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Technology · head to head

Docker vs Fly.io

Docker logo

Docker

Technology

Accelerate how you build, share, and run applications

From
Free
Rated
-
Full reviewWebsite
Fly.io logo

Fly.io

Cloud

Deploy web applications globally

From
$29/month
Rated
-
Full reviewWebsite

The short version

  • Only Docker has a free tier, so it costs nothing to try first.
  • Each has a real cost: Docker shared kernel creates security vulnerabilities when containers share the same OS kernel that can bypass container isolation; Fly.io egress is priced by destination region, from $0.02 per GB in North America and Europe to $0.12 per GB for Africa and India, so the same traffic costs six times more depending on where users are
  • They diverge on capability: Docker covers Container runtime, Fly.io covers Global deployment.

Where they differ

Only the attributes on which Docker and Fly.io actually diverge.

Attributes where Docker and Fly.io differ
AttributeDockerFly.io
Starting priceFree$29/month
Pricing modelUnknownusage-based
Free tierYesNo
PlatformsLinux, macOS, WindowsWeb, Api, Docker
CategoryTechnologyCloud
Founded20102020

Identical on both: user rating (Not yet rated).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Docker

  • Container runtime
  • Docker Desktop
  • Docker Hub
  • Docker Compose
  • Container images
  • Dockerfile
  • Docker Swarm
  • BuildKit

Only in Fly.io

  • Global deployment
  • Docker support
  • Postgres databases
  • Redis support
  • Auto-scaling
  • Health checks
  • Backups
  • Monitoring

Both cover

  • GitHub

What people use each for

The jobs each tool is most often brought in to do.

Docker

  • Application containerizationnot Fly.io
  • Microservicesnot Fly.io
  • CI/CD pipelinesnot Fly.io
  • Development environmentsnot Fly.io
  • Cloud migrationnot Fly.io

Fly.io

  • Deploying containerised applications close to users across regionsnot Docker
  • Running full stack apps and databases on managed machinesnot Docker

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Docker

  • Shared kernel creates security vulnerabilities when containers share the same OS kernel that can bypass container isolation
  • Daemon socket exposure grants full root access to the host if compromised
  • Requires careful secrets management - credentials embedded in images or environment variables are easily harvested by attackers
  • Resource management complexity - misbehaving or compromised containers can consume all resources causing denial of service
  • Orchestration complexity - Docker Swarm is less capable than Kubernetes, requiring external tools for production deployments

Fly.io

  • Egress is priced by destination region, from $0.02 per GB in North America and Europe to $0.12 per GB for Africa and India, so the same traffic costs six times more depending on where users are
  • Stopped machines still bill at $0.15 per GB of root filesystem a month, so a paused service is not a free one
  • Volumes are billed on provisioned capacity rather than usage, at $0.15 per GB a month
  • Reservation discounts of 40% require paying a year up front, from $36 to $1,440
  • Fly Kubernetes is a separate $75 a month per cluster
  • Dedicated IPv4 addresses are $2 a month each

Pricing, plan by plan

Docker

Free

No published plan breakdown. See the Docker review.

Fly.io

$29/month
  • Pay-as-You-Go$null/mo
    • Micro VMs and persistent storage charged by usage
    • FlyCTL CLI
    • Unlimited users and organizations
  • Serious Support$29/month
    • Access to dedicated engineering team
    • All Pay-as-You-Go features
  • Machine Reservation Blocks$null/mo
    • 40% discount on machine usage
    • Requires upfront payment for savings
  • Compliance Package$99/month
    • HIPAA compliance
    • BAAs
    • SOC2 documentation

Which should you pick?

Choose Docker if

  • You need container runtime.
  • You want to start without paying.
  • You work on Linux, macOS, Windows.
  • You also want docker desktop.
Docker review

Choose Fly.io if

  • You need global deployment.
  • You work on Web, Api, Docker.
  • You also want docker support.
Fly.io review

Questions people ask

Is Docker or Fly.io better?
Neither clearly leads. Docker starts at Free and Fly.io at $29/month, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Docker or Fly.io?
Docker has a free tier; the other does not. Paid plans start at Free for Docker and $29/month for Fly.io.
Does Docker or Fly.io run on more platforms?
Docker runs on Linux, macOS, Windows. Fly.io runs on Web, Api, Docker.
Can I use Docker for free?
Yes. Docker has a free tier, so you can try it without paying. Fly.io starts at $29/month.
What is Docker best used for?
Docker is most often used for application containerization, microservices, ci/cd pipelines, development environments. Of those, application containerization and microservices are not what Fly.io is typically brought in for.
What can Docker do that Fly.io cannot?
Docker covers Container runtime, Docker Desktop, Docker Hub, Docker Compose. Fly.io covers Global deployment, Docker support, Postgres databases, Redis support. Both handle GitHub.

Answered from the vendors’ own pages

Docker: What is Docker pricing?

Docker offers a freemium model with Docker Personal free, Docker Pro at $11/user/month, Docker Team at $16/user/month, and Docker Business at $24/user/month. Each tier includes Docker Desktop, Docker Hub, and Docker Scout with different usage limits.

Source
Fly.io: Is there a free tier for Fly.io?

Fly.io does not advertise a free tier. The base plan is pay-as-you-go with usage-based pricing for Micro VMs and persistent storage. All users get FlyCTL CLI, unlimited organizations, private networking, SSO, ACLs, and scoped tokens.

Source
Docker: Can I use Docker in production?

Yes. Docker is used extensively in production environments. However, for container orchestration at scale, Kubernetes is typically paired with Docker to automate deployment, scaling, and management across clusters.

Source
Fly.io: How much does Fly.io Serious Support cost?

Serious Support costs 29 USD per month and provides access to a dedicated engineering team while maintaining all pay-as-you-go features for Micro VMs and storage.

Source
Docker: What are the main security concerns with Docker?

Key security risks include container breakout vulnerabilities through shared kernel exploits, daemon socket exposure that grants root access if compromised, weak isolation between containers, and credential leakage if secrets are embedded in images.

Source
Fly.io: What does Fly.io Compliance Package include?

The Compliance Package is 99 USD per month and includes HIPAA compliance, BAAs, and SOC2 documentation for organizations requiring compliance certifications.

Source
Docker: Does Docker integrate with CI/CD systems?

Yes. Docker integrates with Jenkins, GitHub, and other CI/CD systems. The typical workflow involves GitHub repositories triggering automated builds in Jenkins, which prepare Dockerfiles and push images to Docker Hub for deployment.

Source
Fly.io: Does Fly.io offer discounts for upfront commitment?

Yes, Fly.io offers Machine Reservation Blocks with 40% discount on machine usage. This requires upfront payment but applies savings on infrastructure costs.

Source
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