Known limits

The following is a catalogue of known limits in ASDF 1.6.0 .


While there is no hard limit on the size of the Tree, in most practical implementations it will need to be read entirely into main memory in order to interpret it, particularly to support forward references. This imposes a practical limit on its size relative to the system memory on the machine. It is not recommended to store large data sets in the tree directly, instead it should reference blocks.

Literal integer values in the Tree

For practical reasons, integer literals in the Tree must be at most 64-bits within the int64 range. In other words, number must be no greater than 9,223,372,036,854,775,807 or no less than -9,223,372,036,854,775,806.

As of version 1.3.0 of the standard, arbitrary precision integers are supported using integer. Like all tags, use of this type requires library support.


The maximum size of a block header is 65536 bytes.

Since the size of the block is stored in a 64-bit unsigned integer, the largest possible block size is around 18 exabytes. It is likely that other limitations on file size, such as an operating system’s filesystem limitations, will be met long before that.