diff --git a/Cargo.toml b/Cargo.toml
index 9f77ac8..2e4b40a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,6 +14,7 @@ keywords = ["cli"]
 
 [dependencies]
 anyhow = "1.0.83"
+base64 = "0.22.1"
 clap = { version = "4.5.4", features = ["derive"] }
 clap-num = "1.1.1"
 
diff --git a/src/format.rs b/src/format.rs
index baaea0b..909af1e 100644
--- a/src/format.rs
+++ b/src/format.rs
@@ -1,3 +1,5 @@
+use base64::prelude::*;
+
 pub type Num = u128;
 
 #[derive(Copy, Clone, Debug)]
@@ -6,15 +8,23 @@ pub enum Format {
     Hex,
     Bin,
     Octal,
+    Base64,
 }
 
 impl Format {
     pub fn prefix(&self) -> String {
         match self {
+            // apperently used nowhere, sometimes 0 is used as a prefix but I
+            // think this makes it more clear that this is decimal
             Format::Dec => "0d",
+            // very common
             Format::Hex => "0x",
+            // very common
             Format::Bin => "0b",
+            // somewhat common
             Format::Octal => "0o",
+            // perl and a few other programs seem to use this too
+            Format::Base64 => "0s",
         }
         .to_string()
     }
@@ -36,7 +46,20 @@ impl Format {
             Format::Dec => {
                 buf += &format!("{num}");
             }
+            Format::Base64 => buf += &BASE64_STANDARD.encode(u128_to_u8_slice(num)),
         }
         buf
     }
 }
+
+fn u128_to_u8_slice(mut num: u128) -> Vec<u8> {
+    if num == 0 {
+        return vec![0];
+    }
+    let mut buf: Vec<u8> = Vec::new();
+    while num > 0 {
+        buf.push(num as u8);
+        num >>= 8;
+    }
+    buf
+}
diff --git a/src/main.rs b/src/main.rs
index 7f5595e..babac9e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -13,7 +13,7 @@ use format::*;
 #[clap(author, version, about, long_about = None)]
 #[clap(group(
             ArgGroup::new("format")
-                .args(&["hex", "bin", "oct", "dec"]),
+                .args(&["hex", "bin", "oct", "dec", "base64"]),
         ))]
 struct Cli {
     #[arg(short, long)]
@@ -31,6 +31,9 @@ struct Cli {
     #[arg(short, long)]
     /// format to octal
     oct: bool,
+    #[arg(short = 's', long)]
+    /// format to base64
+    base64: bool,
     #[clap(value_parser=maybe_hex::<Num>, required=true)]
     /// at least one number that should be formatted
     ///
@@ -46,6 +49,8 @@ impl Cli {
             Format::Bin
         } else if self.dec {
             Format::Dec
+        } else if self.base64 {
+            Format::Base64
         } else if self.hex {
             Format::Hex
         } else {