---
title: segmented_caching.block_size
summary: null
url: >-
  https://www.fastly.com/documentation/reference/vcl/variables/segmented-caching/segmented-caching-block-size
---

**Type:** INTEGER  
**Access:** can be read and set, but not unset

**Available in:** recv, log

The number of bytes constituting each block-aligned file segment.

This variable reports the size of the cacheable unit used for this request.
It will evaluate to `-1` in cases when it is not applicable,
such as when segmented caching is not enabled for the request.