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Developer Tools · head to head

ESLint vs Unleash

ESLint logo

ESLint

Developer Tools

Find and fix problems in JavaScript code

From
Free
Rated
-
Full reviewWebsite
Unleash logo

Unleash

Software Development

Open-source feature flag and experimentation service

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: ESLint slow performance on large codebases compared to newer tools like Oxlint and Biome; Unleash the Pay-As-You-Go plan is priced per seat, which can get costly for larger teams.

Where they differ

Only the attributes on which ESLint and Unleash actually diverge.

Attributes where ESLint and Unleash differ
AttributeESLintUnleash
Pricing modelUnknownfreemium
PlatformsBrowser-based JavaScript, Node.js, Any JavaScript environmentweb, api, linux
CategoryDeveloper ToolsSoftware Development
Founded2019Unknown

Identical on both: starting price (Free), free tier (Yes), 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 Unleash does not also cover.

Only in Unleash

  • Feature flags
  • A/B/n testing
  • Custom targeting
  • SDKs
  • SSO
  • Audit logs

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 Unleash
  • Automatically fixing issues with syntax-aware rewritesnot Unleash
  • Enforcing a consistent code style across a teamnot Unleash
  • Running as a CI step to block non-conforming codenot Unleash
  • Writing custom rules for project-specific conventionsnot Unleash

Unleash

  • Gradual and progressive feature rolloutsnot ESLint
  • Running A/B/n experiments tied to flagsnot ESLint
  • Self-hosting feature management for compliance needsnot ESLint
  • Enterprise SSO-controlled feature flag governancenot 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

Unleash

  • The Pay-As-You-Go plan is priced per seat, which can get costly for larger teams.
  • Self-hosted Enterprise requires a minimum of 5 seats and an annual contract.
  • Additional API traffic beyond the included quota is billed per million requests.
  • Advanced SLAs and dedicated customer success are reserved for the custom Enterprise tier.

Pricing, plan by plan

ESLint

Free

No published plan breakdown. See the ESLint review.

Unleash

Free
  • Pay-As-You-Go$75/month
    • Cloud-hosted
    • 53M API requests/month included
    • Unlimited feature flags, projects and environments
  • Custom Enterprise$undefined/mo
    • Cloud, self-hosted or hybrid
    • Premium support options
    • 99.99% uptime SLA

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 Unleash if

  • You need feature flags.
  • You want to start without paying.
  • You work on web, api, linux.
  • You also want a/b/n testing.
Unleash review

Questions people ask

Is ESLint or Unleash better?
Neither clearly leads. ESLint starts at Free and Unleash at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, ESLint or Unleash?
ESLint starts at Free and Unleash at Free.
Does ESLint or Unleash run on more platforms?
ESLint runs on Browser-based JavaScript, Node.js, Any JavaScript environment. Unleash runs on web, api, linux.
Can I use ESLint for free?
Both have a free tier, so you can try either at no cost before committing.
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 Unleash is typically brought in for.
What can ESLint do that Unleash cannot?
Unleash covers Feature flags, A/B/n testing, Custom targeting, SDKs.

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
Unleash: What does Unleash cost?

Unleash offers a Pay-As-You-Go cloud plan at $75/seat/month with a 14-day free trial, plus a custom-priced Enterprise plan for self-hosted or hybrid deployments.

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
Unleash: How is usage metered?

The Pay-As-You-Go plan includes 53M API requests per month, with additional traffic billed at $5 per million requests thereafter.

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
Unleash: What does Unleash integrate with, and is there an API?

Unleash provides an API and 25+ official SDKs across languages, along with SSO integrations via SAML 2.0 and OpenID Connect.

Source
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