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Reference Guide
This manual provides a detailed list of all the input keywords and options available in Radioss.
Obsolete Keywords
Keywords that are still supported, but no longer maintained (*) are considered obsolete.

Welcome
What's New
View new features for Radioss 2025.
Overview
Radioss^® is a leading explicit finite element solver for crash and impact simulation.
Tutorials
Discover Radioss functionality with interactive tutorials.
User Guide
This manual provides details on the features, functionality, and simulation methods available in Altair Radioss.
Reference Guide
This manual provides a detailed list of all the input keywords and options available in Radioss.
- File Extensions and Formats
  Current Radioss format uses the 12x extension format.
- Single File Input
  This format allows running either Starter or Engine with the same file.
- New Keywords in 2025
  New and modified features in Radioss.
- Starter Input
  This manual provides a list of all the model definition keywords and options available in Radioss.
- Engine Input
  This manual provides a list of all the solution definition keywords and options available in Radioss.
- LS-DYNA Input
  This manual provides a list of LS-DYNA input files available in Radioss.
- Multi-Domain
  This manual contains the description of the keywords for the Radioss Multi-Domain.
- Obsolete Keywords
  Keywords that are still supported, but no longer maintained (*) are considered obsolete.
  - Obsolete Starter Keywords
    Block Format Keyword Keywords that are still supported, but no longer maintained (*) are considered obsolete.
  - Obsolete Engine Keywords
    Engine Keyword Keywords that are still supported, but no longer maintained (*) are considered obsolete.
  - Obsolete Optimization Keywords
    Optimization Keyword Keywords that are still supported, but no longer maintained (*) are considered obsolete.
- Other Files
- Definition
Example Guide
This manual presents examples solved using Radioss with regard to common problem types.
Verification Problems
This manual presents solved verification models.
Frequently Asked Questions
This section provides quick responses to typical and frequently asked questions regarding Radioss.
Theory Manual
This manual provides detailed information about the theory used in the Altair Radioss Solver.
User Subroutines
This manual describes the interface between Altair Radioss and user subroutines.

Obsolete Keywords

Keywords that are still supported, but no longer maintained (*) are considered obsolete.

(*) A keyword can become obsolete for several reasons:

Overtaken by a new and more powerful keyword
No longer used
Dismissed

Note: Obsolete keywords will continue to be supported, but they may no longer be exposed in upcoming versions of the manual. Also, new keyword are recommended, instead of obsolete keyword.