diff --git a/lib/btc/amount.js b/lib/btc/amount.js
index 1d319e91..e4eada22 100644
--- a/lib/btc/amount.js
+++ b/lib/btc/amount.js
@@ -10,348 +10,353 @@ const assert = require('assert');
 const fixed = require('../utils/fixed');
 
 /**
+ * Amount
  * Represents a bitcoin amount (satoshis internally).
  * @alias module:btc.Amount
- * @constructor
- * @param {(String|Number)?} value
- * @param {String?} unit
  * @property {Amount} value
  */
 
-function Amount(value, unit) {
-  if (!(this instanceof Amount))
-    return new Amount(value, unit);
+class Amount {
+  /**
+   * Create an amount.
+   * @constructor
+   * @param {(String|Number)?} value
+   * @param {String?} unit
+   */
 
-  this.value = 0;
+  constructor(value, unit) {
+    this.value = 0;
 
-  if (value != null)
-    this.fromOptions(value, unit);
-}
+    if (value != null)
+      this.fromOptions(value, unit);
+  }
 
-/**
- * Inject properties from options.
- * @private
- * @param {(String|Number)?} value
- * @param {String?} unit
- * @returns {Amount}
- */
+  /**
+   * Inject properties from options.
+   * @private
+   * @param {(String|Number)?} value
+   * @param {String?} unit
+   * @returns {Amount}
+   */
 
-Amount.prototype.fromOptions = function fromOptions(value, unit) {
-  if (typeof unit === 'string')
-    return this.from(unit, value);
+  fromOptions(value, unit) {
+    if (typeof unit === 'string')
+      return this.from(unit, value);
 
-  if (typeof value === 'number')
-    return this.fromValue(value);
+    if (typeof value === 'number')
+      return this.fromValue(value);
 
-  return this.fromBTC(value);
-};
+    return this.fromBTC(value);
+  }
 
-/**
- * Get satoshi value.
- * @returns {Amount}
- */
+  /**
+   * Get satoshi value.
+   * @returns {Amount}
+   */
 
-Amount.prototype.toValue = function toValue() {
-  return this.value;
-};
-
-/**
- * Get satoshi string or value.
- * @param {Boolean?} num
- * @returns {String|Amount}
- */
-
-Amount.prototype.toSatoshis = function toSatoshis(num) {
-  if (num)
+  toValue() {
     return this.value;
-
-  return this.value.toString(10);
-};
-
-/**
- * Get bits string or value.
- * @param {Boolean?} num
- * @returns {String|Amount}
- */
-
-Amount.prototype.toBits = function toBits(num) {
-  return Amount.encode(this.value, 2, num);
-};
-
-/**
- * Get mbtc string or value.
- * @param {Boolean?} num
- * @returns {String|Amount}
- */
-
-Amount.prototype.toMBTC = function toMBTC(num) {
-  return Amount.encode(this.value, 5, num);
-};
-
-/**
- * Get btc string or value.
- * @param {Boolean?} num
- * @returns {String|Amount}
- */
-
-Amount.prototype.toBTC = function toBTC(num) {
-  return Amount.encode(this.value, 8, num);
-};
-
-/**
- * Get unit string or value.
- * @param {String} unit - Can be `sat`,
- * `ubtc`, `bits`, `mbtc`, or `btc`.
- * @param {Boolean?} num
- * @returns {String|Amount}
- */
-
-Amount.prototype.to = function to(unit, num) {
-  switch (unit) {
-    case 'sat':
-      return this.toSatoshis(num);
-    case 'ubtc':
-    case 'bits':
-      return this.toBits(num);
-    case 'mbtc':
-      return this.toMBTC(num);
-    case 'btc':
-      return this.toBTC(num);
   }
-  throw new Error(`Unknown unit "${unit}".`);
-};
 
-/**
- * Convert amount to bitcoin string.
- * @returns {String}
- */
+  /**
+   * Get satoshi string or value.
+   * @param {Boolean?} num
+   * @returns {String|Amount}
+   */
 
-Amount.prototype.toString = function toString() {
-  return this.toBTC();
-};
+  toSatoshis(num) {
+    if (num)
+      return this.value;
 
