.env · workflow

ENV Merger

Merge .env.base with .env.local and environment overrides. Configurable precedence and conflict resolution.

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later files override earlier ones

merged result

NODE_ENV=development
PORT=3000
DATABASE_URL=postgres://localhost/local
DEBUG=true

source of each key

NODE_ENV.env.base
PORT.env.base
DATABASE_URL.env.local
DEBUG.env.local

What it does

▸Merges any number of .env files in order
▸Later files override earlier ones (standard dotenv behavior)
▸Shows which keys came from which file
▸Copy or download the merged output
▸100% client-side

Privacy

Runs 100% in your browser. Your .env never touches our servers.

client-side only

Usage examples

Case 1 · Base + local override

// .env.base
DATABASE_URL=postgres://localhost/dev
PORT=3000

// .env.local
DATABASE_URL=postgres://localhost/mine

DATABASE_URL=postgres://localhost/mine   (from .env.local)
PORT=3000                                 (from .env.base)

Case 2 · Three-layer merge

// .env          → FEATURE_X=false
// .env.staging  → FEATURE_X=true
// .env.local    → FEATURE_X=debug

FEATURE_X=debug   (from .env.local — the last layer wins)

Case 3 · Non-conflicting merge

// .env.base  → NODE_ENV=production
// .env.prod  → CACHE_URL=redis://...

NODE_ENV=production   (from .env.base)
CACHE_URL=redis://... (from .env.prod)

When to use this tool

→Previewing what your app will actually see after .env.base + .env.local merge
→Onboarding — merging company .env.team with your personal .env.local
→Testing how a new .env.production would layer over staging
→Debugging which of 3+ env files is setting a surprising value

Common mistakes

⚠Assuming the first file wins — dotenv precedence is last-file-wins by default
⚠Forgetting that shell env beats every .env file in most runtimes
⚠Merging test + prod files by accident — keep environments strictly separate
⚠Committing the merged output (if it has secrets) — use it for preview only

ENV Merger — combine multiple .env files

Most dotenv libraries load files in order — .env.base, then .env.local, then .env.development — with each layer overriding the previous. This tool mirrors that behavior in the browser so you can preview the final merged config before shipping.