diff --git a/build/replacement.ts b/build/replacement.ts
index fb723d1..3c6dbf1 100644
--- a/build/replacement.ts
+++ b/build/replacement.ts
@@ -7,6 +7,7 @@ export const replacement = new Map([
       "CallableFunction",
       "NewableFunction",
       "IArguments",
+      "String",
       "JSON",
       "ArrayConstructor",
       "ReadonlyArray",
@@ -46,6 +47,7 @@ export const replacement = new Map([
   ["es2015.promise.d.ts", new Set(["PromiseConstructor"])],
   ["es2015.proxy.d.ts", new Set(["ProxyHandler"])],
   ["es2015.reflect.d.ts", new Set(["Reflect"])],
+  ["es2015.symbol.wellknown.d.ts", new Set(["Array", "RegExp", "String"])],
   ["es2017.object.d.ts", new Set(["ObjectConstructor"])],
   ["es2018.asyncgenerator.d.ts", new Set(["AsyncGenerator"])],
   ["es2018.asynciterable.d.ts", new Set(["AsyncIterator"])],
diff --git a/lib/lib.es2015.symbol.wellknown.d.ts b/lib/lib.es2015.symbol.wellknown.d.ts
new file mode 100644
index 0000000..e24d288
--- /dev/null
+++ b/lib/lib.es2015.symbol.wellknown.d.ts
@@ -0,0 +1,119 @@
+/// <reference no-default-lib="true"/>
+
+interface Array<T> {
+  /**
+   * Returns an object whose properties have the value 'true'
+   * when they will be absent when used in a 'with' statement.
+   */
+  readonly [Symbol.unscopables]: { [key: PropertyKey]: boolean };
+}
+
+interface RegExp {
+  /**
+   * Matches a string with this regular expression, and returns an array containing the results of
+   * that search.
+   * @param string A string to search within.
+   */
+  [Symbol.match](string: string): RegExpMatchArray | null;
+
+  /**
+   * Replaces text in a string, using this regular expression.
+   * @param string A String object or string literal whose contents matching against
+   *               this regular expression will be replaced
+   * @param replaceValue A String object or string literal containing the text to replace for every
+   *                     successful match of this regular expression.
+   */
+  [Symbol.replace](string: string, replaceValue: string): string;
+
+  /**
+   * Replaces text in a string, using this regular expression.
+   * @param string A String object or string literal whose contents matching against
+   *               this regular expression will be replaced
+   * @param replacer A function that returns the replacement text.
+   */
+  [Symbol.replace](
+    string: string,
+    replacer: (
+      substring: string,
+      // TODO: could be improved, but blocked by issue:
+      // https://github.com/microsoft/TypeScript/issues/45972
+      ...rest: (string | number)[]
+    ) => string
+  ): string;
+
+  /**
+   * Finds the position beginning first substring match in a regular expression search
+   * using this regular expression.
+   *
+   * @param string The string to search within.
+   */
+  [Symbol.search](string: string): number;
+
+  /**
+   * Returns an array of substrings that were delimited by strings in the original input that
+   * match against this regular expression.
+   *
+   * If the regular expression contains capturing parentheses, then each time this
+   * regular expression matches, the results (including any undefined results) of the
+   * capturing parentheses are spliced.
+   *
+   * @param string string value to split
+   * @param limit if not undefined, the output array is truncated so that it contains no more
+   * than 'limit' elements.
+   */
+  [Symbol.split](string: string, limit?: number): string[];
+}
+
+interface String {
+  /**
+   * Matches a string or an object that supports being matched against, and returns an array
+   * containing the results of that search, or null if no matches are found.
+   * @param matcher An object that supports being matched against.
+   */
+  match(matcher: {
+    [Symbol.match](string: string): RegExpMatchArray | null;
+  }): RegExpMatchArray | null;
+
+  /**
+   * Replaces first match with string or all matches with RegExp.
+   * @param searchValue A object can search for and replace matches within a string.
+   * @param replaceValue A string containing the text to replace for match.
