# Small Footprint

A few changes can be made to reduce the footprint of Rhino for embeddings where space is at a premium. On a recent build, the length of js.jar was 603,127 bytes corresponding to 1,171,708 bytes of all uncompressed Rhino classes with debug information included. With various changes js.jar size can be reduced to 204,689 bytes corresponding to 424,774 bytes of uncompressed classes.

### Tools

Most embeddings won't need any of the classes in `org.mozilla.javascript.tools` or any of its sub-packages.

### Optimizer

It is possible to run Rhino with interpreter mode only, allowing you to remove code for classfile generation that include all the classes from `org.mozilla.javascript.optimizer` package.

### JavaAdapter

Implementing the JavaAdapter functionality requires the ability to generate classes on the fly. Removing `org.mozilla.javascript.JavaAdapter` will disable this functionality, but Rhino will otherwise run correctly.

### Class generation library

If you do not include Optimizer or JavaAdapter, then you do not need Rhino library for class file generation and you can remove all the classes from in `org.mozilla.classfile` package.

### Regular Expressions

The package `org.mozilla.javascript.regexp` can be removed. Rhino will continue to run, although it will not be able to execute any regular expression matches. This change saves 47,984 bytes of class files.

### Debug information

Debug information in Rhino classes consumes about 25% of code size and if you can live without that, you can recompile Rhino to remove it.

## smalljs.jar

Ant build script in Rhino supports smalljar target that will generate smalljs.jar that does not include Tools, Optimizer, JavaAdapter and Class generation library, Regular Expressions, E4X implementataion and deprecated files. To build such minimalist jar without debug information, run the following command from the top directory of Rhino distribution:

    ant clean
    ant -Ddebug=off -Dno-regexp=true -Dno-e4x=true smalljar

If you omit `-Dno-regexp=true`, then the resulting smalljs.jar will include Regular Expression support. Similarly omitting `-Dno-e4x=true` results in smalljs.jar that includes runtime support for E4X.

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