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Environment Variables

Setting boolean values

To set a boolean True, use one of the following string values: "true", "1" or "yes". Any other value will be interpreted as False.

FLET_APP_CONSOLE​

The path to the application's console log file (console.log) in the temporary storage directory.

Its value is set in production mode.

FLET_APP_STORAGE_DATA​

A directory for the storage of persistent application data that is preserved between app updates. It is already pre-created and its location depends on the platform the app is running on.

FLET_APP_STORAGE_TEMP​

A directory for the storage of temporary application files, i.e. cache. It is already pre-created and its location depends on the platform the app is running on.

FLET_APP_USER_MODEL_ID​

Windows AppUserModelID used by the desktop client process for taskbar grouping and pinning.

For apps packaged with flet pack, this value is set automatically so taskbar pins point to the packaged app executable instead of the cached Flet client executable.

FLET_ASSETS_DIR​

Absolute path to the app's assets directory.

In production apps built with flet build, this environment-variable points to the bundled assets absolute location at runtime. Use it when your code needs a filesystem path to bundled files (for example, JSON configs, databases, or model files).

For local runs, it may be unset depending on how the app is started, so use a fallback:

import os
from pathlib import Path
import flet as ft

default_assets_dir = Path(__file__).parent / "assets"
assets_dir = Path(os.environ.get("FLET_ASSETS_DIR", str(default_assets_dir))).resolve()

def main(page: ft.Page):
	...

ft.run(main, assets_dir="assets")

For control properties like Image.src, continue using paths relative to the ft.run(assets_dir=...), as described in the assets cookbook.

FLET_ANDROID_SIGNING_KEY_ALIAS​

Android signing key alias used by flet build for Android app signing.

It is used only when a keystore is configured.

FLET_ANDROID_SIGNING_KEY_PASSWORD​

Android signing key password used by flet build for Android app signing.

If FLET_ANDROID_SIGNING_KEY_STORE_PASSWORD is set but this variable is not, the keystore password is reused as the key password.

FLET_ANDROID_SIGNING_KEY_STORE​

Path to the Android upload keystore (.jks) used by flet build for Android app signing.

FLET_ANDROID_SIGNING_KEY_STORE_PASSWORD​

Android signing keystore password used by flet build for Android app signing.

If FLET_ANDROID_SIGNING_KEY_PASSWORD is set but this variable is not, the key password is reused as the keystore password.

FLET_CLI_NO_RICH_OUTPUT​

Whether to disable rich output in the console.

Defaults to "false".

FLET_PLATFORM​

The platform on which the application is running. Its value is one of the following: "android", "ios", "linux", "macos", "windows" or "fuchsia".

FLET_CLI_SKIP_FLUTTER_DOCTOR​

Whether to skip running flutter doctor when a build fails.

Defaults to False.

FLET_HIDE_WINDOW_ON_START​

Set to true to start app with the main window hidden.

Defaults to False.

FLET_FORCE_WEB_SERVER​

Set to true to force running app as a web app. Automatically set on headless Linux hosts.

FLET_OAUTH_CALLBACK_HANDLER_ENDPOINT​

Custom path for OAuth handler.

Defaults to "/oauth_callback".

FLET_OAUTH_STATE_TIMEOUT​

Maximum allowed time (in seconds) to complete OAuth web flow.

Defaults to 600.

FLET_MAX_UPLOAD_SIZE​

Maximum allowed size (in bytes) of uploaded files.

Default is unlimited.

FLET_SECRET_KEY​

A secret key to sign temporary upload URLs.

FLET_SERVER_IP​

IP address to listen web app on, e.g. "127.0.0.1".

Defaults to 0.0.0.0 - bound to all server IPs.

FLET_SERVER_PORT​

TCP port to run app on.

8000 if the program is running on a Linux server or FLET_FORCE_WEB_SERVER is set; otherwise random port.

FLET_SERVER_UDS_PATH​

The Unix Domain Socket (UDS) path for the Flet server. It enables inter-process communication on Unix-based systems, with its value being a socket file path in the format flet_<pid>.sock.

FLET_SESSION_TIMEOUT​

Session lifetime in seconds.

Defaults to 3600.

FLET_UPLOAD_DIR​

Absolute path to app "upload" directory.

FLET_UPLOAD_HANDLER_ENDPOINT​

Custom path for upload handler.

Defaults to "/upload".

FLET_WEB_APP_PATH​

A URL path after domain name to host web app under, e.g. "/apps/myapp".

Defaults to "/" - host app in the root.

FLET_WEB_NO_CDN​

Set to true to avoid loading CanvasKit, Pyodide, and fonts from CDNs.

FLET_WEBSOCKET_HANDLER_ENDPOINT​

Custom path for WebSocket handler.

Defaults to "/ws".

FLET_WEB_RENDERER​

Web rendering mode: "canvaskit" (default), "skwasm" or "auto".

FLET_WEB_USE_COLOR_EMOJI​

Set to True, true or 1 to load web font with colorful emojis.

FLET_WEB_ROUTE_URL_STRATEGY​

The URL strategy of the web application. Its value can be either "path" (default) or "hash".