Docker Compose Environment Variable Resolver

Preview Docker Compose environment variable substitution, inspect .env values, defaults, required variables, and missing placeholders without running Docker.

Docker Compose YAML

Paste compose.yaml content that contains placeholders such as ${APP_PORT}, ${TAG:-latest}, or ${SECRET_KEY?required}.

.env Values

Shell Overrides

Resolver Settings

Output

Missing Variables

Environment Source

Default Values

Options

Trim whitespace around .env valuesStrip matching quotes from .env valuesInclude source line numbers in reportsInclude resolved value previewMask sensitive values in reportsWarn about missing variablesWarn about required placeholdersWarn about sensitive variable namesWarn about unused .env values

This resolver previews Compose-style substitution only. It does not run Docker, validate YAML, start containers, or read files from your machine.

Previewing Docker Compose Variables Before Running Containers

Docker Compose files often use variables from a .env file or shell environment. Placeholders such as ${APP_PORT:-8080} are helpful, but missing values can cause confusing ports, tags, passwords, and service settings.

This resolver previews those substitutions in the browser. It helps you see which values are resolved, which defaults are used, which required variables are missing, and which .env entries are not used.

When This Compose Variable Resolver Helps

Checking Compose files before sharing them with teammates or committing examples to a repository.

Finding missing variables that would make image tags, ports, secrets, database names, or URLs resolve incorrectly.

Building a clean .env template from placeholders found in a Compose file.

Reviewing whether shell overrides should take priority over .env values in a deployment note or runbook.

How to Use the Docker Compose Environment Variable Resolver

Paste your Docker Compose YAML snippet into the main input box.
Paste matching .env values and optional shell override values.
Choose how missing values, defaults, and environment sources should be handled.
Review the resolved preview, variable report, or generated .env template.
Copy the result into your notes, pull request, runbook, or local Compose workflow.

Example Compose Placeholder

ports:
  - "${APP_PORT:-8080}:80"

environment:
  API_URL: "${API_URL}"
  SECRET_KEY: "${SECRET_KEY?SECRET_KEY is required}"

This Tool Does Not Run Docker Compose

This is a text preview tool. It does not execute Docker, read your local files, contact registries, validate every Compose schema rule, or start containers. Use it to inspect variable substitution before running real Compose commands in your own terminal.

Frequently Asked Questions

What does this Docker Compose variable resolver do?

It scans pasted Compose YAML for variable placeholders, compares them with pasted .env values, applies defaults when selected, and shows what would be substituted.

Does this run docker compose config?

No. It only previews text substitution in your browser. It does not run Docker or call your system shell.

Can it find missing environment variables?

Yes. It reports placeholders that do not have matching .env or shell values and do not have usable defaults.

Can it create a .env template?

Yes. Choose .env template output to generate a starter list of variables found in the Compose file.

Is anything uploaded while resolving variables?

No. Compose text and environment values stay in your browser.