diff --git a/README.md b/README.md
index bef85ad..c3e2855 100644
--- a/README.md
+++ b/README.md
@@ -25,6 +25,19 @@ Katakana mode does not perform Kanji conversion. Emoji and Hanja searches
 return to the previous mode after use. Hanja lookup currently supports one
 modern Hangul syllable at a time.
 
+## Preedit and candidates
+
+| Frontend | Preedit | Candidates |
+| --- | --- | --- |
+| GTK 3 and IBus | inline in the client | strans popup |
+| XIM PreeditCallbacks | inline through XIM callbacks | strans popup |
+| XIM PreeditPosition | strans popup | strans popup |
+| XIM PreeditNothing | strans popup | strans popup |
+
+XIM supports `UTF8_STRING` and `COMPOUND_TEXT`. Position clients place the
+popup from `XNSpotLocation`; otherwise XIM placement falls back to the bottom
+of the focus or client window.
+
 ## Build and test
 
 Docker is the supported build environment: