107,27 +125,27 @@ mod test {
     #[test]
     fn echoes_primitive() {
         let json = "1.35";
-        assert_eq!(json, format_json(json, None));
+        assert_eq!(json, format_json(json, Indentation::Default));
     }
 
     #[test]
     fn ignore_whitespace_in_string() {
         let json = "\" hallo \"";
-        assert_eq!(json, format_json(json, None));
+        assert_eq!(json, format_json(json, Indentation::Default));
     }
 
     #[test]
     fn remove_leading_whitespace() {
         let json = "   0";
         let expected = "0";
-        assert_eq!(expected, format_json(json, None));
+        assert_eq!(expected, format_json(json, Indentation::Default));
     }
 
     #[test]
     fn handle_escaped_strings() {
         let json = "  \" hallo \\\" \" ";
         let expected = "\" hallo \\\" \"";
-        assert_eq!(expected, format_json(json, None));
+        assert_eq!(expected, format_json(json, Indentation::Default));
     }
 
     #[test]
@@ -136,7 +154,7 @@ mod test {
         let expected = "{
   \"a\": 0
 }";
-        assert_eq!(expected, format_json(json, None));
+        assert_eq!(expected, format_json(json, Indentation::Default));
     }
 
     #[test]
@@ -147,7 +165,7 @@ mod test {
   2,
   null
 ]";
-        assert_eq!(expected, format_json(json, None));
+        assert_eq!(expected, format_json(json, Indentation::Default));
     }
 
     #[test]
@@ -163,7 +181,7 @@ mod test {
   }
 ]";
 
-        assert_eq!(expected, format_json(json, None));
+        assert_eq!(expected, format_json(json, Indentation::Default));
     }
 
     #[test]
@@ -178,6 +196,6 @@ mod test {
   }
 ]";
 
-        assert_eq!(expected, format_json(expected, None));
+        assert_eq!(expected, format_json(expected, Indentation::Default));
     }
 }
diff --git a/src/main.rs b/src/main.rs
index 501a4c7..238950f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,5 +1,5 @@
 use clap::clap_app;
-use jsonformat::format_json;
+use jsonformat::{format_json, Indentation};
 use std::fs;
 use std::io;
 use std::io::Read;
@@ -36,7 +36,12 @@ fn main() -> Result<(), io::Error> {
             .replace("t", "\t")
     });
 
-    let formatted = format_json(&str, replaced_indent.as_deref());
+    let indent = match replaced_indent {
+        Some(ref str) => Indentation::Custom(str),
+        None => Indentation::Default,
+    };
+
+    let formatted = format_json(&str, indent);
 
     let mut output = matches.value_of("output");
     let mut windows_output_default_file: Option<String> = None;