diff --git a/src/core/operations/Bzip2Decompress.mjs b/src/core/operations/Bzip2Decompress.mjs
new file mode 100644
index 00000000..e31b3d2c
--- /dev/null
+++ b/src/core/operations/Bzip2Decompress.mjs
@@ -0,0 +1,55 @@
+/**
+ * @author n1474335 [n1474335@gmail.com]
+ * @copyright Crown Copyright 2016
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation";
+import bzip2 from "../vendor/bzip2.js";
+import OperationError from "../errors/OperationError";
+
+/**
+ * Bzip2 Decompress operation
+ */
+class Bzip2Decompress extends Operation {
+
+    /**
+     * Bzip2Decompress constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Bzip2 Decompress";
+        this.module = "Compression";
+        this.description = "Decompresses data using the Bzip2 algorithm.";
+        this.inputType = "byteArray";
+        this.outputType = "string";
+        this.args = [];
+        this.patterns = [
+            {
+                "match": "^\\x42\\x5a\\x68",
+                "flags": "",
+                "args": []
+            }
+        ];
+    }
+
+    /**
+     * @param {byteArray} input
+     * @param {Object[]} args
+     * @returns {string}
+     */
+    run(input, args) {
+        const compressed = new Uint8Array(input);
+
+        try {
+            const bzip2Reader = bzip2.array(compressed);
+            return bzip2.simple(bzip2Reader);
+        } catch (err) {
+            throw new OperationError(err);
+        }
+    }
+
+}
+
+export default Bzip2Decompress;
diff --git a/src/core/operations/Diff.mjs b/src/core/operations/Diff.mjs
new file mode 100644
index 00000000..6627cf6e
--- /dev/null
+++ b/src/core/operations/Diff.mjs
@@ -0,0 +1,124 @@
+/**
+ * @author n1474335 [n1474335@gmail.com]
+ * @copyright Crown Copyright 2016
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation";
+import Utils from "../Utils";
+import * as JsDiff from "diff";
+import OperationError from "../errors/OperationError";
+
+/**
+ * Diff operation
+ */
+class Diff extends Operation {
+
+    /**
+     * Diff constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Diff";
+        this.module = "Diff";
+        this.description = "Compares two inputs (separated by the specified delimiter) and highlights the differences between them.";
+        this.inputType = "string";
+        this.outputType = "html";
+        this.args = [
+            {
+                "name": "Sample delimiter",
+                "type": "binaryString",
+                "value": "\\n\\n"
+            },
+            {
+                "name": "Diff by",
+                "type": "option",
+                "value": ["Character", "Word", "Line", "Sentence", "CSS", "JSON"]
+            },
+            {
+                "name": "Show added",
+                "type": "boolean",
+                "value": true
+            },
+            {
+                "name": "Show removed",
+                "type": "boolean",
+                "value": true
+            },
+            {
+                "name": "Ignore whitespace (relevant for word and line)",
+                "type": "boolean",
+                "value": false
+            }
+        ];
+    }
+
+    /**
+     * @param {string} input
+     * @param {Object[]} args
+     * @returns {html}
+     */
+    run(input, args) {
+        const [
+                sampleDelim,
+                diffBy,
+                showAdded,
+                showRemoved,
+                ignoreWhitespace
+            ] = args,
+            samples = input.split(sampleDelim);
+        let output = "",
+            diff;
+
+        if (!samples || samples.length !== 2) {
+            throw new OperationError("Incorrect number of samples, perhaps you need to modify the sample delimiter or add more samples?");
+        }
+
+        switch (diffBy) {
+            case "Character":
+                diff = JsDiff.diffChars(samples[0], samples[1]);
+                break;
+            case "Word":
+                if (ignoreWhitespace) {
+                    diff = JsDiff.diffWords(samples[0], samples[1]);
+                } else {
+                    diff = JsDiff.diffWordsWithSpace(samples[0], samples[1]);
+                }
+                break;
+            case "Line":
+                if (ignoreWhitespace) {
+                    diff = JsDiff.diffTrimmedLines(samples[0], samples[1]);
+                } else {
+                    diff = JsDiff.diffLines(samples[0], samples[1]);
+                }
+                break;
+            case "Sentence":
+                diff = JsDiff.diffSentences(samples[0], samples[1]);
+                break;
+            case "CSS":
+                diff = JsDiff.diffCss(samples[0], samples[1]);
+                break;
+            case "JSON":
+                diff = JsDiff.diffJson(samples[0], samples[1]);
+                break;
+            default:
+                throw new OperationError("Invalid 'Diff by' option.");
+        }
+
+        for (let i = 0; i < diff.length; i++) {
+            if (diff[i].added) {
+                if (showAdded) output += "<span class='hl5'>" + Utils.escapeHtml(diff[i].value) + "</span>";
+            } else if (diff[i].removed) {
