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What is JSON Master?

An editor for JSON documents, built around what you actually do all day with JSON: find the value, copy its path, copy the branch, and work out what a field really contains. Everything you open and save is an ordinary .json file — there is no project format and nothing to import. The app is written natively for Apple platforms, with no web view inside, and it needs no account and no internet connection.

Tree, source, or both?

The document is shown two ways, and both are the same file. The tree is for reading and restructuring, the source for fixing what does not parse, and Both shows them side by side, with the source following the tree selection and the inspector following the caret.

On Mac the views are in the segmented control in the toolbar (⌘1, ⌘2, ⌘3). On iPad they are in the "…" menu; on iPhone, also in the switch at the right of the status bar. Both needs width, so it is offered on Mac and iPad but not on iPhone.

My file won't parse. Now what?

It still opens — that is usually why you opened an editor at all. The tree shows the lines around the error with a caret under the exact column, and Jump to error takes you there in the source. The status bar reports the line and column too, and tapping it does the same. Syntax colouring keeps working on a broken document, which is exactly when it helps most: a string that stays green past where it should have ended shows you the missing quote.

Can it fix "almost JSON"?

Yes. When the text is relaxed JSON — comments, trailing commas, single quotes, unquoted keys — the app offers Repair JSON and rewrites it as strict JSON in one step, which a single undo takes back. A log dump where every line is a value of its own is recognised as JSON Lines and offered as an array. Pasting almost-JSON into an empty document fixes it on paste.

If you work with such files all the time, turn on Allow comments and trailing commas in Settings → Editing, and they open as they are. It is off by default on purpose: an editor should say plainly whether a file is valid JSON.

Does it handle large files?

Anything over a megabyte is parsed in the background while the window shows how far it has got, so the app stays responsive. Huge arrays stay collapsed until you open them.

What is the command palette?

Every command by name, plus a fuzzy jump to any node. Press ⌘K on Mac or iPad with a keyboard, or choose Command Palette at the top of the "…" menu on iPhone and iPad. Type a few letters of a path — adrcity finds customer.address.city — or the name of a command, including theme and view switches. Typed in the wrong keyboard layout? It still finds what you meant.

How does search work?

⌘F on Mac, the magnifier in the toolbar on iPhone, and the "…" menu on iPad. Search keys, values or both, with case sensitivity and whole-value matching. Branches that contain a match open by themselves, Return or the arrows step through the matches with a live "3 of 12", and closing the search brings the whole document back.

How do I get back to where I was?

The breadcrumbs above the tree show the path to the selected node, and each segment is clickable. After any jump — from the palette, a query, the summary or the breadcrumbs — Back and Forward (⌘[ and ⌘]) retrace your steps.

A three-thousand-line response. How do I see one part of it?

Show only this branch in a row's menu (or Focus in the inspector) narrows the tree to that subtree until you leave it. The Tree section of the "…" menu has Expand all, Collapse all and Expand to level 1–6, and Settings → General decides how many levels a document opens with. Collapsed objects show their first keys, { id, name, email, … }, so you often need not open them at all.

How do I copy a path?

Select a node and the inspector shows its path in six notations — dot, JSONPath, brackets, jq, Swift and JSON Pointer — each with its own copy button. The one you choose as Path notation in Settings → Copying is used by Copy path (⇧⌘C); Copy path as in a row's menu still offers the rest.

A row's menu is a right-click on Mac and a long press on iPhone and iPad. On iPhone the floating bar at the bottom puts copy and copy path one tap away.

How do I copy a value, or a whole branch?

Copy value in the row's menu, or ⌘C with the tree focused. On an object or an array it copies the entire subtree, formatted; Copy minified copies it on one line. There is also Copy key, and Copy key and value, which gives you the pair ready to paste into a neighbouring object.

Why did my copied string lose its quotes?

Because a copied id usually goes straight into a request, where the quotes are in the way. If you would rather have the JSON literal, turn off Copy strings without quotes in Settings → Copying.

How do I edit a value or a key?

Select the node: the inspector lets you change the value, rename the key or change the type, keeping what can be kept — a number becomes its own literal as a string, "true" becomes a boolean. Its buttons copy, focus, show the node in the source, duplicate and delete, and a row's menu adds children. Every edit is one undo step.

Why did my formatting change after I edited in the tree?

Because the text is the source of truth and the tree is its parse. A file you have not touched is saved back byte for byte — foreign indentation, key order and all. An edit made in the tree has to be written out again, and it is written with your indentation setting. One undo brings the old text back.

Where are the document tools?

In the "…" menu. Its Document section holds Format, Minify, Sort keys (A → Z or Z → A, recursively; array order is never touched), Expand embedded JSON, Remove empty values and Remove duplicate keys — plus Convert JSON Lines into an array, which appears only when the text is JSON Lines.

