diff --git a/types/diff_renderer.go b/types/diff_renderer.go
new file mode 100644
index 00000000..441c1979
--- /dev/null
+++ b/types/diff_renderer.go
@@ -0,0 +1,31 @@
+package types
+
+import "tangled.org/core/appview/filetree"
+
+type DiffRenderer interface {
+	// list of file affected by these diffs
+	ChangedFiles() []DiffFileRenderer
+
+	// filetree
+	FileTree() *filetree.FileTreeNode
+
+	Stats() DiffStat
+}
+
+type DiffFileRenderer interface {
+	// html ID for each file in the diff
+	Id() string
+
+	// produce a splitdiff
+	Split() SplitDiff
+
+	// stats for this single file
+	Stats() DiffFileStat
+
+	// old and new name of file
+	Names() DiffFileName
+
+	// whether this diff can be displayed,
+	// returns a reason if not, and the empty string if it can
+	CanRender() string
+}