diff --git a/src/common/parser/Params.test.ts b/src/common/parser/Params.test.ts
new file mode 100644
index 000000000..564b0d565
--- /dev/null
+++ b/src/common/parser/Params.test.ts
@@ -0,0 +1,182 @@
+/**
+ * Copyright (c) 2019 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+import { assert } from 'chai';
+import { Params } from 'common/parser/Params';
+
+/** `Params` parser shim */
+function parse(params: Params, s: string): void {
+  params.reset();
+  params.addParam(0);
+  let isSub = false;
+  for (let i = 0; i < s.length; ++i) {
+    let code = s.charCodeAt(i);
+    do {
+      switch (code) {
+        case 0x3b:
+          params.addParam(0);
+          isSub = false;
+          break;
+        case 0x3a:
+          params.addSubParam(-1);
+          isSub = true;
+          break;
+        default:  // 0x30 - 0x39
+          if (isSub) params.addSubParamDigit(code - 48);
+          else params.addParamDigit(code - 48);
+      }
+    } while (++i < s.length && (code = s.charCodeAt(i)) > 0x2f && code < 0x3c);
+  }
+}
+
+
+describe('Params', () => {
+  it('should respect ctor args', () => {
+    const params = new Params(12, 23);
+    assert.equal(params.params.length, 12);
+    assert.equal(params.subParams.length, 23);
+    assert.deepEqual(params.toArray(), []);
+  });
+  it('addParam', () => {
+    const params = new Params();
+    params.addParam(1);
+    assert.equal(params.length, 1);
+    assert.deepEqual(Array.prototype.slice.call(params.params, 0, params.length), [1]);
+    assert.deepEqual(params.toArray(), [1]);
+    params.addParam(23);
+    assert.equal(params.length, 2);
+    assert.deepEqual(Array.prototype.slice.call(params.params, 0, params.length), [1, 23]);
+    assert.deepEqual(params.toArray(), [1, 23]);
+    assert.equal(params.subParamsLength, 0);
+  });
+  it('addSubParam', () => {
+    const params = new Params();
+    params.addParam(1);
+    params.addSubParam(2);
+    params.addSubParam(3);
+    assert.equal(params.length, 1);
+    assert.equal(params.subParamsLength, 2);
+    assert.deepEqual(params.toArray(), [1, [2, 3]]);
+    params.addParam(12345);
+    params.addSubParam(-1);
+    assert.equal(params.length, 2);
+    assert.equal(params.subParamsLength, 3);
+    assert.deepEqual(params.toArray(), [1, [2, 3], 12345, [-1]]);
+  });
+  it('should not add sub params without previous param', () => {
+    const params = new Params();
+    params.addSubParam(2);
+    params.addSubParam(3);
+    assert.equal(params.length, 0);
+    assert.equal(params.subParamsLength, 0);
+    assert.deepEqual(params.toArray(), []);
+    params.addParam(1);
+    params.addSubParam(2);
+    params.addSubParam(3);
+    assert.equal(params.length, 1);
+    assert.equal(params.subParamsLength, 2);
+    assert.deepEqual(params.toArray(), [1, [2, 3]]);
+  });
+  it('reset', () => {
+    const params = new Params();
+    params.addParam(1);
+    params.addSubParam(2);
+    params.addSubParam(3);
+    params.addParam(12345);
+    params.addSubParam(-1);
+    params.reset();
+    assert.equal(params.length, 0);
+    assert.equal(params.subParamsLength, 0);
+    assert.deepEqual(params.toArray(), []);
+    params.addParam(1);
+    params.addSubParam(2);
+    params.addSubParam(3);
+    params.addParam(12345);
+    params.addSubParam(-1);
+    assert.equal(params.length, 2);
+    assert.equal(params.subParamsLength, 3);
+    assert.deepEqual(params.toArray(), [1, [2, 3], 12345, [-1]]);
+  });
+  it('Params.fromArray --> toArray', () => {
+    let data: (number | number[])[] = [];
+    assert.deepEqual(Params.fromArray(data).toArray(), data);
