diff --git a/layout/reftests/text-svgglyphs/resources/README b/layout/reftests/text-svgglyphs/resources/README
index 92b7995e7e3..14ec605db18 100644
--- a/layout/reftests/text-svgglyphs/resources/README
+++ b/layout/reftests/text-svgglyphs/resources/README
@@ -1,11 +1,37 @@
-Fonts in this directory:
+.woff files for SVG-in-OpenType testing
+=======================================
 
-rubbish.woff contains an SVG table with the contents of rubbish.txt. This is
-not a valid SVG table so no SVG glyphs will be used.
+There are three .woff files in this directory:
+ * nosvg.woff
+ * svg.woff
+ * rubbish.woff
 
-nosvg.woff is derived from the "Liberation" font. It contains no SVG table.
+nosvg.woff
+----------
+This font is Liberation Serif with the addition of a glyph with a UVS selector
+(Liberation fonts do not come with UVS glyphs; one had to be added to test that
+SVG glyphs work with UVS selectors). It contains no 'SVG ' table.
 
-svg.woff is nosvg.woff with an SVG table added. The
-table contains the glyph documents glyphs-base.svg, glyphs-invalid.svg,
-glyphs-objectcolor.svg, glyphs-objectopacity.svg, glyphs-objectstroke.svg,
-glyphs-paintservers.svg and glyphs-transforms.svg.
+svg.woff
+--------
+This font is the same as nosvg.woff above, but with the glyphs-*.svg SVG
+documents from this directory embedded in it using the tools described below.
+
+rubbish.woff
+------------
+This font is the same as nosvg.woff above, but with the addition of an 'SVG '
+table with the contents of rubbish.txt. Its purpose is to test that SVG tables
+without valid XML are ignored.
+
+Creating the Fonts
+------------------
+The tools used here are insertsvg.py from [1] and sfnt2woff from [2].
+
+svg.woff can be recreated with:
+
+woff2sfnt nosvg.woff > nosvg.ttf
+insertsvg.py nosvg.ttf svg.ttf glyphs-*.svg
+sfnt2woff svg.ttf
+
+[1] https://github.com/edf825/SVG-OpenType-Utils
+[2] http://people.mozilla.com/~jkew/woff/