-/**
- * Inject properties from value.
- * @private
- * @param {Amount} value
- * @returns {Amount}
- */
-
-Amount.prototype.fromValue = function fromValue(value) {
-  assert(Number.isSafeInteger(value) && value >= 0, 'Value must be an int64.');
-  this.value = value;
-  return this;
-};
-
-/**
- * Inject properties from satoshis.
- * @private
- * @param {Number|String} value
- * @returns {Amount}
- */
-
-Amount.prototype.fromSatoshis = function fromSatoshis(value) {
-  this.value = Amount.decode(value, 0);
-  return this;
-};
-
-/**
- * Inject properties from bits.
- * @private
- * @param {Number|String} value
- * @returns {Amount}
- */
-
-Amount.prototype.fromBits = function fromBits(value) {
-  this.value = Amount.decode(value, 2);
-  return this;
-};
-
-/**
- * Inject properties from mbtc.
- * @private
- * @param {Number|String} value
- * @returns {Amount}
- */
-
-Amount.prototype.fromMBTC = function fromMBTC(value) {
-  this.value = Amount.decode(value, 5);
-  return this;
-};
-
-/**
- * Inject properties from btc.
- * @private
- * @param {Number|String} value
- * @returns {Amount}
- */
-
-Amount.prototype.fromBTC = function fromBTC(value) {
-  this.value = Amount.decode(value, 8);
-  return this;
-};
-
-/**
- * Inject properties from unit.
- * @private
- * @param {String} unit
- * @param {Number|String} value
- * @returns {Amount}
- */
-
-Amount.prototype.from = function from(unit, value) {
-  switch (unit) {
-    case 'sat':
-      return this.fromSatoshis(value);
-    case 'ubtc':
-    case 'bits':
-      return this.fromBits(value);
-    case 'mbtc':
-      return this.fromMBTC(value);
-    case 'btc':
-      return this.fromBTC(value);
+    return this.value.toString(10);
   }
-  throw new Error(`Unknown unit "${unit}".`);
-};
 
-/**
- * Instantiate amount from options.
- * @param {(String|Number)?} value
- * @param {String?} unit
- * @returns {Amount}
- */
+  /**
+   * Get bits string or value.
+   * @param {Boolean?} num
+   * @returns {String|Amount}
+   */
 
-Amount.fromOptions = function fromOptions(value, unit) {
-  return new Amount().fromOptions(value, unit);
-};
+  toBits(num) {
+    return Amount.encode(this.value, 2, num);
+  }
 
-/**
- * Instantiate amount from value.
- * @private
- * @param {Amount} value
- * @returns {Amount}
- */
+  /**
+   * Get mbtc string or value.
+   * @param {Boolean?} num
+   * @returns {String|Amount}
+   */
 
-Amount.fromValue = function fromValue(value) {
-  return new Amount().fromValue(value);
-};
+  toMBTC(num) {
+    return Amount.encode(this.value, 5, num);
+  }
 
-/**
- * Instantiate amount from satoshis.
- * @param {Number|String} value
- * @returns {Amount}
- */
+  /**
+   * Get btc string or value.
+   * @param {Boolean?} num
+   * @returns {String|Amount}
+   */
 
-Amount.fromSatoshis = function fromSatoshis(value) {
-  return new Amount().fromSatoshis(value);
-};
+  toBTC(num) {
+    return Amount.encode(this.value, 8, num);
+  }
 
-/**
- * Instantiate amount from bits.
- * @param {Number|String} value
- * @returns {Amount}
- */
+  /**
+   * Get unit string or value.
+   * @param {String} unit - Can be `sat`,
+   * `ubtc`, `bits`, `mbtc`, or `btc`.
+   * @param {Boolean?} num
+   * @returns {String|Amount}
+   */
 
-Amount.fromBits = function fromBits(value) {
-  return new Amount().fromBits(value);
-};
+  to(unit, num) {
+    switch (unit) {
+      case 'sat':
+        return this.toSatoshis(num);
+      case 'ubtc':
+      case 'bits':
+        return this.toBits(num);
+      case 'mbtc':
+        return this.toMBTC(num);
+      case 'btc':
+        return this.toBTC(num);
+    }
+    throw new Error(`Unknown unit "${unit}".`);
+  }
 
