c3x

Cloud cost estimation with built-in optimization recommendations, budget guardrails, what-if analysis, and fully offline mode — no API key required.

Get started

# macOS / Linux
brew install c3xdev/tap/c3x

# Docker
docker pull c3xdev/c3x

# Or download from GitHub Releases
# https://github.com/c3xdev/c3x/releases

c3x estimate --path /path/to/terraform

See our quick start guide for more details.

What makes C3X different

Cost optimization recommendations

C3X doesn't just show costs — it suggests how to save money.

c3x recommend --path .
# Or inline with estimate:
c3x estimate --path . --recommend

3 recommendation(s) found:

  1. Upgrade to newer instance generation (m5.xlarge -> m7i.xlarge)
     Resource: aws_instance.web (aws_instance)
     The m7i family has better price-performance than m5.

  2. Switch EBS volume from gp2 to gp3
     Resource: aws_ebs_volume.data (aws_ebs_volume)
     gp3 volumes are up to 20% cheaper with better baseline performance.

  3. Consider VPC endpoints to reduce NAT Gateway costs
     Resource: aws_nat_gateway.main (aws_nat_gateway)
     NAT Gateway charges $0.045/GB. VPC endpoints can eliminate these charges.

Budget guardrails in CI/CD

Enforce cost limits in your pipeline — no paid subscription required.

# Fail the pipeline if monthly cost exceeds $1,000
c3x estimate --path . --budget 1000

# Fail if cost increases more than 20%
c3x diff --path . --compare-to baseline.json --budget-increase 20

What-if cost scenarios

Explore cost impact of changes without modifying Terraform code.

# What if we use a bigger instance?
c3x estimate --path . --what-if 'aws_instance.web.instance_type=m6i.8xlarge'

# What if we enable multi-AZ?
c3x estimate --path . --what-if 'aws_db_instance.main.multi_az=true'

Fully offline mode

Download pricing data once, estimate forever. No network calls, no telemetry, no API key.

# Download pricing data (~50MB)
c3x pricing sync --providers aws,azure

# Estimate without any network calls
c3x estimate --path . --offline

Self-hosted pricing API

C3X includes an independent pricing API that scrapes directly from AWS, Azure, and GCP public pricing APIs. Run it yourself for complete independence.

export C3X_SELF_HOSTED=true
export C3X_PRICING_API_ENDPOINT=http://localhost:4000
c3x estimate --path .

Core features

Cost estimates in your terminal

c3x estimate --path /code

Cost diffs before you deploy

c3x diff --path /code --compare-to baseline.json

PR comments in CI/CD

Post cost estimates automatically in pull requests. Works with GitHub Actions, GitLab CI, Bitbucket Pipelines, Azure Pipelines, Atlantis, and Spacelift.

Supported clouds and resources

C3X supports over 1,100 Terraform resources across AWS, Azure, and Google Cloud.

C3X can also estimate usage-based resources such as AWS S3, Lambda, and data transfer.

Roadmap

• Compare to real cloud bills — Validate estimates against AWS Cost Explorer / Azure Cost Management
• More IaC support — Pulumi, AWS CDK, Azure Bicep
• Historical cost tracking — Cost trends across commits and PRs
• IDE extensions — VS Code, JetBrains inline cost estimates

Community

Join our community Slack channel to learn more about cost estimation, ask questions, and connect with other users and contributors.

Contributing

We welcome contributions big and small. Please start by opening a thread in GitHub Discussions before submitting a PR. See our contribution guide for details.

License

Apache License 2.0