Exporting for the Web

HTML5 export allows publishing games made in Godot Engine to the browser. This requires support for the recent technologies WebAssembly and WebGL 2.0 in the user’s browser. Firefox and Chromium (Chrome, Opera) are the most popular supported browsers, Safari and Edge do not work yet. On iOS, all browsers must be based on WebKit (i.e. Safari), so they will also not work.


For security and privacy reasons, many features that work effortlessly on native platforms are more complicated on the web platform. Following is a list of limitations you should be aware of when porting a Godot game to the web.

Exported .html file must not be reused

On export, several text placeholders are replaced in the generated HTML file specifically for the given export options. It must not be reused in further exports.

Using cookies for data persistence

Users must allow cookies (specifically IndexedDB) if persistence of the user:// file system is desired. When playing a game presented in an iframe, third-party cookies must also be enabled. Incognito/private browsing mode also prevents persistence.

The method OS.is_userfs_persistent() can be used to check if the user:// file system is persistent, but can give false positives in some cases.

Full screen and mouse capture

Browsers do not allow arbitrarily entering full screen at any time. The same goes for capturing the cursor. Instead, these actions have to occur as a response to a JavaScript input event. In Godot, this is most easily done by entering full screen from within an input callback such as _input or _unhandled_input.

For the same reason, the full screen project setting is ignored.


The HTTPClient implementation for the HTML5 platform has several restrictions:

  • Accessing or changing the StreamPeer is not possible
  • Blocking mode is not available
  • Cannot progress more than once per frame, so polling in a loop will freeze
  • No chunked responses
  • Host verification cannot be disabled
  • Subject to same-origin policy

Unimplemented functionality

The following functionality is currently unavailable on the HTML5 platform:

  • Threads
  • GDNative
  • Clipboard synchronisation between engine and operating system
  • Networking other than HTTPClient

Check the list of open HTML5 issues on Github to see if functionality you’re interested in has an issue yet. If not, open one to communicate your interest.

Starting exported games from the local file system

Many browsers, Chromium-based browsers specifically, will not load exported projects when opened locally per file:// protocol. To get around this, use a local server.

Python offers an easy method for this, using python -m SimpleHTTPServer with Python 2 or python -m http.server with Python 3 will serve the current working directory on http://localhost:8000.

Serving the files

Exporting for the web generates several files to be served from a web server, including a default HTML page for presentation. A custom HTML file can be used, see Customizing the Web export HTML page.

The generated .html file can be used as DirectoryIndex in Apache servers and can be renamed to e.g. index.html at any time, its name is never depended on by default.

The HTML page is designed to fit the game perfectly without cutting off parts of the canvas when the browser window is scaled to the game’s dimensions. This way it can be inserted into an <iframe> with the game’s size, as is common on most web game hosting sites.

The other exported files are served as they are, next to the .html file, names unchanged. The .wasm file is a binary WebAssembly module implementing the engine. The .pck file is the Godot main pack containing your game. The .js file contains start-up code and is used by the .html file to access the engine. The .png file contains the boot splash image. It is not used in the default HTML page, but is included for custom HTML pages.

The .pck file is binary, usually delivered with the MIME-type application/octet-stream. The .wasm file is delivered as application/wasm.

Delivering the files with server-side compression is recommended especially for the .pck and .wasm files, which are usually large in size. The WebAssembly module compresses particularly well, down to around a quarter of its original size with gzip compression.

Export options

If a runnable web export template is available, a button appears between the Stop scene and Play edited Scene buttons in the editor to quickly open the game in the default browser for testing.

If a path to a Custom HTML shell file is given, it will be used instead of the default HTML page. See Customizing the Web export HTML page.

Head Include is appended into the <head> element of the generated HTML page. This allows to, for example, load webfonts and third-party JavaScript APIs, include CSS, or run JavaScript code.

Turning on Export with Debug when exporting will, in addition to enabling various debug features of the engine, display a debug output below the canvas when using the default HTML page, displaying JavaScript and engine errors. You can also use the browser-integrated developer console, usually opened with the F12 key, which often shows more information, including WebGL errors.

Calling JavaScript from script

In web builds, the JavaScript singleton is implemented. If offers a single method called eval that works similarly to the JavaScript function of the same name. It takes a string as an argument and executes it as JavaScript code. This allows interacting with the browser in ways not possible with script languages integrated into Godot.

func my_func():
    JavaScript.eval("alert('Calling JavaScript per GDScript!');")

The value of the last JavaScript statement is converted to a GDScript value and returned by eval() under certain circumstances:

  • JavaScript number is returned as GDScript float
  • JavaScript boolean is returned as GDScript bool
  • JavaScript string is returned as GDScript String
  • JavaScript ArrayBuffer, TypedArray and DataView are returned as GDScript PoolByteArray
func my_func2():
    var js_return = JavaScript.eval("var myNumber = 1; myNumber + 2;")
    print(js_return) # prints '3.0'

Any other JavaScript value is returned as null.

HTML5 export templates may be built without support for the singleton. With such templates, and on platforms other than HTML5, calling JavaScript.eval will also return null. The availability of the singleton can be checked with the JavaScript feature tag:

func my_func3():
    if OS.has_feature('JavaScript'):
        JavaScript.eval("console.log('The JavaScript singleton is available')")
        print("The JavaScript singleton is NOT available")

The eval method also accepts a second, optional Boolean argument, which specifies whether to execute the code in the global execution context, defaulting to false to prevent polluting the global namespace:

func my_func4():
    # execute in global execution context,
    # thus adding a new JavaScript global variable `MyGlobal`
    JavaScript.eval("var SomeGlobal = {};", true)