diff --git a/src/core/lib/Base45.mjs b/src/core/lib/Base45.mjs
new file mode 100644
index 00000000..d3e279fa
--- /dev/null
+++ b/src/core/lib/Base45.mjs
@@ -0,0 +1,27 @@
+/**
+ * Base45 resources.
+ *
+ * @author Thomas Weißschuh [thomas@t-8ch.de]
+ * @copyright Crown Copyright 2021
+ * @license Apache-2.0
+ */
+
+/**
+ * Highlight to Base45
+ */
+export function highlightToBase45(pos, args) {
+    pos[0].start = Math.floor(pos[0].start / 2) * 3;
+    pos[0].end = Math.ceil(pos[0].end / 2) * 3;
+    return pos;
+}
+
+/**
+ * Highlight from Base45
+ */
+export function highlightFromBase45(pos, args) {
+    pos[0].start = Math.floor(pos[0].start / 3) * 2;
+    pos[0].end = Math.ceil(pos[0].end / 3) * 2;
+    return pos;
+}
+
+export const ALPHABET = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:";
diff --git a/src/core/operations/FromBase45.mjs b/src/core/operations/FromBase45.mjs
index 8e78ed0c..890d35d6 100644
--- a/src/core/operations/FromBase45.mjs
+++ b/src/core/operations/FromBase45.mjs
@@ -4,6 +4,7 @@
  * @license Apache-2.0
  */
 
+import {ALPHABET, highlightToBase45, highlightFromBase45} from "../lib/Base45.mjs";
 import Operation from "../Operation.mjs";
 import OperationError from "../errors/OperationError.mjs";
 import Utils from "../Utils.mjs";
@@ -26,6 +27,9 @@ class FromBase45 extends Operation {
         this.infoURL = "https://wikipedia.org/wiki/List_of_numeral_systems";
         this.inputType = "string";
         this.outputType = "byteArray";
+
+        this.highlight = highlightFromBase45;
+        this.highlightReverse = highlightToBase45;
     }
 
     /**
@@ -34,7 +38,6 @@ class FromBase45 extends Operation {
      * @returns {byteArray}
      */
     run(input, args) {
-        const alphabet = Utils.expandAlphRange("0-9A-Z $%*+-./:").join("");
         if (!input) return [];
 
         const res = [];
@@ -43,7 +46,7 @@ class FromBase45 extends Operation {
             triple.reverse();
             let b = 0;
             for (const c of triple) {
-                const idx = alphabet.indexOf(c);
+                const idx = ALPHABET.indexOf(c);
                 if (idx === -1) {
                     throw new OperationError(`Character not in alphabet: '${c}'`);
                 }
diff --git a/src/core/operations/ToBase45.mjs b/src/core/operations/ToBase45.mjs
index 019c3dd9..d7455dca 100644
--- a/src/core/operations/ToBase45.mjs
+++ b/src/core/operations/ToBase45.mjs
@@ -4,6 +4,7 @@
  * @license Apache-2.0
  */
 
+import {ALPHABET, highlightToBase45, highlightFromBase45} from "../lib/Base45.mjs";
 import Operation from "../Operation.mjs";
 import Utils from "../Utils.mjs";
 
@@ -31,6 +32,9 @@ class ToBase45 extends Operation {
                 value: "0-9A-Za-z"
             }
         ];
+
+        this.highlight = highlightToBase45;
+        this.highlightReverse = highlightFromBase45;
     }
 
     /**
@@ -39,7 +43,6 @@ class ToBase45 extends Operation {
      * @returns {string}
      */
     run(input, args) {
-        const alphabet = Utils.expandAlphRange("0-9A-Z $%*+-./:").join("");
         input = new Uint8Array(input);
         if (!input) return "";
 
@@ -54,7 +57,7 @@ class ToBase45 extends Operation {
 
             let chars = 0;
             do {
-                res.push(alphabet[b % 45]);
+                res.push(ALPHABET[b % 45]);
                 chars++;
                 b = Math.floor(b / 45);
             } while (b > 0);