diff --git a/site/docs/output_directories.md b/site/docs/output_directories.md
index b007bf3..068a9b7 100644
--- a/site/docs/output_directories.md
+++ b/site/docs/output_directories.md
@@ -26,9 +26,12 @@
 
 * Bazel must be invoked from a directory containing a WORKSPACE file. It reports
   an error if it is not. We call this the _workspace directory_.
-* The _outputRoot_ directory is ~/.cache/bazel. (Unless `$TEST_TMPDIR` is
-  set, as in a test of bazel itself, in which case this directory is used
-  instead.)
+* The _outputRoot_ directory defaults to `~/.cache/bazel` on Linux,
+  `/private/var/tmp` on macOS, and on Windows it defaults to `%HOME%` if set,
+  else `%USERPROFILE%` if set, else the result of calling
+  `SHGetKnownFolderPath()` with the `FOLDERID_Profile` flag set. If the
+  environment variable `$TEST_TMPDIR` is set, as in a test of bazel itself,
+  then that value overrides the default.
 * We stick the Bazel user's build state beneath `outputRoot/_bazel_$USER`. This
   is called the _outputUserRoot_ directory.
 * Beneath the `outputUserRoot` directory, we create an `installBase` directory