+                if (showRemoved) output += "<span class='hl3'>" + Utils.escapeHtml(diff[i].value) + "</span>";
+            } else {
+                output += Utils.escapeHtml(diff[i].value);
+            }
+        }
+
+        return output;
+    }
+
+}
+
+export default Diff;
diff --git a/src/core/operations/Tar.mjs b/src/core/operations/Tar.mjs
new file mode 100644
index 00000000..a2e8eb70
--- /dev/null
+++ b/src/core/operations/Tar.mjs
@@ -0,0 +1,139 @@
+/**
+ * @author tlwr [toby@toby.codes]
+ * @copyright Crown Copyright 2016
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation";
+import Utils from "../Utils";
+
+/**
+ * Tar operation
+ */
+class Tar extends Operation {
+
+    /**
+     * Tar constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Tar";
+        this.module = "Compression";
+        this.description = "Packs the input into a tarball.<br><br>No support for multiple files at this time.";
+        this.inputType = "byteArray";
+        this.outputType = "File";
+        this.args = [
+            {
+                "name": "Filename",
+                "type": "string",
+                "value": "file.txt"
+            }
+        ];
+    }
+
+    /**
+     * @param {byteArray} input
+     * @param {Object[]} args
+     * @returns {byteArray}
+     */
+    run(input, args) {
+        const Tarball = function() {
+            this.bytes = new Array(512);
+            this.position = 0;
+        };
+
+        Tarball.prototype.addEmptyBlock = function() {
+            const filler = new Array(512);
+            filler.fill(0);
+            this.bytes = this.bytes.concat(filler);
+        };
+
+        Tarball.prototype.writeBytes = function(bytes) {
+            const self = this;
+
+            if (this.position + bytes.length > this.bytes.length) {
+                this.addEmptyBlock();
+            }
+
+            Array.prototype.forEach.call(bytes, function(b, i) {
+                if (typeof b.charCodeAt !== "undefined") {
+                    b = b.charCodeAt();
+                }
+
+                self.bytes[self.position] = b;
+                self.position += 1;
+            });
+        };
+
+        Tarball.prototype.writeEndBlocks = function() {
+            const numEmptyBlocks = 2;
+            for (let i = 0; i < numEmptyBlocks; i++) {
+                this.addEmptyBlock();
+            }
+        };
+
+        const fileSize = input.length.toString(8).padStart(11, "0");
+        const currentUnixTimestamp = Math.floor(Date.now() / 1000);
+        const lastModTime = currentUnixTimestamp.toString(8).padStart(11, "0");
+
+        const file = {
+            fileName: Utils.padBytesRight(args[0], 100),
+            fileMode: Utils.padBytesRight("0000664", 8),
+            ownerUID: Utils.padBytesRight("0", 8),
+            ownerGID: Utils.padBytesRight("0", 8),
+            size: Utils.padBytesRight(fileSize, 12),
+            lastModTime: Utils.padBytesRight(lastModTime, 12),
+            checksum: "        ",
+            type: "0",
+            linkedFileName: Utils.padBytesRight("", 100),
+            USTARFormat: Utils.padBytesRight("ustar", 6),
+            version: "00",
+            ownerUserName: Utils.padBytesRight("", 32),
+            ownerGroupName: Utils.padBytesRight("", 32),
+            deviceMajor: Utils.padBytesRight("", 8),
+            deviceMinor: Utils.padBytesRight("", 8),
+            fileNamePrefix: Utils.padBytesRight("", 155),
+        };
+
+        let checksum = 0;
+        for (const key in file) {
+            const bytes = file[key];
+            Array.prototype.forEach.call(bytes, function(b) {
+                if (typeof b.charCodeAt !== "undefined") {
+                    checksum += b.charCodeAt();
+                } else {
+                    checksum += b;
+                }
+            });
+        }
+        checksum = Utils.padBytesRight(checksum.toString(8).padStart(7, "0"), 8);
+        file.checksum = checksum;
+
+        const tarball = new Tarball();
+        tarball.writeBytes(file.fileName);
+        tarball.writeBytes(file.fileMode);
+        tarball.writeBytes(file.ownerUID);
+        tarball.writeBytes(file.ownerGID);
+        tarball.writeBytes(file.size);
+        tarball.writeBytes(file.lastModTime);
+        tarball.writeBytes(file.checksum);
+        tarball.writeBytes(file.type);
+        tarball.writeBytes(file.linkedFileName);
+        tarball.writeBytes(file.USTARFormat);
+        tarball.writeBytes(file.version);
+        tarball.writeBytes(file.ownerUserName);
+        tarball.writeBytes(file.ownerGroupName);
+        tarball.writeBytes(file.deviceMajor);
+        tarball.writeBytes(file.deviceMinor);
+        tarball.writeBytes(file.fileNamePrefix);
+        tarball.writeBytes(Utils.padBytesRight("", 12));
+        tarball.writeBytes(input);
+        tarball.writeEndBlocks();
+
+        return new File([new Uint8Array(tarball.bytes)], args[0]);
+    }
+
+}
+
+export default Tar;
diff --git a/src/core/operations/Untar.mjs b/src/core/operations/Untar.mjs
new file mode 100644
index 00000000..6bca05d0
--- /dev/null
+++ b/src/core/operations/Untar.mjs
@@ -0,0 +1,138 @@
+/**
+ * @author tlwr [toby@toby.codes]
+ * @copyright Crown Copyright 2016
