Flatten JSON Online Free
Paste nested JSON and flatten it in your browser for free. No signup, no upload step, and no local script just to inspect a payload.
Paste your JSON → Get results instantly (no signup)
→ Flatten or nest keys in this JSON structure and flatten nested object.
1{2 "user.name": "Alice",3 "user.address.city": "NYC",4 "user.address.zip": "10001"5}Love the result?
Use this exact pipeline in your app, backend, or LLM workflow.
No setup needed. Works with curl, Node, Python.
Uses example data. For edited input, copy from the playground.
Works with:
- No-signup JSON flattening
- Browser-local payload checks
- One-off API debugging
- CSV-ready output
Example: input → output
Flatten JSON online free
Sometimes you do not need a package, script, account, or upload flow. You just need to paste a nested payload, flatten it, and copy the result. This free online JSON flattener is for one-off API debugging, spreadsheet prep, test fixtures, and quick path inspection.
It uses the same engine as the JSON flattener, but this page focuses on no-signup, browser-based usage.
What you get
- Flatten nested JSON objects into dotted path keys.
- Flatten arrays of records into row-like objects.
- Preserve JSON value types such as numbers, booleans, strings, arrays, and nulls.
- Choose delimiters such as
.,_, or/. - Reverse flat keys back into nested JSON with Unflatten JSON.
Online JSON flattener example
Input:
{
"account": {
"id": "acct_1",
"owner": {
"email": "ada@example.com"
}
}
}Output:
{
"account.id": "acct_1",
"account.owner.email": "ada@example.com"
}That is enough for many practical tasks: paste into a ticket, compare with another payload, or convert to CSV.
Best way to flatten JSON online in 2026
The best no-signup workflow is simple: validate the JSON first if it came from a copied snippet, flatten it with the delimiter your destination supports, then export or diff the result. If the payload is headed to a spreadsheet, use Flatten JSON for CSV. If it came from an endpoint, use Flatten API Response JSON.
Avoid tools that silently stringify nested values or change numbers into strings unless that is exactly what your destination needs.
Browser-based vs upload-based tools
Browser-based flattening is best for quick, sensitive, or internal samples because the workflow stays local to the page. Upload-based tools may be fine for public demo data, but they are unnecessary for most JSON flattening tasks.
For very large files, browser memory still matters. Use Flatten Large JSON Files for the large-file workflow and limits.
Related flatten JSON tools
- JSON flattener - the main flatten and nest tool.
- Flatten JSON with a delimiter - choose dot, slash, or underscore path keys.
- Flatten JSON Array - handle arrays of records.
- Flatten JSON in JavaScript - compare online output with helper code.
Frequently asked questions
Is this JSON flattener free?+−
Yes. The online flattening workflow is free to use for one-off nested JSON, arrays, API responses, and CSV preparation.
Do I need to upload my JSON?+−
No upload step is required for the browser-based workflow. Paste JSON into the tool, flatten it, and copy the result.
What is the best way to flatten JSON online?+−
Validate the JSON if needed, choose the delimiter your destination supports, flatten nested objects, then export, diff, or unflatten based on the workflow.
Related tools
- Rename KeysRename known keys or convert key casing without changing the underlying values
- Find & ReplaceFind and replace matching keys or values across JSON using broad search patterns
- FilterFilter rows, items, keys, or values by explicit conditions and keep only the matches you want
- Pick FieldsKeep only a known allowlist of fields and remove everything else
- RestructureFlexibly restructure collections by grouping, unwinding, transposing, or rearranging nested data
Read more on the blog
Advanced usage (optional)
Flatten / Nest
v1.0.0Description
Flatten / Nest
Convert between nested and flat object structures. Flatten deep objects into single-level key-value pairs, or nest flat keys back into hierarchical objects. Supports multiple key formats: delimiter-separated, camelCase, snake_case, PascalCase, and kebab-case.
Modes
Flatten
Convert nested objects into flat keys. Each nested path becomes part of the key name.
{ "user": { "name": "Alice" } } → { "user.name": "Alice" }Nest
Convert flat keys back into nested objects by splitting on the delimiter or case boundaries.
{ "user.name": "Alice" } → { "user": { "name": "Alice" } }Key Formats
Delimiter (default)
Join/split key segments with a character (default: .).
- Flatten:
user+name→user.name - Nest:
user.name→user/name
camelCase
Join/split on uppercase letter boundaries.
- Flatten:
user+address+city→userAddressCity - Nest:
userAddressCity→user/address/city
snake_case
Join/split on underscores.
- Flatten:
user+address+city→user_address_city - Nest:
user_address_city→user/address/city
PascalCase
Same as camelCase but with uppercase first letter.
- Flatten:
user+name→UserName
kebab-case
Join/split on hyphens.
- Flatten:
user+name→user-name
Configuration
| Field | Type | Default | Description |
|---|---|---|---|
| Mode | enum | flatten | flatten or nest |
| Key Format | enum | delimiter | delimiter, camelCase, snake_case, PascalCase, or kebab-case |
| Delimiter | string | . | Character(s) used to join/split key segments (only for delimiter format) |
| Max Depth | number | 0 | Maximum nesting depth to flatten (0 = unlimited) |
| Target Paths | path-picker | [] | Scope operation to specific paths only (empty = apply everywhere) |
Use Cases
API Integration
- Flatten for forms: Convert nested API responses to flat form field names
- Nest for APIs: Convert flat form data back to nested API request bodies
- Format conversion: Transform between dot-notation and camelCase conventions
Database Operations
- MongoDB flattening: Flatten nested documents for tabular export
- SQL mapping: Convert hierarchical JSON to flat column names for SQL insertion
- Schema migration: Convert between naming conventions (snake_case ↔ camelCase)
Configuration Management
- Environment variables: Flatten config objects to dot-notation for
.envfiles - Depth limiting: Flatten only the first level while preserving deep structures
Configuration
| Name | Type | Default | Description |
|---|---|---|---|
| Mode | enum | flatten | flatten: convert nested objects to flat keys. nest: convert flat keys back to nested objects. flatten nest |
| Key Format | enum | delimiter | delimiter: use a character to join/split. Others: camelCase, snake_case, PascalCase, kebab-case. delimiter camelCase snake_case PascalCase kebab-case |
| Delimiter | string | . | Character(s) used to join/split key segments (default is dot) |
| Max Depth | number | 0 | Maximum nesting depth to flatten (0 = unlimited) |
| Target Paths | path-picker | [] | Scope operation to specific paths only (empty = apply everywhere) |
Examples
Flatten or nest keys in this JSON structure and flatten nested object.1{2 "user.name": "Alice",3 "user.address.city": "NYC",4 "user.address.zip": "10001"5}API Usage
curl -X POST https://your-domain.com/api/v1/utilities/structure.flatten-nest \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{"inputs":{"primary":{"user":{"name":"Alice","address":{"city":"NYC","zip":"10001"}}}},"config":{"mode":"flatten","delimiter":".","maxDepth":0,"targetPaths":[]}}'1{2 "user.name": "Alice",3 "user.address.city": "NYC",4 "user.address.zip": "10001"5}