---
description: 'Perturbs a JSON string with random variations.'
sidebar_label: 'fuzzJSON'
sidebar_position: 75
slug: /sql-reference/table-functions/fuzzJSON
title: 'fuzzJSON'
---

# fuzzJSON Table Function

Perturbs a JSON string with random variations.

## Syntax {#syntax}

```sql
fuzzJSON({ named_collection [, option=value [,..]] | json_str[, random_seed] })
```

## Arguments {#arguments}

| Argument                           | Description                                                                                 |
|------------------------------------|---------------------------------------------------------------------------------------------|
| `named_collection`                 | A [NAMED COLLECTION](sql-reference/statements/create/named-collection.md).                  |
| `option=value`                     | Named collection optional parameters and their values.                                      |
| `json_str` (String)                | The source string representing structured data in JSON format.                              |
| `random_seed` (UInt64)             | Manual random seed for producing stable results.                                            |
| `reuse_output` (boolean)           | Reuse the output from a fuzzing process as input for the next fuzzer.                       |
| `malform_output` (boolean)         | Generate a string that cannot be parsed as a JSON object.                                   |
| `max_output_length` (UInt64)       | Maximum allowable length of the generated or perturbed JSON string.                         |
| `probability` (Float64)            | The probability to fuzz a JSON field (a key-value pair). Must be within [0, 1] range.       |
| `max_nesting_level` (UInt64)       | The maximum allowed depth of nested structures within the JSON data.                        |
| `max_array_size` (UInt64)          | The maximum allowed size of a JSON array.                                                   |
| `max_object_size` (UInt64)         | The maximum allowed number of fields on a single level of a JSON object.                    |
| `max_string_value_length` (UInt64) | The maximum length of a String value.                                                       |
| `min_key_length` (UInt64)          | The minimum key length. Should be at least 1.                                               |
| `max_key_length` (UInt64)          | The maximum key length. Should be greater or equal than the `min_key_length`, if specified. |

## Returned value {#returned_value}

A table object with a a single column containing perturbed JSON strings.

## Usage Example {#usage-example}

```sql
CREATE NAMED COLLECTION json_fuzzer AS json_str='{}';
SELECT * FROM fuzzJSON(json_fuzzer) LIMIT 3;
```

```text
{"52Xz2Zd4vKNcuP2":true}
{"UPbOhOQAdPKIg91":3405264103600403024}
{"X0QUWu8yT":[]}
```

```sql
SELECT * FROM fuzzJSON(json_fuzzer, json_str='{"name" : "value"}', random_seed=1234) LIMIT 3;
```

```text
{"key":"value", "mxPG0h1R5":"L-YQLv@9hcZbOIGrAn10%GA"}
{"BRE3":true}
{"key":"value", "SWzJdEJZ04nrpSfy":[{"3Q23y":[]}]}
```

```sql
SELECT * FROM fuzzJSON(json_fuzzer, json_str='{"students" : ["Alice", "Bob"]}', reuse_output=true) LIMIT 3;
```

```text
{"students":["Alice", "Bob"], "nwALnRMc4pyKD9Krv":[]}
{"students":["1rNY5ZNs0wU&82t_P", "Bob"], "wLNRGzwDiMKdw":[{}]}
{"xeEk":["1rNY5ZNs0wU&82t_P", "Bob"], "wLNRGzwDiMKdw":[{}, {}]}
```

```sql
SELECT * FROM fuzzJSON(json_fuzzer, json_str='{"students" : ["Alice", "Bob"]}', max_output_length=512) LIMIT 3;
```

```text
{"students":["Alice", "Bob"], "BREhhXj5":true}
{"NyEsSWzJdeJZ04s":["Alice", 5737924650575683711, 5346334167565345826], "BjVO2X9L":true}
{"NyEsSWzJdeJZ04s":["Alice", 5737924650575683711, 5346334167565345826], "BjVO2X9L":true, "k1SXzbSIz":[{}]}
```

```sql
SELECT * FROM fuzzJSON('{"id":1}', 1234) LIMIT 3;
```

```text
{"id":1, "mxPG0h1R5":"L-YQLv@9hcZbOIGrAn10%GA"}
{"BRjE":16137826149911306846}
{"XjKE":15076727133550123563}
```

```sql
SELECT * FROM fuzzJSON(json_nc, json_str='{"name" : "FuzzJSON"}', random_seed=1337, malform_output=true) LIMIT 3;
```

```text
U"name":"FuzzJSON*"SpByjZKtr2VAyHCO"falseh
{"name"keFuzzJSON, "g6vVO7TCIk":jTt^
{"DBhz":YFuzzJSON5}
```