-/**
- * Instantiate amount from mbtc.
- * @param {Number|String} value
- * @returns {Amount}
- */
+  /**
+   * Convert amount to bitcoin string.
+   * @returns {String}
+   */
 
-Amount.fromMBTC = function fromMBTC(value) {
-  return new Amount().fromMBTC(value);
-};
+  toString() {
+    return this.toBTC();
+  }
 
-/**
- * Instantiate amount from btc.
- * @param {Number|String} value
- * @returns {Amount}
- */
+  /**
+   * Inject properties from value.
+   * @private
+   * @param {Amount} value
+   * @returns {Amount}
+   */
 
-Amount.fromBTC = function fromBTC(value) {
-  return new Amount().fromBTC(value);
-};
+  fromValue(value) {
+    assert(Number.isSafeInteger(value) && value >= 0,
+      'Value must be an int64.');
+    this.value = value;
+    return this;
+  }
 
-/**
- * Instantiate amount from unit.
- * @param {String} unit
- * @param {Number|String} value
- * @returns {Amount}
- */
+  /**
+   * Inject properties from satoshis.
+   * @private
+   * @param {Number|String} value
+   * @returns {Amount}
+   */
 
-Amount.from = function from(unit, value) {
-  return new Amount().from(unit, value);
-};
+  fromSatoshis(value) {
+    this.value = Amount.decode(value, 0);
+    return this;
+  }
 
-/**
- * Inspect amount.
- * @returns {String}
- */
+  /**
+   * Inject properties from bits.
+   * @private
+   * @param {Number|String} value
+   * @returns {Amount}
+   */
 
-Amount.prototype.inspect = function inspect() {
-  return `<Amount: ${this.toString()}>`;
-};
+  fromBits(value) {
+    this.value = Amount.decode(value, 2);
+    return this;
+  }
 
-/**
- * Safely convert satoshis to a BTC string.
- * This function explicitly avoids any
- * floating point arithmetic.
- * @param {Amount} value - Satoshis.
- * @returns {String} BTC string.
- */
+  /**
+   * Inject properties from mbtc.
+   * @private
+   * @param {Number|String} value
+   * @returns {Amount}
+   */
 
-Amount.btc = function btc(value, num) {
-  if (typeof value === 'string')
-    return value;
+  fromMBTC(value) {
+    this.value = Amount.decode(value, 5);
+    return this;
+  }
 
-  return Amount.encode(value, 8, num);
-};
+  /**
+   * Inject properties from btc.
+   * @private
+   * @param {Number|String} value
+   * @returns {Amount}
+   */
 
-/**
- * Safely convert a BTC string to satoshis.
- * @param {String} str - BTC
- * @returns {Amount} Satoshis.
- * @throws on parse error
- */
+  fromBTC(value) {
+    this.value = Amount.decode(value, 8);
+    return this;
+  }
 
-Amount.value = function value(str) {
-  if (typeof str === 'number')
-    return str;
+  /**
+   * Inject properties from unit.
+   * @private
+   * @param {String} unit
+   * @param {Number|String} value
+   * @returns {Amount}
+   */
 
-  return Amount.decode(str, 8);
-};
+  from(unit, value) {
+    switch (unit) {
+      case 'sat':
+        return this.fromSatoshis(value);
+      case 'ubtc':
+      case 'bits':
+        return this.fromBits(value);
+      case 'mbtc':
+        return this.fromMBTC(value);
+      case 'btc':
+        return this.fromBTC(value);
+    }
+    throw new Error(`Unknown unit "${unit}".`);
+  }
 
-/**
- * Safely convert satoshis to a BTC string.
- * @param {Amount} value
- * @param {Number} exp - Exponent.
- * @param {Boolean} num - Return a number.
- * @returns {String|Number}
- */
+  /**
+   * Instantiate amount from options.
+   * @param {(String|Number)?} value
+   * @param {String?} unit
+   * @returns {Amount}
+   */
 
