Exporting for the Web¶
HTML5 export allows publishing games made in Godot Engine to the browser. This requires support for WebAssembly and WebGL in the user’s browser.
Important
Use the browser-integrated developer console, usually opened with F12, to view debug information like JavaScript, engine, and WebGL errors.
Attention
Many browsers, including Firefox and Chromium-based browsers,
will not load exported projects when opened locally per
file://
protocol. To get around this, use a local server.
Tip
Python offers an easy method to start a local server.
Use python -m http.server
with Python 3 to serve the
current working directory at http://localhost:8000
.
Attention
There are significant bugs when running HTML5 projects on iOS (regardless of the browser). We recommend using iOS’ native export functionality instead, as it will also result in better performance.
WebGL 2¶
Until the OpenGL ES 3 renderer is removed from Godot in favor of Vulkan, HTML5 export uses WebGL 2 when the GLES3 option is selected.
Warning
Using WebGL 2 is not recommended due to its expected removal from Godot without replacement.
WebGL 2 is not supported in all browsers. Firefox and Chromium (Chrome, Opera) are the most popular supported browsers, Safari and Edge do not work. On iOS, all browsers are based on WebKit (i.e. Safari), so they will also not work.
Godot’s WebGL 2 renderer has issues with 3D and is no longer maintained.
Limitations¶
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.
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. The same goes for
capturing the cursor. Instead, these actions have to occur as a response to
a JavaScript input event. In Godot, this means entering full screen from within
a pressed input event callback such as _input
or _unhandled_input
.
Querying the Input singleton is not sufficient, the relevant
input event must currently be active.
For the same reason, the full screen project setting doesn’t work unless the engine is started from within a valid input event handler. This requires customization of the HTML page.
Audio autoplay¶
Chrome restricts how websites may play audio. It may be necessary for the player to click or tap or press a key to enable audio.
See also
Google offers additional information about their Web Audio autoplay policies.
HTTPClient and HTTPRequest¶
The HTTP classes have several restrictions on the HTML5 platform:
- Accessing or changing the
StreamPeer
is not possible- Threaded/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
Exported .html
file must not be reused¶
Each project must generate their own HTML file. On export, several text placeholders are replaced in the generated HTML file specifically for the given export options. Any direct modifications to the generated HTML file will be lost in future exports. To customize the generated file, see Custom HTML page for Web export.
Boot splash is not displayed¶
The default HTML page does not display the boot splash while loading. However, the image is exported as a PNG file, so custom HTML pages can display it.
Unimplemented functionality¶
The following functionality is currently unavailable on the HTML5 platform:
- Threads
- GDNative
- C#
- Clipboard synchronization between engine and operating system
- Networking other than HTTPClient and WebSocketClient
Tip
Check the list of open HTML5 issues on GitHub to see if the functionality you’re interested in has an issue yet. If not, open one to communicate your interest.
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 Custom HTML page for Web export.
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 draws the game at maximum size within the browser window.
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.
Caution
Delivering the WebAssembly module (.wasm
) with a MIME-type
other than application/wasm can prevent some start-up
optimizations.
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 Custom HTML page for Web export.
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.
Calling JavaScript from script¶
In web builds, the JavaScript
singleton is implemented. It 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
andDataView
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')
""")
else:
print("The JavaScript singleton is NOT available")
Tip
GDScript’s multi-line strings, surrounded by 3 quotes """
as in
my_func3()
above, are useful to keep JavaScript code readable.
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 `SomeGlobal`
JavaScript.eval("var SomeGlobal = {};", true)