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Developer Tools · head to head

ESLint vs Fly.io

ESLint logo

ESLint

Developer Tools

Find and fix problems in JavaScript code

From
Free
Free plan
Yes
Full reviewWebsite
Fly.io logo

Fly.io

Cloud

Deploy web applications globally

From
$29/month
Free plan
No
Full reviewWebsite

The short version

  • Only ESLint has a free tier, so it costs nothing to try first.
  • Each has a real cost: ESLint slow performance on large codebases compared to newer tools like Oxlint and Biome; 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
  • Prices and features above were last checked on 30 August 2026.

Where they differ

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

Attributes where ESLint and Fly.io differ
AttributeESLintFly.io
Starting priceFree$29/month
Pricing modelUnknownusage-based
Free tierYesNo
PlatformsBrowser-based JavaScript, Node.js, Any JavaScript environmentWeb, Api, Docker
CategoryDeveloper ToolsCloud
Founded20192020

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 ESLint

Nothing recorded that Fly.io does not also cover.

Only in Fly.io

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

What people use each for

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

ESLint

  • Statically analysing JavaScript and JSX to find problems before runtimenot Fly.io
  • Automatically fixing issues with syntax-aware rewritesnot Fly.io
  • Enforcing a consistent code style across a teamnot Fly.io
  • Running as a CI step to block non-conforming codenot Fly.io
  • Writing custom rules for project-specific conventionsnot Fly.io

Fly.io

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

Where each one falls short

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

ESLint

  • Slow performance on large codebases compared to newer tools like Oxlint and Biome
  • Complexity in configuration from scratch, particularly for TypeScript support
  • Limited built-in TypeScript support, requiring separate parsers and coordination with new TypeScript features

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

ESLint

Free

No published plan breakdown. See the ESLint 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 ESLint if

  • You want to start without paying.
  • You work on Browser-based JavaScript, Node.js, Any JavaScript environment.
ESLint 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 ESLint or Fly.io better?
Neither clearly leads. ESLint 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, ESLint or Fly.io?
ESLint has a free tier; the other does not. Paid plans start at Free for ESLint and $29/month for Fly.io.
Does ESLint or Fly.io run on more platforms?
ESLint runs on Browser-based JavaScript, Node.js, Any JavaScript environment. Fly.io runs on Web, Api, Docker.
Can I use ESLint for free?
Yes. ESLint has a free tier, so you can try it without paying. Fly.io starts at $29/month.
What is ESLint best used for?
ESLint is most often used for statically analysing javascript and jsx to find problems before runtime, automatically fixing issues with syntax-aware rewrites, enforcing a consistent code style across a team, running as a ci step to block non-conforming code. Of those, statically analysing javascript and jsx to find problems before runtime and automatically fixing issues with syntax-aware rewrites are not what Fly.io is typically brought in for.
What can ESLint do that Fly.io cannot?
Fly.io covers Global deployment, Docker support, Postgres databases, Redis support.

Answered from the vendors’ own pages

ESLint: Does ESLint automatically fix code issues?

Many problems ESLint finds can be automatically fixed via the --fix flag. ESLint fixes are syntax-aware so you won't experience errors introduced by traditional find-and-replace algorithms.

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
ESLint: How much does ESLint cost?

ESLint is completely free and open-source software maintained by the OpenJS Foundation. The project accepts voluntary donations from sponsors.

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
ESLint: Can I write custom ESLint rules?

Yes. You can develop custom rules that work alongside built-in functionality through ESLint's plugin system, allowing complete customization for your project needs.

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
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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