Environment variables

Application environment parameters and operational overrides:

Variable	Default	Component	Description
BRANDKIT_SECRET_KEY	(ephemeral)	app.py	Flask session and CSRF signature key
FLASK_SECRET_KEY	(ephemeral)	app.py	Fallback alias for session key
BRANDKIT_MAX_UPLOAD_MB	16	app.py	Upload size ceiling in megabytes (MAX_CONTENT_LENGTH)
BRANDKIT_CLEANUP_ENABLED	true	app.py	Set to false to disable automated asset sweeps
BRANDKIT_CLEANUP_INTERVAL_HOURS	1	app.py	Frequency of disk cleanup passes
BRANDKIT_RETENTION_HOURS	24	app.py	Retention duration before asset purging
FLASK_ENV	(unset)	app.py	Set to development to enable Werkzeug debugger in dev mode
PORT	8000	app.py, entrypoint.sh	Network binding port
FLASK_APP	(unset)	entrypoint.sh	Fallback flag when Gunicorn is absent

BRANDKIT_SECRET_KEY

# Generate a cryptographically secure key
python3 -c "import secrets; print(secrets.token_hex(32))"

BRANDKIT_SECRET_KEY=<value> docker compose up -d

FLASK_SECRET_KEY is supported as an alternate fallback.

If omitted, BrandKit generates an ephemeral key via os.urandom(24) and logs a warning:

No BRANDKIT_SECRET_KEY set - generating an ephemeral one. Sessions and CSRF
tokens will be invalidated on restart and will not work across multiple
worker processes. Set BRANDKIT_SECRET_KEY in production.

In multi-worker Gunicorn deployments, omitting this variable causes CSRF validation to fail across distinct worker instances.

Store securely

Specify secret keys via environment files (.env) or secrets managers. Do not commit credentials to repository tracking.

BRANDKIT_MAX_UPLOAD_MB

BRANDKIT_MAX_UPLOAD_MB=32 docker compose up -d

Sets the request payload limit. Submissions exceeding this threshold return HTTP 413.

Ensure reverse proxy limits (client_max_body_size in Nginx, request_body max_size in Caddy) equal or exceed this threshold.

The cleanup variables

A background worker thread sweeps static/uploads/ and static/uploads/cache/, deleting files exceeding retention while protecting README.md. It initializes at module import time, running under both Gunicorn and development servers.

# Sweep every 15 minutes, retain files for 1 hour
BRANDKIT_CLEANUP_INTERVAL_HOURS=0.25
BRANDKIT_RETENTION_HOURS=1

Supports fractional hour inputs. Invalid entries fall back to standard defaults with a warning.

# Delegate cleanup to host system cron
BRANDKIT_CLEANUP_ENABLED=false

Disable internal sweeps when multi-worker setups manage cleanup via system cron tasks.

Retention and asset privacy

Files in upload directories are retrievable by name until purged. On shared hosts, consider setting shorter retention intervals:

BRANDKIT_RETENTION_HOURS=1

See Privacy.

FLASK_ENV

FLASK_ENV=development python app.py

Enables the interactive debugger under Werkzeug. This variable does not affect Gunicorn WSGI workers.

Security notice

Never enable FLASK_ENV=development on network-accessible hosts. The interactive debugger permits arbitrary code execution from the browser interface.

PORT

PORT=9000 ./entrypoint.sh
PORT=9000 python app.py

Respected by entrypoint.sh and app.py directly. When running Docker containers, map the host port via "9000:8000".

Sample .env configuration

# .env file for docker compose
BRANDKIT_SECRET_KEY=3f9c1e...replace-with-secure-hex
BRANDKIT_MAX_UPLOAD_MB=32
BRANDKIT_RETENTION_HOURS=2

# docker-compose.yml
services:
  brandkit:
    env_file: .env
    ports:
      - "127.0.0.1:8000:8000"