Difference between Rebuilding and reorganizing indexes in SQL server

 Both rebuild index and reorganize index are used to avoid the index fragmentation. Below are difference between them.

Rebuild index	Reorganize index
Rebuild index if avg_page_space_used_in_percent >=30%	Reorganize index if avg_page_space_used_in_percent >5 and <=30%
Index rebuilding involves dropping and recreating an index entirely. This process rebuilds the index from scratch, organizing the data pages in a contiguous manner.	Index reorganizing is a more lightweight approach that defragments the index by physically reordering the index pages without dropping and recreating the index itself.
When an index is rebuilt, fragmentation is eliminated, and index statistics are updated. This can result in better query performance, especially for heavily fragmented indexes.	Reorganizing reduces fragmentation by compacting the pages and the data within them, but it does not update index statistics.
Index rebuilding requires more system resources and can cause downtime, particularly on large tables or during peak usage hours. It also resets the fill factor, impacting future index maintenance.	Reorganizing is typically faster and less resource-intensive than rebuilding, making it suitable for routine maintenance tasks and scenarios where minimal downtime is essential.
Rebuilding is a drastic measure, but it does its job well. Fragmentation is completely eliminated after it.	Reorganizing may not completely eliminate fragmentation in heavily fragmented indexes, and it does not reset the fill factor.