InterLAB tools · JSON ↔ YAML ↔ CSV · line-level errors · TypeScript

JSON, YAML and CSV converter

Paste your data and the result appears instantly. The format is detected for you, errors show the line, column and a snippet, and the tree helps you find the right path. Everything runs on your device.

Free, no sign-up

How the converter works

Format detection
Text starting with { or [ is JSON. Rows with the same number of fields separated by commas, semicolons, tabs or | are CSV/TSV. Anything else is read as YAML. You can also pick the format yourself.
Parsing with exact error location
JSON is parsed by a dedicated RFC 8259 parser: an error shows the line, column, a snippet with a ^ marker and a plain explanation. YAML uses the yaml library (versions 1.2 and 1.1), and CSV follows RFC 4180 with quotes and line breaks inside fields.
Conversion
Nested objects become user.name and tags[0] columns in CSV and are rebuilt when reading. You can sort keys, change the indent, minify, escape non-ASCII or get TypeScript types from a sample.
Tree and filter
The tree shows the structure; clicking a key copies a path such as $.users[0].name. A path filter (users[*].id, $.owner) keeps only the matches in the result.

Standards and traps

JSON — RFC 8259; YAML — specifications 1.2.2 and 1.1; CSV — RFC 4180; TSV — tab-separated (quoted only when a value contains a tab or line break).

The most common YAML trap is the version gap. Kubernetes, Ansible and PyYAML often read YAML by 1.1 rules, where “no” is false and “0755” is octal. The tool reads YAML 1.2 by default and warns about each such value with its line number; YAML output quotes these strings.

Value	YAML 1.2	YAML 1.1
no	"no"	false
yes	"yes"	true
on	"on"	true
off	"off"	false
0755	755	493
1:30	"1:30"	90
2026-10-14	"2026-10-14"	"2026-10-14T00:00:00.000Z"

YAML 1.2: "no"
YAML 1.1: false

yes

YAML 1.2: "yes"
YAML 1.1: true

YAML 1.2: "on"
YAML 1.1: true

off

YAML 1.2: "off"
YAML 1.1: false

0755

YAML 1.2: 755
YAML 1.1: 493

1:30

YAML 1.2: "1:30"
YAML 1.1: 90

2026-10-14

YAML 1.2: "2026-10-14"
YAML 1.1: "2026-10-14T00:00:00.000Z"

The same “key: …” in YAML 1.2 and 1.1 (parsed by the tool)

Format	File	MIME	What it does
JSON	.json	application/json	RFC 8259; indent 2/4/tab, minify, sort, \uXXXX
YAML	.yaml	application/yaml	YAML 1.2; documents with ---, quotes for yes/no/on/off
CSV	.csv / .tsv	text/csv	RFC 4180; column paths, array strategies, formula protection
TypeScript	.ts	text/typescript	interface or type inferred from the data
Query string	.txt	text/plain	a[b]=1&t[0]=x, encoded with encodeURIComponent

JSON

File: .json
MIME: application/json
What it does: RFC 8259; indent 2/4/tab, minify, sort, \uXXXX

YAML

File: .yaml
MIME: application/yaml
What it does: YAML 1.2; documents with ---, quotes for yes/no/on/off

CSV

File: .csv / .tsv
MIME: text/csv
What it does: RFC 4180; column paths, array strategies, formula protection

TypeScript

File: .ts
MIME: text/typescript
What it does: interface or type inferred from the data

Query string

File: .txt
MIME: text/plain
What it does: a[b]=1&t[0]=x, encoded with encodeURIComponent

Output formats

Code	Message
empty	The input is empty.
unexpected-end	Unexpected end of data: a closing bracket, quote or value is missing.
unexpected-char	Unexpected character: a value was expected here (a double-quoted string, number, true, false, null, object or array).
unterminated-string	Unterminated string: no matching quote before the end of the line.
bad-escape	Invalid escape sequence. JSON allows \" \\ \/ \b \f \n \r \t and \uXXXX.
control-char	Control character inside a string: write tabs and line breaks as \t and \n.
bad-number	Invalid number: JSON has no leading zeros, “+”, bare dots, NaN or Infinity.
trailing-comma	Trailing comma before a closing bracket — not allowed in strict JSON.
comment	Comments are not allowed in strict JSON.
single-quote	JSON strings use double quotes.
unquoted-key	Unquoted key: JSON keys are double-quoted strings.
expected-colon	A colon is expected after the key.
expected-comma	A comma or closing bracket is expected — a comma between items may be missing.
expected-key	A double-quoted key is expected.
trailing-data	Extra data after the value — a JSON document holds one top-level value.
too-deep	Nesting is too deep (over 1,000 levels).

empty

Message: The input is empty.

unexpected-end

Message: Unexpected end of data: a closing bracket, quote or value is missing.

unexpected-char

Message: Unexpected character: a value was expected here (a double-quoted string, number, true, false, null, object or array).

unterminated-string

Message: Unterminated string: no matching quote before the end of the line.

bad-escape

Message: Invalid escape sequence. JSON allows \" \\ \/ \b \f \n \r \t and \uXXXX.

control-char

Message: Control character inside a string: write tabs and line breaks as \t and \n.

bad-number

Message: Invalid number: JSON has no leading zeros, “+”, bare dots, NaN or Infinity.

trailing-comma

Message: Trailing comma before a closing bracket — not allowed in strict JSON.

comment

Message: Comments are not allowed in strict JSON.

single-quote

Message: JSON strings use double quotes.

unquoted-key

Message: Unquoted key: JSON keys are double-quoted strings.

expected-colon

Message: A colon is expected after the key.

expected-comma

Message: A comma or closing bracket is expected — a comma between items may be missing.

expected-key

Message: A double-quoted key is expected.

trailing-data

Message: Extra data after the value — a JSON document holds one top-level value.

too-deep

Message: Nesting is too deep (over 1,000 levels).

JSON error messages (shown with line, column and a snippet)

Limitations

Relaxed JSON is not full JSON5: it accepts only comments, trailing commas, single-quoted strings and unquoted keys. Hex numbers, NaN and Infinity are still errors.
Integers above 2^53 lose precision (that is how JavaScript numbers work) — the tool warns about each one. Integer-like keys (“10”, “2”) come first in objects — that is JavaScript property order.
Duplicate keys: JSON keeps the last value with a warning; in YAML it is an error (the spec requires unique keys).
In CSV an empty cell and null look the same; empty arrays create no columns in tags[0] mode — choose “JSON in a cell” to keep them. Keys containing a dot become nesting when read back.
TypeScript types are inferred from the sample: values missing from the data are not in the type. YAML comments and source formatting are not preserved.
Input up to 10 MB; up to 1 MB of the result is shown (copy or download for all of it), highlighting up to 100 KB.

Privacy

Data is parsed in your browser, in a background thread of this page; neither input nor result is sent anywhere, and the page address does not change.
Input up to 200 KB and settings are kept in this browser only (localStorage) so the draft survives a reload; larger input lives only in the tab’s memory. “Reset all” deletes the data.
Analytics receives only the fact of a copy or download and the format pair (e.g. json → yaml) — never the content.
The result reaches us only if you send a request yourself and keep the “Attach the result” box ticked — the form shows exactly what will be sent. Files and images are never sent with a request.
The request summary holds only the formats, sizes, key and row counts, the error position and the number of warnings; the data itself, the output, key names and the filter path never go into it.