Environment Variables
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 cache storage directory
(FLET_APP_STORAGE_CACHE).
Its value is set in production mode.
In a running Flet app, the equivalent of this environment variable is
StoragePaths.get_console_log_filename().
FLET_APP_STORAGE_DATA
A directory for durable application data — databases, state, config — that is preserved between
app updates, backed up by the OS, and never auto-deleted. It is pre-created, app-private, and its
location depends on the platform (it maps to the platform's application support directory:
%APPDATA%\<company>\<product>\data on Windows, ~/Library/Application Support/<bundle-id>/data on
macOS, ~/.local/share/<app-id>/data on Linux, the app-sandboxed support dir on iOS/Android).
In production this directory is also the Python program's current working directory, so relative
file writes (e.g. open("app.db", "w"), sqlite3.connect("app.db")) land here. In flet run (dev
mode) it is <project>/.flet/storage/data.
In a running Flet app, this maps to a data subdirectory of
StoragePaths.get_application_support_directory().
FLET_APP_STORAGE_CACHE
A directory for regenerable cached data. The OS may purge it under storage pressure (and the
platform "clear cache" action wipes it), so only store things you can rebuild. Pre-created and
app-private; it maps to the platform's caches directory (%LOCALAPPDATA%\<company>\<product> on
Windows, ~/Library/Caches/<bundle-id> on macOS, ~/.cache/<app-id> on Linux, the app cache dir on
iOS/Android). In flet run it is <project>/.flet/storage/cache.
In a running Flet app, the equivalent of this environment variable is
StoragePaths.get_application_cache_directory().
FLET_APP_STORAGE_TEMP
A directory for throwaway temporary files — the OS temporary directory (getTemporaryDirectory()).
It is the most volatile of the three and may be cleared between launches, so don't rely on its contents
persisting. (On Android it resolves to the same directory as
FLET_APP_STORAGE_CACHE.) In flet run it is <project>/.flet/storage/temp,
and Python's tempfile is pointed here too (via TMPDIR). Equivalent to Python's
tempfile.gettempdir().
In a running Flet app, the equivalent of this environment variable is
StoragePaths.get_temporary_directory().
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".