-Amount.encode = function encode(value, exp, num) {
-  if (num)
-    return fixed.toFloat(value, exp);
-  return fixed.encode(value, exp);
-};
+  static fromOptions(value, unit) {
+    return new this().fromOptions(value, unit);
+  }
 
-/**
- * Safely convert a BTC string to satoshis.
- * @param {String|Number} value - BTC
- * @param {Number} exp - Exponent.
- * @returns {Amount} Satoshis.
- * @throws on parse error
- */
+  /**
+   * Instantiate amount from value.
+   * @private
+   * @param {Amount} value
+   * @returns {Amount}
+   */
 
-Amount.decode = function decode(value, exp) {
-  if (typeof value === 'number')
-    return fixed.fromFloat(value, exp);
-  return fixed.decode(value, exp);
-};
+  static fromValue(value) {
+    return new this().fromValue(value);
+  }
+
+  /**
+   * Instantiate amount from satoshis.
+   * @param {Number|String} value
+   * @returns {Amount}
+   */
+
+  static fromSatoshis(value) {
+    return new this().fromSatoshis(value);
+  }
+
+  /**
+   * Instantiate amount from bits.
+   * @param {Number|String} value
+   * @returns {Amount}
+   */
+
+  static fromBits(value) {
+    return new this().fromBits(value);
+  }
+
+  /**
+   * Instantiate amount from mbtc.
+   * @param {Number|String} value
+   * @returns {Amount}
+   */
+
+  static fromMBTC(value) {
+    return new this().fromMBTC(value);
+  }
+
+  /**
+   * Instantiate amount from btc.
+   * @param {Number|String} value
+   * @returns {Amount}
+   */
+
+  static fromBTC(value) {
+    return new this().fromBTC(value);
+  }
+
+  /**
+   * Instantiate amount from unit.
+   * @param {String} unit
+   * @param {Number|String} value
+   * @returns {Amount}
+   */
+
+  static from(unit, value) {
+    return new this().from(unit, value);
+  }
+
+  /**
+   * Inspect amount.
+   * @returns {String}
+   */
+
+  inspect() {
+    return `<Amount: ${this.toString()}>`;
+  }
+
+  /**
+   * Safely convert satoshis to a BTC string.
+   * This function explicitly avoids any
+   * floating point arithmetic.
+   * @param {Amount} value - Satoshis.
+   * @returns {String} BTC string.
+   */
+
+  static btc(value, num) {
+    if (typeof value === 'string')
+      return value;
+
+    return Amount.encode(value, 8, num);
+  }
+
+  /**
+   * Safely convert a BTC string to satoshis.
+   * @param {String} str - BTC
+   * @returns {Amount} Satoshis.
+   * @throws on parse error
+   */
+
+  static value(str) {
+    if (typeof str === 'number')
+      return str;
+
+    return Amount.decode(str, 8);
+  }
+
+  /**
+   * Safely convert satoshis to a BTC string.
+   * @param {Amount} value
+   * @param {Number} exp - Exponent.
+   * @param {Boolean} num - Return a number.
+   * @returns {String|Number}
+   */
+
+  static encode(value, exp, num) {
+    if (num)
+      return fixed.toFloat(value, exp);
+    return fixed.encode(value, exp);
+  }
+
+  /**
+   * Safely convert a BTC string to satoshis.
+   * @param {String|Number} value - BTC
+   * @param {Number} exp - Exponent.
+   * @returns {Amount} Satoshis.
+   * @throws on parse error
+   */
+
+  static decode(value, exp) {
+    if (typeof value === 'number')
+      return fixed.fromFloat(value, exp);
+    return fixed.decode(value, exp);
+  }
+}
 
 /*
  * Expose
diff --git a/lib/btc/uri.js b/lib/btc/uri.js
index b4e98d71..34b3d831 100644
--- a/lib/btc/uri.js
+++ b/lib/btc/uri.js
@@ -11,10 +11,9 @@ const Address = require('../primitives/address');
 const Amount = require('./amount');
 
 /**
+ * URI
  * Represents a bitcoin URI.
  * @alias module:btc.URI
- * @constructor
- * @param {Object|String} options
  * @property {Address} address
  * @property {Amount} amount
  * @property {String|null} label
@@ -22,185 +21,194 @@ const Amount = require('./amount');
  * @property {String|null} request
  */
 
