DevBolt
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How do I check my tsconfig for TypeScript 6.0 compatibility?

Paste your tsconfig.json and the tool checks for TS 6.0 breaking changes (removed ES3/ES5, outFile, AMD/UMD modules), deprecated options, and 9 changed defaults (strict:true, target:es2025, module:esnext). You get a readiness grade (A to F) with fix instructions for each issue. Everything runs in your browser.

Check legacy tsconfig
Input
{
  "compilerOptions": {
    "target": "ES5",
    "module": "commonjs",
    "moduleResolution": "node",
    "outFile": "./bundle.js"
  }
}
Output
Grade: D — 4 breaking changes

✗ target: "ES5" — removed in TS 6.0
  Fix: use "ES2020" or higher
✗ outFile — removed in TS 6.0
  Fix: use a bundler (esbuild, etc.)
✗ module: "commonjs" — deprecated
  Fix: use "NodeNext" or "ESNext"
⚠ moduleResolution: "node" — deprecated
  Fix: use "NodeNext" or "bundler"

TypeScript 6.0 Migration Checker

Paste your tsconfig.json and instantly see every breaking change, deprecated option, and default shift in TypeScript 6.0. Get a readiness grade, step-by-step fixes, and a corrected config. Supports JSONC (comments & trailing commas).

Samples:
Ctrl+Enter to analyze

What changed in TypeScript 6.0?

TypeScript 6.0 is the last JavaScript-based major release before the TypeScript 7.0 Go rewrite. It includes significant breaking changes to compiler defaults, removes legacy module systems, and deprecates options that will be hard-removed in 7.0.

Removed

  • target ES3/ES5
  • outFile option
  • module AMD/UMD/System
  • moduleResolution classic
  • esModuleInterop: false

Deprecated

  • moduleResolution: node
  • baseUrl as resolution root
  • downlevelIteration
  • alwaysStrict: false
  • module: none

New Defaults

  • strict: true
  • target: es2025
  • module: esnext
  • moduleResolution: bundler
  • types: [] (empty)

Build or update your config with the tsconfig.json Visual Builder. All analysis runs client-side — your config never leaves your device.

Tips & Best Practices

Pro Tip

Check for ES5 target and CommonJS modules first — these are removed

TypeScript 6.0 removes target: 'ES5' and module: 'commonjs' output modes. If your tsconfig.json uses these, you must migrate to ES2015+ target and ESM modules. This is the highest-impact breaking change and affects the most projects.

Common Pitfall

strict: true is now the default — existing projects may see new errors

Previously, strict mode was opt-in. In TS 6.0, it's the default. Projects that relied on implicit any types, unchecked null access, and loose function types will see hundreds of new errors. Add strict: false to your tsconfig.json explicitly if you can't fix them yet.

Real-World Example

Run the migration checker before upgrading TypeScript

Paste your tsconfig.json into DevBolt's TS6 Migration Checker before running npm install typescript@6. The readiness grade (A-F) and specific issue list tell you exactly what to fix. Grade A projects can upgrade immediately; grade D/F projects need preparation.

Security Note

The strict default improves security of TypeScript codebases

strict: true enables strictNullChecks (prevents null pointer errors), noImplicitAny (prevents untyped code), and strictFunctionTypes (prevents unsafe function assignments). These catches prevent common vulnerability patterns. Embrace the strict default rather than disabling it.

Frequently Asked Questions

What are the breaking changes in TypeScript 6.0?
TypeScript 6.0 introduces stricter defaults: strict mode enabled by default, isolatedDeclarations enforced for libraries, verbatimModuleSyntax replacing deprecated flags, and module resolution defaults changing to node16/nodenext. Some deprecated compiler options are fully removed. DevBolt's checker analyzes your tsconfig.json against these changes and reports which affect your project, providing a readiness grade and specific migration guidance.
How do I check if my TypeScript project is ready for TS 6.0?
Paste your tsconfig.json into DevBolt's analyzer. It examines compiler options against all known breaking changes and generates a readiness report with a letter grade (A through F). Each flagged item includes the breaking change description, your current setting, the recommended new setting, and step-by-step instructions. Issues are categorized by severity: critical (build failures), warnings (deprecated), and informational notes. Address critical issues first.
What is isolatedDeclarations and how does it affect TypeScript code?
isolatedDeclarations requires explicit type annotations on all exported functions, classes, and variables so declaration files can be generated without full type inference. This means adding return type annotations to all exported functions. The benefit is dramatically faster declaration file generation since tools can process files in parallel. Library authors publishing to npm are the primary audience. Build tools like tsgo leverage it for performance.

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