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation";
+import Utils from "../Utils";
+
+/**
+ * Untar operation
+ */
+class Untar extends Operation {
+
+    /**
+     * Untar constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Untar";
+        this.module = "Compression";
+        this.description = "Unpacks a tarball and displays it per file.";
+        this.inputType = "byteArray";
+        this.outputType = "List<File>";
+        this.presentType = "html";
+        this.args = [];
+        this.patterns = [
+            {
+                "match": "^.{257}\\x75\\x73\\x74\\x61\\x72",
+                "flags": "",
+                "args": []
+            }
+        ];
+    }
+
+    /**
+     * @param {byteArray} input
+     * @param {Object[]} args
+     * @returns {List<File>}
+     */
+    run(input, args) {
+        const Stream = function(input) {
+            this.bytes = input;
+            this.position = 0;
+        };
+
+        Stream.prototype.getBytes = function(bytesToGet) {
+            const newPosition = this.position + bytesToGet;
+            const bytes = this.bytes.slice(this.position, newPosition);
+            this.position = newPosition;
+            return bytes;
+        };
+
+        Stream.prototype.readString = function(numBytes) {
+            let result = "";
+            for (let i = this.position; i < this.position + numBytes; i++) {
+                const currentByte = this.bytes[i];
+                if (currentByte === 0) break;
+                result += String.fromCharCode(currentByte);
+            }
+            this.position += numBytes;
+            return result;
+        };
+
+        Stream.prototype.readInt = function(numBytes, base) {
+            const string = this.readString(numBytes);
+            return parseInt(string, base);
+        };
+
+        Stream.prototype.hasMore = function() {
+            return this.position < this.bytes.length;
+        };
+
+        const stream = new Stream(input),
+            files = [];
+
+        while (stream.hasMore()) {
+            const dataPosition = stream.position + 512;
+
+            const file = {
+                fileName: stream.readString(100),
+                fileMode: stream.readString(8),
+                ownerUID: stream.readString(8),
+                ownerGID: stream.readString(8),
+                size: parseInt(stream.readString(12), 8), // Octal
+                lastModTime: new Date(1000 * stream.readInt(12, 8)), // Octal
+                checksum: stream.readString(8),
+                type: stream.readString(1),
+                linkedFileName: stream.readString(100),
+                USTARFormat: stream.readString(6).indexOf("ustar") >= 0,
+            };
+
+            if (file.USTARFormat) {
+                file.version = stream.readString(2);
+                file.ownerUserName = stream.readString(32);
+                file.ownerGroupName = stream.readString(32);
+                file.deviceMajor = stream.readString(8);
+                file.deviceMinor = stream.readString(8);
+                file.filenamePrefix = stream.readString(155);
+            }
+
+            stream.position = dataPosition;
+
+            if (file.type === "0") {
+                // File
+                let endPosition = stream.position + file.size;
+                if (file.size % 512 !== 0) {
+                    endPosition += 512 - (file.size % 512);
+                }
+
+                file.bytes = stream.getBytes(file.size);
+                files.push(new File([new Uint8Array(file.bytes)], file.fileName));
+                stream.position = endPosition;
+            } else if (file.type === "5") {
+                // Directory
+                files.push(new File([new Uint8Array(file.bytes)], file.fileName));
+            } else {
+                // Symlink or empty bytes
+            }
+        }
+
+        return files;
+    }
+
+    /**
+     * Displays the files in HTML for web apps.
+     *
+     * @param {File[]} files
+     * @returns {html}
+     */
+    async present(files) {
+        return await Utils.displayFilesAsHTML(files);
+    }
+
+}
+
+export default Untar;
diff --git a/src/core/vendor/bzip2.js b/src/core/vendor/bzip2.js
index 03c8c97c..12dc3852 100755
--- a/src/core/vendor/bzip2.js
+++ b/src/core/vendor/bzip2.js
@@ -261,3 +261,5 @@ bzip2.decompress = function(bits, size, len){
   }
   return output;
 }
+
+module.exports = bzip2;
diff --git a/test/index.mjs b/test/index.mjs
index bf5e8115..a20d5fa6 100644
--- a/test/index.mjs
+++ b/test/index.mjs
@@ -35,7 +35,7 @@ import "./tests/operations/CharEnc";
 import "./tests/operations/Ciphers";
 import "./tests/operations/Checksum";
 // import "./tests/operations/Code";
-// import "./tests/operations/Compress";
+import "./tests/operations/Compress";
 // import "./tests/operations/Crypt";
 import "./tests/operations/DateTime";
 import "./tests/operations/Fork";
@@ -43,7 +43,6 @@ import "./tests/operations/Jump";
 import "./tests/operations/ConditionalJump";
 import "./tests/operations/Register";
 import "./tests/operations/Comment";
-
 import "./tests/operations/Hash";
 import "./tests/operations/Hexdump";
 // import "./tests/operations/Image";