Environment Variables

:::tip[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".