.env.default.local

You can generate .env.default.local automatically from .env during project setup:

#!/bin/bash
# scripts/setup-local-defaults.sh
if [ ! -f .env.default.local ]; then
echo "Generating .env.default.local from .env"
grep -v '^#' .env | sed 's/=.*/=safe-local-default/' > .env.default.local
echo "APP_ENV=local" >> .env.default.local
echo "Created .env.default.local – review and copy to .env.local"
fi

Your team uses a feature flag service (LaunchDarkly, Flagsmith). In production, flags are remote. But during local development, you want certain flags to be "on" by default.

Put this in .env.default: FEATURE_NEW_DASHBOARD=false .env.default.local

Put this in your local (gitignored) .env.default.local: FEATURE_NEW_DASHBOARD=true

Now you develop the new dashboard WITHOUT waiting for a remote toggle. When you commit code, you don't accidentally commit the "on" flag, forcing it on for everyone.

Your production server should have NO local files. Set environment variables natively. If a production server sees a .env.default.local file, you’ve likely mounted a volume incorrectly, creating a security risk.

To solve this, we need a hierarchy of configuration. Think of it like CSS stylesheets: defaults, overrides, and local tweaks. The .env.default.local file is the missing link. You can generate

Let's define the layers:

Where the pattern truly shines is with complex data. Many .env readers don't support arrays. But if you build a custom loader, you can merge.

Consider a BLACKLISTED_IPS variable.

.env.default: BLACKLISTED_IPS=127.0.0.1,::1 Your team uses a feature flag service (LaunchDarkly,

.env.default.local: BLACKLISTED_IPS=127.0.0.1,::1,192.168.0.100,10.0.0.5

Your loader should merge these lists, not replace them. This allows local developers to add to lists without destroying defaults.

Most frameworks don't support this out of the box. You need a custom loader. Here is how you implement the hierarchy in different ecosystems.