+    data = [1, [2, 3], 12345, [-1]];
+    assert.deepEqual(Params.fromArray(data).toArray(), data);
+    data = [38, 2, 50, 100, 150];
+    assert.deepEqual(Params.fromArray(data).toArray(), data);
+    data = [38, 2, 50, 100, [150]];
+    assert.deepEqual(Params.fromArray(data).toArray(), data);
+    data = [38, [2, 50, 100, 150]];
+    assert.deepEqual(Params.fromArray(data).toArray(), data);
+    // strip empty sub params
+    data = [38, [2, 50, 100, 150], 5, [], 6];
+    assert.deepEqual(Params.fromArray(data).toArray(), [38, [2, 50, 100, 150], 5, 6]);
+  });
+  it('hasSubParams / getSubParams', () => {
+    const params = Params.fromArray([38, [2, 50, 100, 150], 5, [], 6]);
+    assert.equal(params.hasSubParams(0), true);
+    assert.deepEqual(params.getSubParams(0), new Int16Array([2, 50, 100, 150]));
+    assert.equal(params.hasSubParams(1), false);
+    assert.deepEqual(params.getSubParams(1), null);
+    assert.equal(params.hasSubParams(2), false);
+    assert.deepEqual(params.getSubParams(2), null);
+  });
+  it('getSubParamsAll', () => {
+    const params = Params.fromArray([1, [2, 3], 7, 12345, [-1]]);
+    assert.deepEqual(params.getSubParamsAll(), {0: new Int16Array([2, 3]), 2: new Int16Array([-1])});
+  });
+  describe('parse tests', () => {
+    it('param defaults to 0 (ZDM - zero default mode)', () => {
+      const params = new Params();
+      parse(params, '');
+      assert.deepEqual(params.toArray(), [0]);
+    });
+    it('sub param defaults to -1', () => {
+      const params = new Params();
+      parse(params, ':');
+      assert.deepEqual(params.toArray(), [0, [-1]]);
+    });
+    it('should correctly reset on new sequence', () => {
+      const params = new Params();
+      parse(params, '1;2;3');
+      assert.deepEqual(params.toArray(), [1, 2, 3]);
+      parse(params, '4');
+      assert.deepEqual(params.toArray(), [4]);
+      parse(params, '4::123:5;6;7');
+      assert.deepEqual(params.toArray(), [4, [-1, 123, 5], 6, 7]);
+      parse(params, '');
+      assert.deepEqual(params.toArray(), [0]);
+    });
+    it('should handle length restrictions correctly', () => {
+      // restrict to 3 params and 3 sub params
+      const params = new Params(3, 3);
+      parse(params, '1;2;3');
+      assert.deepEqual(params.toArray(), [1, 2, 3]);
+      parse(params, '4');
+      assert.deepEqual(params.toArray(), [4]);
+      parse(params, '4::123:5;6;7');
+      assert.deepEqual(params.toArray(), [4, [-1, 123, 5], 6, 7]);
+      parse(params, '');
+      assert.deepEqual(params.toArray(), [0]);
+      // overlong params
+      parse(params, '1;2;3;4;5;6;7');
+      assert.deepEqual(params.toArray(), [1, 2, 3]);
+      // overlong sub params
+      parse(params, '4;38:2::50:100:150;48:5:22');
+      assert.deepEqual(params.toArray(), [4, 38, [2, -1, 50], 48]);
+    });
+    it('typical sequences', () => {
+      const params = new Params();
+      // SGR with semicolon syntax
+      parse(params, '0;4;38;2;50;100;150;48;5;22');
+      assert.deepEqual(params.toArray(), [0, 4, 38, 2, 50, 100, 150, 48, 5, 22]);
+      // SGR mixed style (partly wrong)
+      parse(params, '0;4;38;2;50:100:150;48;5:22');
+      assert.deepEqual(params.toArray(), [0, 4, 38, 2, 50, [100, 150], 48, 5, [22]]);
+      // SGR colon style
+      parse(params, '0;4;38:2::50:100:150;48:5:22');
+      assert.deepEqual(params.toArray(), [0, 4, 38, [2, -1, 50, 100, 150], 48, [5, 22]]);
+    });
+  });
+});
diff --git a/src/common/parser/Params.ts b/src/common/parser/Params.ts
new file mode 100644
