How to use this developer tool
- Paste the requested YAML or key/value input.
- Adjust the available options for the target output.
- Select Merge Environments or press Ctrl/Cmd + Enter.
- Review findings, then copy or download the result.
Docker Compose Environment Merger
Merge a Compose service environment block with an override set and see exactly which keys change. Put the Compose YAML before a line containing three dashes, then add KEY=value overrides below it. Choose a service when the file contains more than one. The output is a ready-to-paste environment mapping plus a change summary, processed entirely in your browser.
Developer Input
YAML or line inputAd space
What this developer tool does
Combines the selected service environment with KEY=value overrides. Override keys replace base values, while new keys are appended and unchanged keys remain intact.
The separator is a standalone --- line. The first half is parsed as Compose YAML; the second accepts dotenv-style lines with optional export prefixes and quoted values.
The result is generated locally and should be reviewed before deployment.
Example
The Sample button loads a representative input. Running it produces the same structured output displayed in the result panel, including counts and any findings.
services:
app:
environment:
NODE_ENV: production
LOG_LEVEL: info
---
NODE_ENV=development
API_URL=https://api.example.testUse cases
- Pre-commit configuration review
- Pull request documentation
- Migration inventory preparation
- Training and troubleshooting
Tips for reliable output
- Use spaces instead of tab indentation in YAML.
- Keep multi-document separators on their own line.
- Review generated files before applying them.
- Confirm static findings with official CLI validation.
- Avoid pasting production secrets into shared devices.
Processing details
The separator is a standalone --- line. The first half is parsed as Compose YAML; the second accepts dotenv-style lines with optional export prefixes and quoted values.
Variable expansion, env_file loading, shell command substitution, multiline dotenv values, and YAML anchors are not resolved.
Frequently asked questions
Which value wins when the same environment key exists in both inputs?
The result follows the static rules described on this page. Review finding 1 in context and confirm it with the relevant Docker or Kubernetes command before deployment.
Can the merger read values from a Compose env_file path?
The result follows the static rules described on this page. Review finding 2 in context and confirm it with the relevant Docker or Kubernetes command before deployment.
How do I select a service with its own environment block?
The result follows the static rules described on this page. Review finding 3 in context and confirm it with the relevant Docker or Kubernetes command before deployment.
Are quoted dotenv values preserved when merged into YAML?
Input is processed in your browser. The page does not make a network request with the configuration, but downloaded output and browser history should still be handled according to your security policy.
Does the environment merger send secret values to a server?
The result follows the static rules described on this page. Review finding 5 in context and confirm it with the relevant Docker or Kubernetes command before deployment.