Offline JSON formatter for Mac: keep private payloads local

Use an offline JSON formatter when the input is private, work-related, or hard to sanitize. Use a web formatter for public examples, fake data, documentation snippets, and quick throwaway samples.

TeenyTool includes a local JSON Formatter in its Mac menu bar toolbox. Paste JSON, choose Pretty or Compact, see validity immediately, copy the output, and move on without uploading the payload to a website.

Quick comparison

What not to paste into a web formatter

Do not paste production payloads, support exports, logs, JWTs, API responses with customer fields, internal feature flags, database IDs, addresses, emails, or anything copied from a private admin screen.

The problem is not JSON itself. RFC 8259 defines JSON as a lightweight text data interchange format. The problem is the data inside it. A formatter only changes whitespace, but the website still receives the text if it is not fully local in your browser, and most users are not going to audit the site's JavaScript first.

Even when a site says it works client-side, the safer default is simple: if the JSON would not belong in a public issue, keep it in a local app.

How TeenyTool formats JSON

The TeenyTool JSON Formatter has two modes: Pretty and Compact. Pretty mode emits readable indentation and sorts object keys. Compact mode removes the extra whitespace while keeping valid JSON structure.

The implementation validates input with Apple's JSONSerialization, then tokenizes the original string and re-emits it. That second step matters. Number tokens are preserved as text, so a value such as 149.99 does not turn into a floating-point artifact during formatting.

The output panel includes a one-click copy action through the macOS pasteboard. Nothing about normal JSON formatting needs the network.

The adjacent tools matter

JSON rarely travels alone. The useful local workflow is not just formatting one blob. It is moving through related cleanup without opening five separate sites.

• JSON Diff compares two objects or arrays and highlights added, removed, changed, nested, and unchanged values.
• YAML to JSON and CSV to JSON handle common handoff formats when data comes from config or spreadsheets.
• JWT Decoder decodes token header and payload locally, which is exactly where that job belongs.
• Base64 Codec and URL Codec cover the encoding layer around many copied API snippets.
• Hash Generator and UUID Generator sit nearby when you need test identifiers or checksums.

This is why a menu bar toolbox can beat a single-purpose formatter. You start with JSON, then realize the value inside it is Base64, the token is a JWT, the timestamp needs converting, or the second payload needs a diff.

When a local formatter is not enough

Use a deeper tool when you need schema validation, JSONPath querying, API replay, request signing, collection management, or team-shared API documentation. A small formatter should not pretend to be an API client.

Use your editor when the JSON already lives in a repo. Editor formatters are excellent for files. TeenyTool is stronger for scratch payloads copied from tickets, chats, logs, browsers, and support tools.

Use the command line when you want a scriptable pipeline. jq is still the better answer for repeatable transforms, filtering, and automation. The menu bar is for fast manual work.

Setup and workflow

1. Open teenytool from the menu bar.
2. Search for "JSON" or open the Developer category.
3. Choose JSON Formatter.
4. Paste the payload into the left panel.
5. Choose Pretty or Compact.
6. Copy the output from the right panel.

If JSON work is part of your normal day, add JSON Formatter, JSON Diff, JWT Decoder, and Base64 Codec to favorites. TeenyTool supports up to 12 favorites and lets you assign shortcuts to favorite tools from settings.

Privacy and network exceptions

TeenyTool is local-first, not magic. Normal text, developer, color, image, PDF, clock, math, and random tools run on the Mac. The product's network exceptions are license validation, update checks, IP Address, and DNS Lookup. Those exceptions are explicit because vague privacy claims are not useful.

The same rule appears in the TeenyApps hub guide to local Mac utilities vs online tools: keep private, repeated, easy-on-device work local; use the web when the job genuinely depends on the web.

Common questions

Is TeenyTool's JSON formatter offline?

Yes. The JSON Formatter runs locally in the Mac app. TeenyTool uses the network for license validation, update checks, IP Address, and DNS Lookup, not for normal JSON formatting.

Does TeenyTool preserve large JSON numbers?

TeenyTool validates JSON with JSONSerialization, then tokenizes the original input and re-emits number tokens verbatim so values are not rounded by Double conversion during formatting.

When is an online JSON formatter safe enough?

Use an online formatter for public examples, fake data, or documentation snippets. Keep production payloads, support logs, JWTs, internal IDs, and customer data in a local tool.

Sources checked

• TeenyTool feature claims were checked against the local homepage and source files for the tool catalog, JSON Formatter, JSON Diff, YAML/CSV conversion, favorites, shortcuts, and pasteboard copy behavior.
• RFC 8259 for the JSON data interchange format.
• Apple NSPasteboard documentation for macOS pasteboard behavior.