A caching method in which modifications to data in the cache aren't copied to the cache source until absolutely necessary. Write-back caching is available on many microprocessors, including all Intel processors since the 80486. With these microprocessors, data modifications (e.g., write operations) to data stored in the L1 cache aren't copied to main memory until absolutely necessary. In contrast, a write-through cache performs all write operations in parallel -- data is written to main memory and the L1 cache simultaneously.

Write-back caching yields somewhat better performance than write-through caching because it reduces the number of write operations to main memory. With this performance improvement comes a slight risk that data may be lost if the system crashes.

A write-back cache is also called a copy-back cache.