During the build process, Unity pre-processes template files and evaluates all macros and conditional directives included in those files. As part of this process, Unity finds and replaces all macro declarations with the values the Unity Editor supplies. Unity automatically pre-processes all .html, .php, .css, .js and .json files in the template folder.

The following internal preprocessor variables refer to data in the Project, and Unity assigns value to them at build time according to the values the Editor supplies. JavaScript macros and conditional directives can use these internal preprocessor variables.

Gzip

Brotli

asm.js

JavaScript macros are blocks of JavaScript code in template files, surrounded by three sets of curly brackets. This JavaScript code can use the internal preprocessor variables listed above. These variables are assigned at build time according to the values the Editor supplies. During the build, the preprocessor evaluates all macros and replaces them with the output of the variable.

You can use JavaScript macros to preprocess values supplied by the Editor. These macros can be as complex as you like. They can include multiple operators, loops, functions, and any other JavaScript constructs.

The following example line is from the file used in the Default template:

<div id="unity-build-title">{{{ PRODUCT_NAME }}}</div>

If the value of the Product Name in the Player Settings is set to , the internal preprocessor variable has the value . In the output file, the line appears as:

<div id="unity-build-title">My WebGL Game</div>

Below is a more complex example from the same template file:

canvas.style.background = "url('" + buildUrl + "/{{{ BACKGROUND_FILENAME.replace(/'/g, '%27') }}}') center / cover";

If the target build folder is called , and if you select a background image in the Player Settings, the internal preprocessor variable has the value . In the output file, the line changes into:

canvas.style.background = "url('" + buildUrl + "/Let%27s try WebGL.jpg') center / cover";

Conditional directives # if, # else, and # endif control whether Unity includes a specific portion of the preprocessed file in the output file, or discards it for the current build.

Code that starts with an # if directive and ends with an # endif directive is called a conditional group. Conditional groups can also include # else directives. Unity evaluates the expression written after the # if as a JavaScript expression. If this expression has a truthy value that translates to true when evaluated in a Boolean context, then Unity keeps the line group immediately following the # if directive in the output file. If the # if expression is false, and an # else directive is included in the conditional group, Unity keeps the line group immediately following the # else directive in the output. An example of a conditional group is as follows:

#if EXPRESSION  // this block is included in the output if EXPRESSION has a truthy value#else  // this block is included in the output otherwise#endif

Evaluated JavaScript expressions can include brackets, logical operators and other JavaScript constructs. Conditional directives can be nested.