--- a/toolkit/components/osfile/modules/osfile_async_front.jsm
+++ b/toolkit/components/osfile/modules/osfile_async_front.jsm
@@ -999,31 +999,16 @@ File.move = function move(sourcePath, de
 if (!SharedAll.Constants.Win) {
   File.unixSymLink = function unixSymLink(sourcePath, destPath) {
     return Scheduler.post("unixSymLink", [Type.path.toMsg(sourcePath),
       Type.path.toMsg(destPath)], [sourcePath, destPath]);
   };
 }
 
 /**
- * Gets the number of bytes available on disk to the current user.
- *
- * @param {string} Platform-specific path to a directory on the disk to
- * query for free available bytes.
- *
- * @return {number} The number of bytes available for the current user.
- * @throws {OS.File.Error} In case of any error.
- */
-File.getAvailableFreeSpace = function getAvailableFreeSpace(sourcePath) {
-  return Scheduler.post("getAvailableFreeSpace",
-    [Type.path.toMsg(sourcePath)], sourcePath
-  ).then(Type.uint64_t.fromMsg);
-};
-
-/**
  * Remove an empty directory.
  *
  * @param {string} path The name of the directory to remove.
  * @param {*=} options Additional options.
  *   - {bool} ignoreAbsent If |true|, do not fail if the
  *     directory does not exist yet.
  */
 File.removeEmptyDir = function removeEmptyDir(path, options) {

--- a/toolkit/components/osfile/modules/osfile_async_worker.js
+++ b/toolkit/components/osfile/modules/osfile_async_worker.js
@@ -203,20 +203,16 @@ if (this.Components) {
    copy: function copy(sourcePath, destPath, options) {
      return File.copy(Type.path.fromMsg(sourcePath),
        Type.path.fromMsg(destPath), options);
    },
    move: function move(sourcePath, destPath, options) {
      return File.move(Type.path.fromMsg(sourcePath),
        Type.path.fromMsg(destPath), options);
    },
-   getAvailableFreeSpace: function getAvailableFreeSpace(sourcePath) {
-     return Type.uint64_t.toMsg(
-       File.getAvailableFreeSpace(Type.path.fromMsg(sourcePath)));
-   },
    makeDir: function makeDir(path, options) {
      return File.makeDir(Type.path.fromMsg(path), options);
    },
    removeEmptyDir: function removeEmptyDir(path, options) {
      return File.removeEmptyDir(Type.path.fromMsg(path), options);
    },
    remove: function remove(path, options) {
      return File.remove(Type.path.fromMsg(path), options);

--- a/toolkit/components/osfile/modules/osfile_unix_front.jsm
+++ b/toolkit/components/osfile/modules/osfile_unix_front.jsm
@@ -383,37 +383,16 @@
              ctypes.errno == Const.ENOENT) {
            return;
          }
          throw new File.Error("removeEmptyDir", ctypes.errno, path);
        }
      };
 
      /**
-      * Gets the number of bytes available on disk to the current user.
-      *
-      * @param {string} sourcePath Platform-specific path to a directory on
-      * the disk to query for free available bytes.
-      *
-      * @return {number} The number of bytes available for the current user.
-      * @throws {OS.File.Error} In case of any error.
-      */
-     File.getAvailableFreeSpace = function Unix_getAvailableFreeSpace(sourcePath) {
-       let fileSystemInfo = new Type.statvfs.implementation();
-       let fileSystemInfoPtr = fileSystemInfo.address();
-
-       throw_on_negative("statvfs", (UnixFile.statvfs || UnixFile.statfs)(sourcePath, fileSystemInfoPtr));
-
-       let bytes = new Type.uint64_t.implementation(
-                        fileSystemInfo.f_frsize * fileSystemInfo.f_bavail);
-
-       return bytes.value;
-     };
-
-     /**
       * Default mode for opening directories.
       */
      const DEFAULT_UNIX_MODE_DIR = Const.S_IRWXU;
 
      /**
       * Create a directory.
       *
       * @param {string} path The name of the directory.

--- a/toolkit/components/osfile/modules/osfile_win_front.jsm
+++ b/toolkit/components/osfile/modules/osfile_win_front.jsm
@@ -652,36 +652,16 @@
        }
        // sd will be set only if the function succeeds.
        if (!sd.isNull()) {
            WinFile.LocalFree(Type.HLOCAL.cast(sd));
        }
      };
 
      /**
-      * Gets the number of bytes available on disk to the current user.
-      *
-      * @param {string} sourcePath Platform-specific path to a directory on
-      * the disk to query for free available bytes.
-      *
-      * @return {number} The number of bytes available for the current user.
-      * @throws {OS.File.Error} In case of any error.
-      */
-     File.getAvailableFreeSpace = function Win_getAvailableFreeSpace(sourcePath) {
-       let freeBytesAvailableToUser = new Type.uint64_t.implementation(0);
-       let freeBytesAvailableToUserPtr = freeBytesAvailableToUser.address();
-
-       throw_on_zero("getAvailableFreeSpace",
-         WinFile.GetDiskFreeSpaceEx(sourcePath, freeBytesAvailableToUserPtr, null, null)
-       );
-
-       return freeBytesAvailableToUser.value;
-     };
-
-     /**
       * A global value used to receive data during time conversions.
       */
      let gSystemTime = new Type.SystemTime.implementation();
      let gSystemTimePtr = gSystemTime.address();
 
      /**
       * Utility function: convert a FILETIME to a JavaScript Date.
       */

deleted file mode 100644
--- a/toolkit/components/osfile/tests/xpcshell/test_available_free_space.js
+++ /dev/null
@@ -1,38 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-"use strict";
-
-Components.utils.import("resource://gre/modules/osfile.jsm");
-Components.utils.import("resource://gre/modules/Services.jsm");
-
-do_register_cleanup(function() {
-  Services.prefs.setBoolPref("toolkit.osfile.log", false);
-});
-
-function run_test() {
-  Services.prefs.setBoolPref("toolkit.osfile.log", true);
-
-  run_next_test();
-}
-
-/**
- * Test OS.File.getAvailableFreeSpace
- */
-add_task(async function() {
-  // Set up profile. We will use profile path to query for available free
-  // space.
-  do_get_profile();
-
-  let dir = OS.Constants.Path.profileDir;
-
-  // Sanity checking for the test
-  do_check_true((await OS.File.exists(dir)));
-
-  // Query for available bytes for user
-  let availableBytes = await OS.File.getAvailableFreeSpace(dir);
-
-  do_check_true(!!availableBytes);
-  do_check_true(availableBytes > 0);
-});

--- a/toolkit/components/osfile/tests/xpcshell/xpcshell.ini
+++ b/toolkit/components/osfile/tests/xpcshell/xpcshell.ini
@@ -1,15 +1,14 @@
 [DEFAULT]
 head = head.js
 
 support-files =
   test_loader/module_test_loader.js
 
-[test_available_free_space.js]
 [test_compression.js]
 [test_constants.js]
 [test_creationDate.js]
 [test_duration.js]
 [test_exception.js]
 [test_file_URL_conversion.js]
 [test_loader.js]
 [test_logging.js]