diff --git a/NanoID.cabal b/NanoID.cabal
--- a/NanoID.cabal
+++ b/NanoID.cabal
@@ -1,5 +1,5 @@
 name:                NanoID
-version:             1.0.1
+version:             1.2.0
 synopsis:            NanoID generator
 description:         Library and CLI tool for NanoID generation
 license:             BSD3
@@ -10,6 +10,7 @@
 category:            Data
 build-type:          Simple
 cabal-version:       >=1.10
+extra-source-files:  ReadMe.md
 
 Tested-With: GHC ==8.4.4 || ==8.6.5 || ==8.8.4 || ==8.10.1 || ==8.10.4 || ==9.0.1
 
@@ -19,7 +20,7 @@
 
 library
   exposed-modules:     Data.NanoID
-  build-depends:       base       >=4.7 && < 4.16
+  build-depends:       base       >= 4.7 && < 4.16
                      , bytestring >= 0.10 && < 0.12
                      , extra      >= 1.6 && < 1.8
                      , mwc-random >= 0.13 && < 0.16
@@ -29,7 +30,7 @@
 executable nanoid
   main-is:             Main.hs
   other-modules:       Options
-  build-depends:       base                 >=4.7 && < 4.16
+  build-depends:       base                 >= 4.7 && < 4.16
                      , bytestring           >= 0.10 && < 0.12
                      , mwc-random           >= 0.13 && < 0.16
                      , NanoID
diff --git a/ReadMe.md b/ReadMe.md
new file mode 100644
--- /dev/null
+++ b/ReadMe.md
@@ -0,0 +1,18 @@
+# NanoID generator, library and CLI tool [![Build Status](https://travis-ci.org/MichelBoucey/NanoID.svg?branch=main)](https://travis-ci.org/github/MichelBoucey/NanoID)
+
+```
+[user@box ~] $ nanoid -h
+nanoid v1.0.1, (c) Michel Boucey 2021
+
+Usage: nanoid [-a|--alphabet ARG] [-l|--length ARG] [-q|--quantity ARG] 
+              [-n|--newline]
+  NanoID generator
+
+Available options:
+  -a,--alphabet ARG        Use an alternative alphabet (ascii chars only)
+  -l,--length ARG          Get shorter NanoID
+  -q,--quantity ARG        Quantity of NanoID to generate
+  -n,--newline             Do not output the trailing newline
+  -h,--help                Show this help text
+```
+
diff --git a/app/Main.hs b/app/Main.hs
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -2,6 +2,7 @@
 
 import           Control.Monad
 import qualified Data.ByteString.Char8 as C
+import           Data.Either
 import           Options.Applicative
 import           System.Exit
 import           System.Random.MWC
@@ -17,8 +18,9 @@
     else do
       let alphabet' = Alphabet { unAlphabet = C.pack alphabet }
       replicateM_ quantity $
-        unNanoID <$> (createSystemRandom >>= customNanoID alphabet' length) >>= putNanoID newline
+        createSystemRandom >>= customNanoID alphabet' length >>= putNanoID newline
       exitSuccess
-      where
-        putNanoID n = if n then C.putStrLn else C.putStr
+        where
+          putNanoID nl = either (put nl . C.pack) (put nl . unNanoID)
+            where put nl = if nl then C.putStrLn else C.putStr
 
diff --git a/src/Data/NanoID.hs b/src/Data/NanoID.hs
--- a/src/Data/NanoID.hs
+++ b/src/Data/NanoID.hs
@@ -13,12 +13,15 @@
 defaultAlphabet :: Alphabet
 defaultAlphabet = Alphabet (C.pack "ABCDEFGHIJKLMNOPKRSTUVWXYZ_-abcdefghijklmnopqrstuvwxyz")
 
-nanoID :: IO NanoID
+nanoID :: IO (Either String NanoID)
 nanoID = createSystemRandom >>= customNanoID defaultAlphabet 21
 
-customNanoID :: Alphabet -> Length -> GenIO-> IO NanoID
-customNanoID a l g = do
-  let acs = unAlphabet a
-      al = C.length acs
-  NanoID . C.pack <$> replicateM l ((\r -> C.index acs (r-1)) <$> uniformR (1,al) g)
+customNanoID :: Alphabet -> Length -> GenIO-> IO (Either String NanoID)
+customNanoID a l g =
+  if l > 21
+    then return (Left "The length of NanoID is less or equal to 21")
+    else do
+      let acs = unAlphabet a
+          al = C.length acs
+      pure . NanoID . C.pack <$> replicateM l ((\r -> C.index acs (r-1)) <$> uniformR (1,al) g)