Env Variable Interpolation Tester

Many .env loaders expand ${VAR} references inside values. The Env Variable Interpolation Tester previews that expansion: every reference is resolved against the file itself, chained variables are expanded, and any undefined or circular reference is flagged.

Paste a file, click Resolve, and read the fully expanded result with a note listing anything that could not be resolved. Catching a typo here is far cheaper than debugging a config that silently fell back to an empty string in production.

• Full resolution: every ${VAR} expanded.
• Chained expansion: A -> B -> C flattened.
• Undefined detection: unresolved names listed.
• Circular detection: A <-> B cycles flagged.
• Order-independent: references any position.
• Copy or download: the resolved file.
• Private: fully client-side.

1. Paste your .env or load the sample.
2. Click Resolve. References expand in place.
3. Read the note for undefined or circular names.
4. Copy the resolved file or fix the problems.

Example 1 — Shared base URL. API_BASE=${API_HOST}/v1 resolves before use, so changing the host updates every consumer.

Example 2 — Chained config. WEBHOOK_URL=${API_BASE}/hooks expands through two levels automatically.

Example 3 — Typo hunt. A misspelled reference stays visible in the output while the note lists the missing key.

Example 4 — Cycle check. Two keys that reference each other are flagged instead of hanging the loader.

Example 5 — Docs preview. The expanded file doubles as a reference of final values for teammates.

• Deterministic: same result as dotenv expansion.
• Safe: undefined refs never silently vanish.
• Cycle-proof: loops detected, not hung.
• Chained: multi-level references work.
• Private: nothing uploaded.