-function URI(options) {
-  if (!(this instanceof URI))
-    return new URI(options);
+class URI {
+  /**
+   * Create a bitcoin URI.
+   * @alias module:btc.URI
+   * @constructor
+   * @param {Object|String} options
+   */
 
-  this.address = new Address();
-  this.amount = -1;
-  this.label = null;
-  this.message = null;
-  this.request = null;
+  constructor(options) {
+    this.address = new Address();
+    this.amount = -1;
+    this.label = null;
+    this.message = null;
+    this.request = null;
 
-  if (options)
-    this.fromOptions(options);
-}
-
-/**
- * Inject properties from options object.
- * @private
- * @param {Object|String} options
- * @returns {URI}
- */
-
-URI.prototype.fromOptions = function fromOptions(options) {
-  if (typeof options === 'string')
-    return this.fromString(options);
-
-  if (options.address)
-    this.address.fromOptions(options.address);
-
-  if (options.amount != null) {
-    assert(Number.isSafeInteger(options.amount) && options.amount >= 0,
-      'Amount must be a uint64.');
-    this.amount = options.amount;
+    if (options)
+      this.fromOptions(options);
   }
 
-  if (options.label) {
-    assert(typeof options.label === 'string', 'Label must be a string.');
-    this.label = options.label;
-  }
+  /**
+   * Inject properties from options object.
+   * @private
+   * @param {Object|String} options
+   * @returns {URI}
+   */
 
-  if (options.message) {
-    assert(typeof options.message === 'string', 'Message must be a string.');
-    this.message = options.message;
-  }
+  fromOptions(options) {
+    if (typeof options === 'string')
+      return this.fromString(options);
 
-  if (options.request) {
-    assert(typeof options.request === 'string', 'Request must be a string.');
-    this.request = options.request;
-  }
+    if (options.address)
+      this.address.fromOptions(options.address);
 
-  return this;
-};
+    if (options.amount != null) {
+      assert(Number.isSafeInteger(options.amount) && options.amount >= 0,
+        'Amount must be a uint64.');
+      this.amount = options.amount;
+    }
 
-/**
- * Instantiate URI from options.
- * @param {Object|String} options
- * @returns {URI}
- */
+    if (options.label) {
+      assert(typeof options.label === 'string', 'Label must be a string.');
+      this.label = options.label;
+    }
 
-URI.fromOptions = function fromOptions(options) {
-  return new URI().fromOptions(options);
-};
+    if (options.message) {
+      assert(typeof options.message === 'string', 'Message must be a string.');
+      this.message = options.message;
+    }
 
-/**
- * Parse and inject properties from string.
- * @private
- * @param {String} str
- * @param {Network?} network
- * @returns {URI}
- */
+    if (options.request) {
+      assert(typeof options.request === 'string', 'Request must be a string.');
+      this.request = options.request;
+    }
 
-URI.prototype.fromString = function fromString(str, network) {
-  assert(typeof str === 'string');
-  assert(str.length > 8, 'Not a bitcoin URI.');
-
-  const prefix = str.substring(0, 8);
-
-  assert(prefix === 'bitcoin:', 'Not a bitcoin URI.');
-
-  str = str.substring(8);
-
-  const index = str.indexOf('?');
-
-  let addr, qs;
-  if (index === -1) {
-    addr = str;
-  } else {
-    addr = str.substring(0, index);
-    qs = str.substring(index + 1);
-  }
-
-  this.address.fromString(addr, network);
-
-  if (!qs)
     return this;
-
-  const query = parsePairs(qs);
-
-  if (query.amount) {
-    assert(query.amount.length > 0, 'Value is empty.');
-    assert(query.amount[0] !== '-', 'Value is negative.');
-    this.amount = Amount.value(query.amount);
   }
 
-  if (query.label)
-    this.label = query.label;
+  /**
+   * Instantiate URI from options.
+   * @param {Object|String} options
+   * @returns {URI}
+   */
 
-  if (query.message)
-    this.message = query.message;
+  static fromOptions(options) {
+    return new this().fromOptions(options);
+  }
 
