While its update speed can be slower than its newer counterpart, AndroidXRef remains a critical tool for anyone needing to analyze the architecture of older Android releases.
OpenGrok is a legendary source code search and cross-reference engine. Several independent developers host free, public OpenGrok instances dedicated to AOSP. xref aosp free
Most people overlook that cs.android.com (Code Search) is actually a powerful xref tool if you know the shortcuts. While not self-hosted, it remains a xref solution with no setup cost. While its update speed can be slower than