YML Format Guide

About YML Format

YML is the short file extension for YAML (YAML Ain't Markup Language), a human-readable data serialization format. While .yaml is the official extension, .yml has become the de facto standard in many ecosystems: Docker Compose uses docker-compose.yml, GitHub Actions uses .yml workflow files, Ruby on Rails stores all configuration in .yml files, and Travis CI uses .travis.yml.

There is no technical difference between .yml and .yaml files — both contain the same YAML format data. The shorter .yml extension was popularized by early adopters like Ruby on Rails and has since become common in DevOps tooling. Our converter handles both extensions identically, providing the same high-quality conversion output regardless of which extension your file uses.

Available Conversions

YML/YAML Features

• Human-Readable: Clean syntax with minimal punctuation and indentation-based structure
• Data Types: Strings, integers, floats, booleans, null, dates, and timestamps
• Collections: Sequences (lists) and mappings (dictionaries) with arbitrary nesting
• Multi-Document: Multiple documents in a single file separated by ---
• Anchors & Aliases: Reference and reuse repeated data structures
• Comments: Full comment support with # character
• Unicode: Full UTF-8 encoding support
• JSON Superset: YAML 1.2 is a superset of JSON
• Multi-line Strings: Literal (|) and folded (>) block styles

Where .yml Extension is Used

• Docker Compose: docker-compose.yml — container orchestration
• GitHub Actions: .github/workflows/*.yml — CI/CD pipelines
• Travis CI: .travis.yml — continuous integration
• Ruby on Rails: config/database.yml, config/locales/*.yml
• GitLab CI: .gitlab-ci.yml — CI/CD configuration
• CircleCI: .circleci/config.yml — build configuration
• Ansible: Playbooks and role definitions
• Kubernetes: Pod, Service, Deployment manifests
• Helm Charts: values.yml — package manager templates
• Jekyll: _config.yml — static site configuration