You copied some JSON, the parser exploded, and the error says something like:

Unexpected token ' in JSON at position 2

The culprit is almost always single quotes. Here's exactly why it happens
and how to fix it safely.

Why JSON is this strict about quotes

JSON was designed to be boring on purpose. Every parser, in every language,
agrees on what a string is because the format only allows double quotes.
No exceptions.

JavaScript makes this feel confusing. Single quotes are perfectly valid
in a JS object literal — but a JS object literal is not JSON. The moment
that payload hits JSON.parse(), the JSON rules win.

The three patterns people hit most

Invalid: all single quotes

{
  'name': 'StructKit',
  'mode': 'validator'
}

Invalid: even just one

{
  "name": 'StructKit',
  "mode": "validator"
}

One single-quoted value is enough to blow up the whole payload.

Valid: double quotes throughout

{
  "name": "StructKit",
  "mode": "validator"
}

What the error looks like in each runtime

The Python trap

Python is the most common case. Dict literals use single quotes naturally,
so it's easy to forget that json.loads parses strict JSON, not Python syntax.

# ❌ This fails
payload = "{'name': 'StructKit'}"
json.loads(payload)  # JSONDecodeError

# ✅ This works
data = {"name": "StructKit"}
payload = json.dumps(data)
json.loads(payload)

How to fix it without breaking your data

A blind find-and-replace from ' to " is how you turn one error into two.
Apostrophes inside real text — like "user's name" — are valid and should
stay as they are. Replace only the quotes acting as JSON delimiters.

This is valid JSON:

{
  "message": "It's valid JSON",
  "owner": "Alex's tool"
}

If your payload is still failing after fixing the quotes, a JSON validator
that shows you the exact line and column helps a lot. I built one at
structkit.dev alongside a few reference guides
for exactly these kinds of errors.