diff --git a/docs/protocol-extensions.rst b/docs/protocol-extensions.rst
index 52ca6cf8e..68c3d34fd 100644
--- a/docs/protocol-extensions.rst
+++ b/docs/protocol-extensions.rst
@@ -27,6 +27,7 @@ please do so by opening issues in the `GitHub bug tracker
    underlines
    graphics-protocol
    keyboard-protocol
+   text-sizing-protocol
    file-transfer-protocol
    desktop-notifications
    pointer-shapes
diff --git a/docs/text-sizing-protocol.rst b/docs/text-sizing-protocol.rst
new file mode 100644
index 000000000..ba5425aa1
--- /dev/null
+++ b/docs/text-sizing-protocol.rst
@@ -0,0 +1,23 @@
+The text sizing protocol
+==============================================
+
+Classically, because the terminal is a grid of equally spaced characters, only
+a single text size was supported in terminals, with one minor exception, some
+characters were allowed to be rendered in two cells, to accommodate East Asian
+square aspect ratio characters and Emoji. Here by single text size we mean the
+font size of all text on the screen is the same.
+
+This protocol allows text to be displayed in the terminal in different sizes
+both larger and smaller than the base text. It also solves the long standing
+problem of robustly determining the width (in cells) a character should have.
+Applications can interleave text of different sizes on the screen allowing for
+typographic niceties like headlines, superscripts, etc.
+
+Note that this protocol is fully backwards compatible, terminals that implement
+it will continue to work just the same with applications that do not use it.
+Because of this, it is not fully flexible in the font sizes it allows, as it
+still has to work with the grid based character cell fundamental nature of the
+terminal.
+
+Quickstart
+--------------