Blue-Green vs Canary Deployments: What's the Difference?

When you deploy new versions of your application, you want to minimize downtime and risk. Two common strategies are Blue-Green and Canary deployments. Here's how they differ.

Blue-Green Deployment

You maintain two identical production environments: Blue (current) and Green (new). You deploy the new version to Green while Blue continues serving all traffic. When Green is ready and tested, you switch all traffic from Blue to Green in one go—usually via a load balancer or router. If something goes wrong, you switch back to Blue immediately.

Pros: Instant rollback, zero-downtime releases, simple to reason about. Cons: Requires double the infrastructure; everyone gets the new version at once, so a bad release affects all users.

Canary Deployment

You deploy the new version alongside the old one, but only a small percentage of traffic (e.g. 5–10%) is sent to the new version. The rest stays on the old one. You monitor metrics (errors, latency, conversions). If everything looks good, you gradually increase traffic to the new version until 100%. If not, you route traffic back to the old version.

Pros: Limits blast radius; you validate the new version with real users before full rollout. Cons: More complex (routing, feature flags, metrics); rollout is gradual so it takes longer.

Which to use?

Use Blue-Green when you want a clean cutover and fast rollback with simpler setup. Use Canary when you want to reduce risk by testing the new version with a subset of users before committing fully.