Tools holds Query, Summary, Compare, Generate types and Decode a token. On Mac they have their own toolbar button and are also in the JSON menu; on iPhone and iPad they are a section of the "…" menu.

What can the tools do?

• Query — JSONPath with keys, indices, slices, [*], recursive .. and conditions such as [?(@.type=='book')]. Results update as you type; tap one to jump to it.
• Summary — node and key counts, depth, size and types, plus findings worth a look: duplicate keys, unsafe integers, strings holding JSON. Each one jumps to its node.
• Compare — against another file or the clipboard, by structure: reordered keys are not a difference, and reindentation does not mark the whole file as changed.
• Generate types — Swift Codable, TypeScript interfaces or JSON Schema. Fields missing from some array elements become optional.
• Decode a token — paste a JWT and read its header and payload as JSON.

What is the inspector telling me about a value?

It recognises what the value really is: Unix timestamps become a readable date, JWT tokens are decoded with their expiry checked, base64 is decoded when the result is readable text, and ISO 8601 dates and URLs are named as such. It shows string length in characters and bytes, and flags integers beyond 2⁵³ — the usual reason an id breaks in JavaScript.

Is a JWT signature verified?

No. The token is decoded so you can read it; verifying the signature would need the issuer's key, so the app does not pretend to do it and says so on screen. Decoding happens on your device, and nothing is sent anywhere.

What do the "1/2" marks in the tree mean?

Duplicate keys. JSON permits the same key twice in one object and most parsers quietly keep one of them; here every occurrence gets its own row, marked 1/2, 2/2, so you can see which value is which. The object that contains them is marked too, and the inspector explains the finding. Remove duplicate keys keeps the last occurrence, which is what most parsers would have given you.

Which files can it open?

.json, .jsonc, .jsonl, .ndjson and .geojson. A file is saved back in place in its own format, so there is no forced "Save as".

On Mac, if your .json files still open in another app, select one in Finder, press ⌘I, choose JSON Master under Open with and click Change All.

Where are my files stored?

Wherever you save them. JSON Master is a standard document-based app and uses the system file browser: Files on iPhone and iPad, Finder on Mac, including iCloud Drive and any other provider you have connected. On iPhone and iPad the app's own folder is under Browse → On My iPhone (or iPad) → JSON Master.

How do I get the document out?

Export in the "…" menu writes formatted JSON, minified JSON or a CSV table; Copy the whole document next to it puts the text on the clipboard. CSV needs an array of objects: nested objects become address.city columns and arrays stay as JSON in the cell. If the shape is not a table, the app says so instead of inventing columns.

Where is Settings, and what is in it?

On Mac, ⌘, or the JSON Master menu; on iPhone and iPad, at the bottom of the "…" menu.

• General — interface language and how many tree levels a document opens with.
• Appearance — theme, text size (9–22 pt), tree density, type icons, item counts, indent guides and previews of collapsed objects, with a live preview.
• Editing — indentation (2 spaces, 4 spaces or a tab), escaping non-ASCII as \u, and lenient parsing.
• Copying — the default path notation and copying strings without quotes.

Can I change the look?

There are four themes: Midnight (the default, deep blue-black with a periwinkle accent), Graphite (neutral grey and system blue), Amber CRT (the original phosphor look) and Daylight, a light theme for bright rooms and projectors. Switch in Settings → Appearance or from the command palette; the change is immediate. Themes do not follow the system appearance on purpose: the one you pick is the one you get, window chrome included.

Can I change the language?

Yes. The app speaks English, German, French, Ukrainian, Spanish, Japanese and Portuguese. By default it follows your device language, falling back to English. Change it in Settings → General and the interface switches immediately; it is the same setting as the app's language in the system — iOS Settings → Apps → JSON Master → Language, or System Settings → General → Language & Region → Applications on Mac.

Does it need an internet connection?

No. The app works entirely offline and makes no network requests at all. See the privacy policy.

System requirements

iPhone with iOS 18 or later, iPad with iPadOS 18 or later, Mac with macOS 15 or later, or Apple Vision Pro with visionOS 2 or later.

Which keyboard shortcuts are there?

On Mac, and on iPad with a hardware keyboard:

⌘K	Command palette
⌘F	Search
⌘J	Query
⌘1 ⌘2 ⌘3	Tree, source, both
⌥⌘I	Show or hide the inspector
⇧⌘C	Copy path
⌘[ ⌘]	Back, forward
⇧⌘I ⇧⌘M	Format, minify
⌥⌘→ ⌥⌘←	Expand all, collapse all
⌘Z ⇧⌘Z	Undo, redo
⌘,	Settings (Mac)

In the tree: the arrows move the selection (→ opens, ← closes or climbs), Space toggles a branch, Return shows the node in the source, ⌘C copies its value and Delete removes it.