# What is YAML Configuration?

> Human-readable config files that define how software and infrastructure behave.

Canonical: https://www.decimal.app/glossary/yaml-configuration · Last reviewed: 2026-09-23

YAML is a plain-text format widely used for configuration: deployment manifests, CI pipelines, feature settings, and customer-specific overrides. Small edits to these files can change behavior without any code change.

## Why it matters

Config is a frequent hidden cause of customer issues. A wrong indent, a stale value, or a per-customer override can break one account while the code looks fine.

## Best practices

1. Version it like code. Review and history make config changes traceable.
2. Validate on commit. Schema checks catch broken files before deploy.
3. Check config in investigations. When code hasn't changed, look at what config did.

## How Decimal helps

Decimal reads connected config sources alongside code during an investigation, so configuration differences show up as evidence.

## Related terms

- [Feature Flag](https://www.decimal.app/glossary/feature-flag): A switch that turns code paths on or off per customer without a deploy.
- [Regression](https://www.decimal.app/glossary/regression): A bug where something that used to work stops working after a change.
- [Cannot Reproduce](https://www.decimal.app/glossary/cannot-reproduce): The status a ticket gets when engineering can't make the bug happen on their side.

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