tsconfig.json Checker

Validate tsconfig.json structure, flag unknown options, and surface common misconfigurations

Input

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Output

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What is tsconfig.json Checker

Last reviewed: April 18, 2026

JSON (JavaScript Object Notation) is a lightweight, human-readable data format used almost everywhere on the web for APIs, config files, and log output.

tsconfig.json Checker parses your tsconfig.json (with JSONC comment support), validates the structure of top-level keys and `compilerOptions`, and flags common misconfigurations that slow down builds or weaken type safety.

Typical findings include old targets (ES3/ES5), disabled strict mode, paths without baseUrl, and missing include/files arrays — which can cause TypeScript to scan the whole project by default.

Why use it

Audit tsconfig before opening a pull request.
Speed up slow TypeScript builds caused by wide includes.
Enforce strict-mode consistency across repos.
Catch typos in compilerOptions keys.
Onboard new developers with a safe default config.

Features

JSONC-aware (comments + trailing commas)
Checks top-level & compilerOptions shapes
Flags legacy targets, loose strictness
Warns about paths without baseUrl
All tsconfig.json work stays on your device

How to use tsconfig.json Checker

Paste tsconfig.json. Comments are OK.
Click Run. The checker validates structure and surfaces warnings.
Fix & re-check. Paste the updated config to confirm it's clean.

Example (before/after)

tsconfig.json

{
  "compilerOptions": {
    "target": "ES5",
    "strict": false,
    "paths": { "@/*": ["src/*"] }
  }
}

Report

✓ No blocking issues.

⚠ Warnings:
  • Target "ES5" is very old — prefer ES2020+ unless you ship to IE11
  • strict is disabled — consider enabling for stronger type safety
  • "compilerOptions.paths" without "baseUrl" may not resolve as expected
  • Neither "include" nor "files" is set — TypeScript will use the default ["**/*"] which can be slow

Common errors

Comments not supported

Some parsers choke on // comments.

Fix: This checker strips // and /* */ before parsing.

extends chains

`extends` isn't followed — only the current file is validated.

Fix: Paste each file separately if you need layered checks.

FAQ

Does it follow the extends chain?

No — it validates only the file you paste.

Does it support JSONC?

Yes — comments and trailing commas are handled.

What does 'strict is disabled' mean?

It means compilerOptions.strict is false — consider enabling for safer types.

Does it check every TypeScript option?

It covers the most common ones. New or experimental flags may be flagged as unknown.

Is input uploaded?

No — validation runs client-side.

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