+   */
+  replace(
+    searchValue: {
+      [Symbol.replace](string: string, replaceValue: string): string;
+    },
+    replaceValue: string
+  ): string;
+
+  /**
+   * Replaces text in a string, using an object that supports replacement within a string.
+   * @param searchValue A object can search for and replace matches within a string.
+   * @param replacer A function that returns the replacement text.
+   */
+  replace(
+    searchValue: {
+      [Symbol.replace](
+        string: string,
+        replacer: (substring: string, ...rest: (string | number)[]) => string
+      ): string;
+    },
+    replacer: (substring: string, ...rest: (string | number)[]) => string
+  ): string;
+
+  /**
+   * Finds the first substring match in a regular expression search.
+   * @param searcher An object which supports searching within a string.
+   */
+  search(searcher: { [Symbol.search](string: string): number }): number;
+
+  /**
+   * Split a string into substrings using the specified separator and return them as an array.
+   * @param splitter An object that can split a string.
+   * @param limit A value used to limit the number of elements returned in the array.
+   */
+  split(
+    splitter: { [Symbol.split](string: string, limit?: number): string[] },
+    limit?: number
+  ): string[];
+}
diff --git a/lib/lib.es2021.string.d.ts b/lib/lib.es2021.string.d.ts
index 781d928..0dc3989 100644
--- a/lib/lib.es2021.string.d.ts
+++ b/lib/lib.es2021.string.d.ts
@@ -3,14 +3,14 @@
 interface String {
   /**
    * Replace all instances of a substring in a string, using a regular expression or search string.
-   * @param searchValue A string to search for.
+   * @param searchValue A string or RegExp search value.
    * @param replaceValue A string containing the text to replace for every successful match of searchValue in this string.
    */
   replaceAll(searchValue: string | RegExp, replaceValue: string): string;
 
   /**
    * Replace all instances of a substring in a string, using a regular expression or search string.
-   * @param searchValue A string to search for.
+   * @param searchValue A string or RegExp search value.
    * @param replacer A function that returns the replacement text.
    */
   replaceAll(
@@ -22,4 +22,31 @@ interface String {
       ...rest: (string | number)[]
     ) => string
   ): string;
+
+  /**
+   * Replace all instances of a substring in a string, using a regular expression or search string.
+   * @param searchValue A object can search for and replace matches within a string.
+   * @param replaceValue A string containing the text to replace for match.
+   */
+  replaceAll(
+    searchValue: {
+      [Symbol.replace](string: string, replaceValue: string): string;
+    },
+    replaceValue: string
+  ): string;
+
+  /**
+   * Replace all instances of a substring in a string, using a regular expression or search string.
+   * @param searchValue A object can search for and replace matches within a string.
+   * @param replacer A function that returns the replacement text.
+   */
+  replaceAll(
+    searchValue: {
+      [Symbol.replace](
+        string: string,
+        replacer: (substring: string, ...rest: (string | number)[]) => string
+      ): string;
+    },
+    replacer: (substring: string, ...rest: (string | number)[]) => string
+  ): string;
 }
diff --git a/lib/lib.es5.d.ts b/lib/lib.es5.d.ts
index de11c38..d4c1b58 100644
--- a/lib/lib.es5.d.ts
+++ b/lib/lib.es5.d.ts
@@ -321,6 +321,138 @@ interface IArguments {
   callee: Function;
 }
 
+interface String {
+  /** Returns a string representation of a string. */
+  toString(): string;
+
+  /**
+   * Returns the character at the specified index.
+   * @param pos The zero-based index of the desired character.
+   */
+  charAt(pos: number): string;
+
+  /**
+   * Returns the Unicode value of the character at the specified location.
+   * @param index The zero-based index of the desired character. If there is no character at the specified index, NaN is returned.
+   */
+  charCodeAt(index: number): number;
+
+  /**
+   * Returns a string that contains the concatenation of two or more strings.
+   * @param strings The strings to append to the end of the string.
+   */
+  concat(...strings: string[]): string;
+
+  /**
+   * Returns the position of the first occurrence of a substring.
