json to typescript interfaces

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Made by Maiyarasu S

Paste a sample API response and get TypeScript interfaces that describe it. The types are inferred from every item in your arrays, and everything runs in your browser.

How the types are inferred

Every object gets an interface named after the key that holds it, so a users array gives you a User interface. All items of an array are read together: a key that appears in some items but not others becomes optional (?), and a key whose values differ in type becomes a union such as string | null.

Objects with exactly the same shape share one interface instead of producing copies. Keys that are not valid identifiers are quoted, numbers are typed as number, and an empty array becomes unknown[] because there is nothing to infer from.

Getting good results

The interfaces are only as complete as the sample. Paste a response that includes the optional fields and null cases you care about, or several items in an array, and the types will cover them.

Use a query to generate types for one part of a document, choose 2 or 4 spaces of indentation, then copy the result or save it as a .d.ts file.

Questions

Does it write type or interface?

Objects become exported interfaces. When the top level is not an object, for example a plain array, the result is an exported type called Root.

Can it tell integers from decimals?

TypeScript has one number type, so both become number. The JSON Schema generator on this site does keep that difference.

Can it generate Zod or other schemas?

Not on this page. It writes TypeScript interfaces only.

Is my JSON sent anywhere?

No. The interfaces are generated in this page from the data you paste.

Related tools

help

QUERY (the prompt line)

Type a path or a filter after guest@json:~$. JSONPath and a jq-style subset both work, and the output shows only the result. Convert, copy and save then apply to that result.

$.users[0].nameone value by path. .users[0].name is the same thing
$["odd key"] $.ports[-1] $.ports[1:3]quoted keys, counting from the end, slices
$.users[*].name or .users[].nameevery item
$..namethat key at any depth
$.users[?(@.id > 1001 && @.sudo)]filter. Operators: == != < <= > >= && || !
.users[] | select(.sudo) | .namethe same idea in jq style, with pipes
.users | map(.name) | sortbuild a new list
[.users[] | select(.sudo)] | lengthcollect matches into an array, then count

Functions: length, keys, keys_unsorted, values, type, first, last, sort, sort_by(f), unique, reverse, flatten, add, min, max, to_entries, not, select(f), map(f), has(k), test(regex), contains(x), startswith(s), endswith(s).

TABS A AND B

stdin has two tabs. diff compares a with b by structure: key order is ignored, and an item inserted into an array counts once. validate checks tab a against the JSON Schema in tab b. Click any row in either list to open that spot in the tree.

REPAIR

When input is not valid JSON, the error view lists what auto-fix would change, line by line, before you apply it: comments, trailing or missing commas, single or smart quotes, bare keys, NaN and Infinity, hex and other number spellings, markdown code fences, JSONP wrappers, and input that was cut off. undo brings your original back.

VALUE HINTS

Links are clickable. Numbers that look like Unix times show the date. A badge after a string means it holds something: {…} JSON, jwt a token (decoded, never verified), b64 base64 text. Click the badge, or press Enter on the row, to expand it in place. A token pasted on its own, with or without Bearer in front, is offered as decode jwt instead of a parse error. Decoding never checks the signature.

KEYS

Ctrl+F or /search the output: the tree, or the text of minify, yaml, csv and ts. Enter next match, Shift+Enter previous. Write /pattern/ for a regular expression. In text output the keys and values buttons are off, and diff and validate switch to the tree
Alt+Qgo to the query prompt. Esc clears it
↑ ↓ ← →move in the tree. Left and right fold and unfold, with Shift they do the whole branch
Enter / Ctrl+C in the treefold or expand the row / copy the selected value
Ctrl+Enterformat stdin in place
Ctrl+Ssave the output as a file
Alt+C Alt+M Alt+S Alt+Fcopy, pretty or minify, sort keys, fold
Alt+1 Alt+2 Alt+Ttab a, tab b, next theme
Tab / Shift+Tab in stdinindent and outdent. Press Esc first to tab out of the box instead
Ctrl+Z / Ctrl+Shift+Z in stdinalso undo and redo format, auto-fix, load and clear

On a Mac, use Cmd for Ctrl and Option for Alt.

SAVED INPUT AND DISPLAY

Both tabs are kept in this browser between visits, however large. If the browser cannot keep an input, a note says so. The crt button turns scanlines and glow off. The page also drops them, and brightens dim text and borders, when your system asks for more contrast.

PRIVACY

Everything runs in this page, and the fonts are served with it. Nothing you paste is sent anywhere. A share link holds the compressed input inside the link itself, so anyone you send the link to can read it.

What you paste is also saved in this browser, so it is still here on your next visit. On a shared computer, or after pasting a secret, clear it. This removes both tabs and your settings from this browser.