diff --git a/BUILDING.md b/BUILDING.md
index 924f6c9..a684872 100644
--- a/BUILDING.md
+++ b/BUILDING.md
@@ -2,9 +2,18 @@
 
 ## Build Prerequisites
 
-  * [CMake](https://cmake.org/download/) 2.8.11 or later is required.
+The standalone CMake build is primarily intended for developers. If embedding
+BoringSSL into another project with a pre-existing build system, see
+[INCORPORATING.md](/INCORPORATING.md).
 
-  * Perl 5.6.1 or later is required. On Windows,
+Unless otherwise noted, build tools must at most five years old, matching
+[Abseil guidelines](https://abseil.io/about/compatibility). If in doubt, use the
+most recent stable version of each tool.
+
+  * [CMake](https://cmake.org/download/) 2.8.12 or later is required. Note we
+    will begin requiring CMake 3.0 in 2019.
+
+  * A recent version of Perl is required. On Windows,
     [Active State Perl](http://www.activestate.com/activeperl/) has been
     reported to work, as has MSYS Perl.
     [Strawberry Perl](http://strawberryperl.com/) also works but it adds GCC
@@ -13,28 +22,23 @@
     If Perl is not found by CMake, it may be configured explicitly by setting
     `PERL_EXECUTABLE`.
 
-  * On Windows you currently must use [Ninja](https://ninja-build.org/)
-    to build; on other platforms, it is not required, but recommended, because
-    it makes builds faster.
-
-  * If you need to build Ninja from source, then a recent version of
-    [Python](https://www.python.org/downloads/) is required (Python 2.7.5 works).
+  * Building with [Ninja](https://ninja-build.org/) instead of Make is
+    recommended, because it makes builds faster. On Windows, CMake's Visual
+    Studio generator may also work, but it not tested regularly and requires
+    recent versions of CMake for assembly support.
 
   * On Windows only, [NASM](https://www.nasm.us/) is required. If not found
     by CMake, it may be configured explicitly by setting
     `CMAKE_ASM_NASM_COMPILER`.
 
-  * A C compiler is required. On Windows, MSVC 14 (Visual Studio 2015) or later
-    with Platform SDK 8.1 or later are supported. Recent versions of GCC (4.8+)
-    and Clang should work on non-Windows platforms, and maybe on Windows too.
-    To build the tests, you also need a C++ compiler with C++11 support.
+  * C and C++ compilers with C++11 support are required. On Windows, MSVC 14
+    (Visual Studio 2015) or later with Platform SDK 8.1 or later are supported.
+    Recent versions of GCC (4.8+) and Clang should work on non-Windows
+    platforms, and maybe on Windows too.
 
   * The most recent stable version of [Go](https://golang.org/dl/) is required.
-    If not found by CMake, the go executable may be configured explicitly by
-    setting `GO_EXECUTABLE`.
-
-  * To build the x86 and x86\_64 assembly, your assembler must support AVX2
-    instructions and MOVBE. If using GNU binutils, you must have 2.22 or later
+    Note Go is exempt from the five year support window. If not found by CMake,
+    the go executable may be configured explicitly by setting `GO_EXECUTABLE`.
 
 ## Building