JSON Validator & Formatter: How to Fix Invalid JSON Fast (Without Installing Anything)

Sujal Khatri — Fri, 16 Oct 2026 21:04:28 +0000

JSON is everywhere — APIs, config files, package.json — and it breaks in the most annoying ways. Here are the 5 errors I see most often, and the fastest ways to find and fix them without installing anything.

1. Trailing commas

{
  "name": "Sujal",
  "city": "Jaipur",
}

That comma after "Jaipur" kills the whole file. JSON does not allow trailing commas, period. Delete it.

2. Single quotes instead of double quotes

{ 'name': 'Sujal' }

Looks fine, is not JSON. Keys AND string values must use double quotes:

{ "name": "Sujal" }

3. Unquoted keys

{ name: "Sujal" }

Valid JavaScript object, invalid JSON. Quote every key.

4. Comments

{
  // user details
  "name": "Sujal"
}

JSON has no comments. If you need them, use JSONC in your editor — but strip them before sending to an API.

5. NaN, Infinity, undefined

{ "score": NaN }

These are JavaScript things, not JSON things. Use null or a number.

The fastest ways to validate

Browser console (zero setup): paste your JSON into JSON.parse('...'). The error message tells you the exact character position where it broke. That's usually enough.

Python (already on most machines):

echo '{"a":1,}' | python3 -m json.tool

It pretty-prints valid JSON and points at the error for invalid JSON.

jq (if you live in the terminal):

echo '{"a":1}' | jq .

Formatting: pick one style and stick to it

2-space indent is the most common. Tabs are fine too. What matters is consistency — mixed indentation makes diffs unreadable and code reviews painful.

A real before/after

Before:

{
  'users': [
    { name: 'Amit', age: 24, },
    { name: 'Priya', age: 29, },
  ],
}

After:

{
  "users": [
    { "name": "Amit", "age": 24 },
    { "name": "Priya", "age": 29 }
  ]
}

Four fixes: quotes, keys, trailing commas, and it's done.

I got tired of switching between five different sites for this kind of work, so I built BulkTextKit — 15 free text tools in the browser, including a JSON formatter/validator that points at the exact error. Pro (batch processing, presets, CSV export) is $9 until Oct 19: https://bulktextkit.gt.tc

I built 15 free text tools with plain PHP and zero APIs — here's what I learned

Sujal Khatri — Wed, 14 Oct 2026 17:34:12 +0000

This week I launched a new product: BulkTextKit, a set of 15 free text tools — word counter, case converter, JSON formatter/validator, regex tester, slug generator, and more — that run entirely in your browser. No signup, no uploads, no tracking. I'm a solo maker in India, I build with plain PHP + MySQL, and I made one unusual choice on purpose: zero third-party APIs. Everything the tools do happens in client-side JavaScript; the server only renders pages and handles the Pro license flow through PayPal. In this post I'll walk through why I chose that architecture, how the build went, and the one-time pricing model I'm betting on instead of yet another subscription.

The problem I kept hitting

Every day I run into the same tiny text chores: counting words in client copy, converting a heading to title case, stripping duplicate lines from a messy list, or checking whether a snippet of JSON is actually valid. These jobs take a minute each, but they pile up when you work with words all day.

The free tools I found online were scattered across dozens of ad-heavy pages, and most of them sent my text to some server I knew nothing about. I stopped trusting them for anything sensitive, which meant I kept doing these chores by hand or wiring up throwaway scripts. That friction is the problem BulkTextKit exists to erase: one fast page, fifteen tools, nothing leaves your browser.

Why PHP + zero APIs

One deliberate decision shaped the whole product: zero third-party APIs. No API keys means nothing to leak, nothing to rotate, and no third-party service that can be shut down, rate-limited, or bought and sunsetted underneath me.

It also means the site runs on cheap shared hosting with plain PHP and MySQL. There is no build pipeline, no framework to keep updated, and no SDK that can break a deploy. For a solo maker in India, boring infrastructure is a feature, not a compromise.

How the tools work

All fifteen tools run 100% in browser JavaScript — Word Counter, Case Converter, Remove Duplicate Lines, JSON Formatter & Validator, Regex Tester, Slug Generator, Lorem Ipsum Generator, Text Diff, CSV to Columns, Remove Line Breaks, Word Frequency Counter, Base64 Encoder/Decoder, Markdown Table Generator, Strip HTML, and Password Generator.

PHP only renders the pages and handles the Pro license flow, including the PayPal IPN handshake that activates a purchase. Your text never touches my server, which is exactly the point: you can paste client work into these tools without wondering where it went.

The business model

All fifteen tools are free forever — that is the product, not a trial. Pro is a one-time payment of $9 during the 72-hour launch offer (regular price $19), unlocking bulk/batch mode for up to 50 texts at once, saved presets for repeat tasks, and CSV export. Checkout is via PayPal, and every purchase is covered by a 7-day money-back guarantee.

I am betting on one-time pricing instead of yet another subscription because these are small utilities, not a platform. The launch offer is live now at BulkTextKit — try the free tools and tell me: which tool should I add next?

What I'd do differently

If I built this again, I would start marketing much earlier. I waited until launch week to talk about it publicly, which meant I launched to no audience at all. I would also ship smaller: instead of polishing fifteen tools before telling anyone, I would have launched with five and let feedback pick the rest.

Both lessons point the same way: build in the open from day one. I am starting now, so expect to see more of the process, not just the finished product.

DEV Community: Sujal Khatri