index 000000000..f9031b77f
--- /dev/null
+++ b/src/common/parser/Params.ts
@@ -0,0 +1,238 @@
+/**
+ * Copyright (c) 2019 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+import { StringToUtf32 } from 'common/input/TextDecoder';
+
+// TODO: move to Types
+interface IParamsConstructor {
+  new(maxLength: number, maxSubParamsLength: number): IParams;
+  fromArray(values: (number | number[])[]): IParams;
+}
+
+interface IParams {
+  /** from ctor */
+  maxLength: number;
+  maxSubParamsLength: number;
+
+  /** param values and its length */
+  params: Int16Array;
+  length: number;
+
+  /** sub params and its length */
+  subParams: Int16Array;
+  subParamsLength: number;
+
+  /** methods */
+  clone(): IParams;
+  toArray(): (number | number[])[];
+  reset(): void;
+  addParam(value: number): void;
+  addSubParam(value: number): void;
+  hasSubParams(idx: number): boolean;
+  getSubParams(idx: number): Int16Array | null;
+  getSubParamsAll(): {[idx: number]: Int16Array};
+}
+
+/**
+ * Params storage class.
+ * This type is used by the parser to acuumulate sequence parameters and sub parameters
+ * and transmit them to the input handler actions.
+ * Note: The params object for the handler actions is borrowed from the parser
+ * and will be lost after the handler exits. Use either `toArray` or `clone` to get
+ * a stable copy of the data.
+ */
+export class Params implements IParams {
+  // params store and length
+  public params: Int16Array;
+  public length: number;
+
+  // sub params store and length
+  public subParams: Int16Array;
+  public subParamsLength: number;
+
+  // sub params offsets from param: param idx --> [start, end] offset
+  private _subParamsIdx: Uint16Array;
+  private _rejectDigits: boolean;
+  private _rejectSubDigits: boolean;
+
+  /**
+   * Create a `Params` type from JS array representation.
+   */
+  public static fromArray(values: (number | number[])[]): Params {
+    const params = new Params();
+    if (!values.length) {
+      return params;
+    }
+    // skip leading sub params
+    for (let i = (values[0] instanceof Array) ? 1 : 0; i < values.length; ++i) {
+      const value = values[i];
+      if (value instanceof Array) {
+        for (let k = 0; k < value.length; ++k) {
+          params.addSubParam(value[k]);
+        }
+      } else {
+        params.addParam(value);
+      }
+    }
+    return params;
+  }
+
+  /**
+   * @param maxLength max length of storable parameters
+   * @param maxSubParamsLength max length of storable sub parameters
+   */
+  constructor(public maxLength: number = 32, public maxSubParamsLength: number = 32) {
+    // precondition: subparams cannot be more than 256
+    if (maxSubParamsLength > 256) {
+      throw new Error('maxSubParamsLength must not be greater than 256');
+    }
+    this.params = new Int16Array(maxLength);
+    this.length = 0;
+    this.subParams = new Int16Array(maxSubParamsLength);
+    this.subParamsLength = 0;
+    this._subParamsIdx = new Uint16Array(maxLength);
+    this._rejectDigits = false;
+    this._rejectSubDigits = false;
+  }
+
+  /**
+   * Clone object to its own copy.
+   */
+  public clone(): Params {
+    const newParams = new Params(this.maxLength, this.maxSubParamsLength);
+    newParams.params.set(this.params);
+    newParams.length = this.length;
+    newParams.subParams.set(this.subParams);
+    newParams.subParamsLength = this.subParamsLength;
+    newParams._subParamsIdx.set(this._subParamsIdx);
+    return newParams;
+  }
+
+  /**
+   * Get a JS array representation of the current parameters and sub parameters.
