* The JSON output formatter now leaves forward slashes unescaped to improve human
readability of URLs and similar strings. Also, a "utf8" option is now provided
to use UTF-8 encoding instead of hex escape codes for most non-ASCII characters.
+* action=opensearch no longer silently ignores the format parameter.
+* action=opensearch now supports format=jsonfm.
=== API internal changes in 1.21 ===
* For debugging only, a new global $wgDebugAPI removes many API restrictions when true.