+   * @param searchString The substring to search for in the string
+   * @param position The index at which to begin searching the String object. If omitted, search starts at the beginning of the string.
+   */
+  indexOf(searchString: string, position?: number): number;
+
+  /**
+   * Returns the last occurrence of a substring in the string.
+   * @param searchString The substring to search for.
+   * @param position The index at which to begin searching. If omitted, the search begins at the end of the string.
+   */
+  lastIndexOf(searchString: string, position?: number): number;
+
+  /**
+   * Determines whether two strings are equivalent in the current locale.
+   * @param that String to compare to target string
+   */
+  localeCompare(that: string): number;
+
+  /**
+   * Matches a string with a regular expression, and returns an array containing the results of that search.
+   * @param regexp A variable name or string literal containing the regular expression pattern and flags.
+   */
+  match(regexp: string | RegExp): RegExpMatchArray | null;
+
+  /**
+   * Replaces text in a string, using a regular expression or search string.
+   * @param searchValue A string or RegExp search value.
+   * @param replaceValue A string containing the text to replace for every successful match of searchValue in this string.
+   */
+  replace(searchValue: string | RegExp, replaceValue: string): string;
+
+  /**
+   * Replaces text in a string, using a regular expression or search string.
+   * @param searchValue A string or RegExp search value.
+   * @param replacer A function that returns the replacement text.
+   */
+  replace(
+    searchValue: string | RegExp,
+    replacer: (
+      substring: string,
+      // TODO: could be improved, but blocked by issue:
+      // https://github.com/microsoft/TypeScript/issues/45972
+      ...rest: (string | number)[]
+    ) => string
+  ): string;
+
+  /**
+   * Finds the first substring match in a regular expression search.
+   * @param regexp The regular expression pattern and applicable flags.
+   */
+  search(regexp: string | RegExp): number;
+
+  /**
+   * Returns a section of a string.
+   * @param start The index to the beginning of the specified portion of stringObj.
+   * @param end The index to the end of the specified portion of stringObj. The substring includes the characters up to, but not including, the character indicated by end.
+   * If this value is not specified, the substring continues to the end of stringObj.
+   */
+  slice(start?: number, end?: number): string;
+
+  /**
+   * Split a string into substrings using the specified separator and return them as an array.
+   * @param separator A string that identifies character or characters to use in separating the string. If omitted, a single-element array containing the entire string is returned.
+   * @param limit A value used to limit the number of elements returned in the array.
+   */
+  split(separator: string | RegExp, limit?: number): string[];
+
+  /**
+   * Returns the substring at the specified location within a String object.
+   * @param start The zero-based index number indicating the beginning of the substring.
+   * @param end Zero-based index number indicating the end of the substring. The substring includes the characters up to, but not including, the character indicated by end.
+   * If end is omitted, the characters from start through the end of the original string are returned.
+   */
+  substring(start: number, end?: number): string;
+
+  /** Converts all the alphabetic characters in a string to lowercase. */
+  toLowerCase(): string;
+
+  /** Converts all alphabetic characters to lowercase, taking into account the host environment's current locale. */
+  toLocaleLowerCase(locales?: string | string[]): string;
+
+  /** Converts all the alphabetic characters in a string to uppercase. */
+  toUpperCase(): string;
+
+  /** Returns a string where all alphabetic characters have been converted to uppercase, taking into account the host environment's current locale. */
+  toLocaleUpperCase(locales?: string | string[]): string;
+
+  /** Removes the leading and trailing white space and line terminator characters from a string. */
+  trim(): string;
+
+  /** Returns the length of a String object. */
+  readonly length: number;
+
+  // IE extensions
+  /**
+   * Gets a substring beginning at the specified location and having the specified length.
+   * @deprecated A legacy feature for browser compatibility
+   * @param from The starting position of the desired substring. The index of the first character in the string is zero.
+   * @param length The number of characters to include in the returned substring.
+   */
+  substr(from: number, length?: number): string;
+
+  /** Returns the primitive value of the specified object. */
+  valueOf(): string;
+
+  readonly [index: number]: string;
+}
+
 type JSONValue =
   | null
   | string