JSON to YAML
Convert JSON to clean, correctly quoted YAML in one step.
JSON Unflattener
Rebuild nested JSON from flat dot-notation or bracket-notation keys.
Bracket notation is understood automatically, whatever this is set to.
Quick Tool Overview
The JSON Unflattener rebuilds nested JSON from a flat object of path keys. Numeric path segments become array indexes and everything else becomes an object key, and it reads dot notation, bracket notation or a mixture of the two.
- What it does
- Expands flat path keys back into nested JSON
- You give it
- A single-level object keyed by paths
- You get back
- A properly nested document with real arrays
- Best for
- Turning env files, form posts and spreadsheet rows into API payloads
About the JSON Unflattener
Unflattening is the inverse of flattening: a single-level object whose keys are paths becomes a properly nested document. The key "user.address.city" creates the objects it names, and a numeric segment such as "items.0.sku" creates an array rather than an object.
It is the step that turns machine-friendly storage back into something an API will accept. Flat keys are how environment files, spreadsheet columns, form posts and key-value stores hold structured data, and every one of those eventually has to be sent somewhere that expects real nesting. The parser accepts dot notation, bracket notation and a document that mixes the two, which hand-edited config files frequently do.
Key features of the JSON Unflattener
Arrays are rebuilt, not faked
A numeric path segment produces a real array, so items.0.sku comes back as a list of objects rather than an object with "0" as a key.
Reads both notations
Dot and bracket keys are both understood, including a document that mixes them — which hand-edited config files routinely do.
A configurable separator
Match whatever character your keys were joined with, so the round trip through the Flattener is lossless.
Deep nesting is fine
Paths of any length rebuild correctly; the structure is created level by level as each key is read.
Formatted output
The rebuilt document is indented and ready to send, not returned as one line.
How to use the JSON Unflattener
-
1
Paste the flat JSON
A single-level object whose keys are paths, in dot or bracket notation.
-
2
Set the separator
Leave it as a dot, or change it if your keys are joined with underscores or slashes.
-
3
Check the nesting
Numeric segments become array indexes; everything else becomes an object key.
-
4
Copy the result
The nested document is formatted and ready to send.
Frequently asked questions
By the path segment. A segment made only of digits creates an array index; anything else creates an object key. So items.0.sku produces an array of objects.
Yes, and it can read a document that mixes both forms. user[address].city and user.address.city produce the same result.
Change the separator to a character your keys do not use — an underscore, a slash or a pipe — and flatten with the same setting so the round trip stays exact.
Missing indexes are dropped rather than filled with nulls, so 0 and 2 produce a two-item array. Provide every index when the positions matter.
Reviews of the JSON Unflattener
What people who use the JSON Unflattener think of it. Reviews come from visitors and are posted as written.
No ratings yet
Yours would be the first.
- 5 0 reviews rated 5 stars
- 4 0 reviews rated 4 stars
- 3 0 reviews rated 3 stars
- 2 0 reviews rated 2 stars
- 1 0 reviews rated 1 star
0 reviews
Newest first
No reviews yet
Be the first to rate the JSON Unflattener. It takes half a minute and no account.
Write the first reviewMore developer tools
JWT Generator
Build and sign a JWT with HS256, HS384 or HS512 for testing.
JSON to Rust Struct
Generate serde-ready Rust structs from a sample JSON document.
Port Number Lookup
Find what runs on a port, with a note on whether it should be exposed.
JSON to TOML
Turn a JSON object into a TOML document with proper tables and arrays of tables.
XPath Tester
Run XPath expressions against your own XML and see every node that matches.
JSON to C# Class
Generate C# classes with System.Text.Json attributes from a JSON sample.
JSON Sorter
Sort JSON object keys alphabetically at every level, or sort arrays by a field.