> ## Documentation Index
> Fetch the complete documentation index at: https://docs.abbyy.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Backward Compatibility Issues

> Overview of ABBYY FineReader Engine backward compatibility with versions 9.0/9.5, 10, 11, 12, and AI — what changed and what migration may require.

This section contains the description of compatibility issues with the previous versions of ABBYY FineReader Engine:

* [ABBYY FineReader Engine AI and 12 Compatibility](/fine-reader/engine/specifications/backward-compatibility-issues/version-12)
* [ABBYY FineReader Engine 12 and 11 Compatibility](/fine-reader/engine/specifications/backward-compatibility-issues/version-11)
* [ABBYY FineReader Engine 12 and 10 Compatibility](/fine-reader/engine/specifications/backward-compatibility-issues/version-10)
* [ABBYY FineReader Engine 12 and 9 Compatibility](/fine-reader/engine/specifications/backward-compatibility-issues/version-9) (Windows)

## See also

[Specifications](/fine-reader/engine/specifications)

[What's New in ABBYY FineReader Engine 12](/fine-reader/engine/specifications/whats-new)