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Developer6 min readMay 22, 2026

The JSON formatter tab I keep open during deploy night

Finding trailing commas, duplicate keys, and escaped unicode when an API starts returning 500s.

TE

Toolncy Editorial

Practical file-tool guides · About the authors

Updated May 22, 2026

Production broke at 11 PM because a config JSON had a duplicate key. The second value silently won. Logs showed symptoms, not the typo. Paste into a formatter, collapse sections, duplicate keys stand out.

What I paste first

  • Raw API responses from curl — before assuming backend is wrong
  • Environment variable blobs someone swears is valid JSON
  • Webhook payloads from Stripe or GitHub with escaped newlines

Pretty-printing is not cosmetic. Indentation reveals nesting mistakes — an array closed too early, an object opened twice. I teach juniors to format before they grep.

Privacy note

Paste production JSON into tools that run locally. Browser formatters that upload payloads to a server are fine until they aren't.

Try it yourself

Open JSON Formatter — runs in your browser, no upload required.

Open JSON Formatter
json formatterdebuggingapidevtools
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