# Migrating to release 3.4

DITA-OT 3.4 includes an official Docker container image, a separate plug-in for PDF indexing, a new option to skip HTML5 cover pages, and initial support for project files that allow you to define multiple deliverables in advance, and publish them all at once.

Note:
This topic provides a summary of changes in DITA-OT 3.4 that may require modifications to custom stylesheets or plug-ins. For more information on changes in this release, see the DITA-OT 3.4 Release Notes.

## New indexing plug-in

DITA-OT 3.4 extracts the PDF indexing code to a separate org.dita.index plug-in, and adds a new `depend.org.dita.pdf2.index` extension point that can be used to add custom index processing targets to PDF output.

The built-in index processing has been disabled and deprecated. If you have overridden index processing via the `transform.topic2fo` target in the past, you can set the new org.dita.index.skip property to yes and re-enable the `transform.topic2fo.index` target with `<feature extension="depend.org.dita.pdf2.index" value="transform.topic2fo.index"/>` in your plug-in configuration.

Table 1. New plug-ins
Plug-in | Source code location
--- | ---
org.dita.index | https://github.com/dita-ot/org.dita.index

## Legacy plug-ins removed

DITA-OT 3.4 no longer includes the following legacy transformation plug-ins in the default distribution:

Table 2. Legacy plug-ins
Plug-in | Source code location
--- | ---
TocJS | https://github.com/dita-ot/com.sophos.tocjs
troff | https://github.com/dita-ot/org.dita.troff

Note:
If necessary, legacy plug-ins may be re-installed from earlier DITA-OT distributions, but they are no longer actively maintained or supported by the core toolkit committers. The source code is available on GitHub for anyone interested in maintaining the plug-ins for use with future toolkit versions.

To re-install the plug-in(s) from the plug-in registry at dita-ot.org/plugins, run the following command(s):

    dita --install=com.sophos.tocjs
    dita --install=org.dita.troff