-  if (query.r)
-    this.request = query.r;
+  /**
+   * Parse and inject properties from string.
+   * @private
+   * @param {String} str
+   * @param {Network?} network
+   * @returns {URI}
+   */
 
-  return this;
-};
+  fromString(str, network) {
+    assert(typeof str === 'string');
+    assert(str.length > 8, 'Not a bitcoin URI.');
 
-/**
- * Instantiate uri from string.
- * @param {String} str
- * @param {Network?} network
- * @returns {URI}
- */
+    const prefix = str.substring(0, 8);
 
-URI.fromString = function fromString(str, network) {
-  return new URI().fromString(str, network);
-};
+    assert(prefix === 'bitcoin:', 'Not a bitcoin URI.');
 
-/**
- * Serialize uri to a string.
- * @returns {String}
- */
+    str = str.substring(8);
 
-URI.prototype.toString = function toString() {
-  let str = 'bitcoin:';
+    const index = str.indexOf('?');
 
-  str += this.address.toString();
+    let addr, qs;
+    if (index === -1) {
+      addr = str;
+    } else {
+      addr = str.substring(0, index);
+      qs = str.substring(index + 1);
+    }
 
-  const query = [];
+    this.address.fromString(addr, network);
 
-  if (this.amount !== -1)
-    query.push(`amount=${Amount.btc(this.amount)}`);
+    if (!qs)
+      return this;
 
-  if (this.label)
-    query.push(`label=${escape(this.label)}`);
+    const query = parsePairs(qs);
 
-  if (this.message)
-    query.push(`message=${escape(this.message)}`);
+    if (query.amount) {
+      assert(query.amount.length > 0, 'Value is empty.');
+      assert(query.amount[0] !== '-', 'Value is negative.');
+      this.amount = Amount.value(query.amount);
+    }
 
-  if (this.request)
-    query.push(`r=${escape(this.request)}`);
+    if (query.label)
+      this.label = query.label;
 
-  if (query.length > 0)
-    str += '?' + query.join('&');
+    if (query.message)
+      this.message = query.message;
 
-  return str;
-};
+    if (query.r)
+      this.request = query.r;
 
-/**
- * Inspect bitcoin uri.
- * @returns {String}
- */
+    return this;
+  }
 
-URI.prototype.inspect = function inspect() {
-  return `<URI: ${this.toString()}>`;
-};
+  /**
+   * Instantiate uri from string.
+   * @param {String} str
+   * @param {Network?} network
+   * @returns {URI}
+   */
+
+  static fromString(str, network) {
+    return new this().fromString(str, network);
+  }
+
+  /**
+   * Serialize uri to a string.
+   * @returns {String}
+   */
+
+  toString() {
+    let str = 'bitcoin:';
+
+    str += this.address.toString();
+
+    const query = [];
+
+    if (this.amount !== -1)
+      query.push(`amount=${Amount.btc(this.amount)}`);
+
+    if (this.label)
+      query.push(`label=${escape(this.label)}`);
+
+    if (this.message)
+      query.push(`message=${escape(this.message)}`);
+
+    if (this.request)
+      query.push(`r=${escape(this.request)}`);
+
+    if (query.length > 0)
+      str += '?' + query.join('&');
+
+    return str;
+  }
+
+  /**
+   * Inspect bitcoin uri.
+   * @returns {String}
+   */
+
+  inspect() {
+    return `<URI: ${this.toString()}>`;
+  }
+}
 
 /*
  * Helpers
  */
 
-function BitcoinQuery() {
-  this.amount = null;
-  this.label = null;
-  this.message = null;
-  this.r = null;
+class BitcoinQuery {
+  constructor() {
+    this.amount = null;
+    this.label = null;
+    this.message = null;
+    this.r = null;
+  }
 }
 
 function parsePairs(str) {
   const parts = str.split('&');
   const data = new BitcoinQuery();
+
   let size = 0;
 
   for (const pair of parts) {
@@ -244,7 +252,7 @@ function parsePairs(str) {
         break;
     }
 
-    size++;
+    size += 1;
   }
 
   return data;