+   * The array is structured as follows:
+   *    sequence: "1;2:3:4;5::6"
+   *    array   : [1, 2, [3, 4], 5, [-1, 6]]
+   */
+  public toArray(): (number | number[])[] {
+    const res: (number | number[])[] = [];
+    for (let i = 0; i < this.length; ++i) {
+      res.push(this.params[i]);
+      const start = this._subParamsIdx[i] >> 8;
+      const end = this._subParamsIdx[i] & 0xFF;
+      if (end - start > 0) {
+        res.push(Array.prototype.slice.call(this.subParams, start, end));
+      }
+    }
+    return res;
+  }
+
+  /**
+   * Reset to initial empty state.
+   */
+  public reset(): void {
+    this.length = 0;
+    this.subParamsLength = 0;
+    this._rejectDigits = false;
+    this._rejectSubDigits = false;
+  }
+
+  /**
+   * Add a parameter value.
+   * `Params` only stores up to `maxLength` parameters, any later
+   * parameter will be ignored.
+   * Note: VT devices only stored up to 16 values, xterm seems to
+   * store up to 30.
+   */
+  public addParam(value: number): void {
+    if (this.length >= this.maxLength) {
+      this._rejectDigits = true;
+      return;
+    }
+    this._subParamsIdx[this.length] = this.subParamsLength << 8 | this.subParamsLength;
+    this.params[this.length++] = value;
+  }
+
+  /**
+   * Add a sub parameter value.
+   * The sub parameter is automatically associated with the last parameter value.
+   * If there is no parameter yet the sub parameter is ingored.
+   * `Params` only stores up to `subParamsLength` sub parameters, any later
+   * sub parameter will be ignored.
+   */
+  public addSubParam(value: number): void {
+    if (!this.length || this.subParamsLength >= this.maxSubParamsLength) {
+      this._rejectSubDigits = true;
+      return;
+    }
+    this.subParams[this.subParamsLength++] = value;
+    this._subParamsIdx[this.length - 1]++;
+  }
+
+  /**
+   * Whether parameter at index `idx` has sub parameters.
+   */
+  public hasSubParams(idx: number): boolean {
+    return ((this._subParamsIdx[idx] & 0xFF) - (this._subParamsIdx[idx] >> 8) > 0);
+  }
+
+  /**
+   * Return sub parameters for parameter at index `idx`.
+   * Note: The values are borrowed, thus you need to copy
+   * the values if you need to hold them in nonlocal scope.
+   */
+  public getSubParams(idx: number): Int16Array | null {
+    const start = this._subParamsIdx[idx] >> 8;
+    const end = this._subParamsIdx[idx] & 0xFF;
+    if (end - start > 0) {
+      return this.subParams.subarray(start, end);
+    }
+    return null;
+  }
+
+  /**
+   * Return all kown sub parameters as {idx: subparams} mapping.
+   * Note: The values are not borrowed, thus it is safe to hold
+   * them without copying.
+   */
+  public getSubParamsAll(): {[idx: number]: Int16Array} {
+    const result: {[idx: number]: Int16Array} = {};
+    for (let i = 0; i < this.length; ++i) {
+      const start = this._subParamsIdx[i] >> 8;
+      const end = this._subParamsIdx[i] & 0xFF;
+      if (end - start > 0) {
+        result[i] = this.subParams.slice(start, end);
+      }
+    }
+    return result;
+  }
+
+  /**
+   * Add a single digit value to current parameter.
+   * This is used by the parser to account digits on a char by char basis.
+   * Do not use this method directly, consider using `addParam` instead.
+   */
+  public addParamDigit(value: number): void {
+    if (this._rejectDigits) {
+      return;
+    }
+    this.params[this.length - 1] = this.params[this.length - 1] * 10 + value;
+  }
+
+  /**
+   * Add a single digit value to current sub parameter.
+   * This is used by the parser to account digits on a char by char basis.
+   * Do not use this method directly, consider using `addSubParam` instead.
+   */
+  public addSubParamDigit(value: number): void {
+    if (!this.subParamsLength || this._rejectDigits || this._rejectSubDigits) {
+      return;
+    }
+    if (this.subParams[this.subParamsLength - 1] === -1) {
+      this.subParams[this.subParamsLength - 1] = value;
+    } else {
+      this.subParams[this.subParamsLength - 1] = this.subParams[this.subParamsLength - 1] * 10 + value;
+    }
+  }
+}