How to Extract All Keys from a JSON Object

Extracting all keys from a JSON object is one of the most common tasks when exploring unfamiliar API responses, building data pipelines, or documenting schemas. This guide covers four methods - from quick one-liners to full recursive implementations - so you can choose the right tool for the job.

Why Extract JSON Keys?

Before writing code to process a JSON response, you need to know what fields are available. Key extraction is especially useful when:

• Integrating a new third-party API for the first time
• Building field mappings for data transformations or ETL pipelines
• Documenting a JSON schema for your team
• Debugging why a parser cannot find a field you expect to be there

Method 1: JavaScript - Object.keys()

Object.keys() returns only the top-level keys of an object:

const json = {
  "name": "Alice",
  "age": 30,
  "address": { "city": "London", "zip": "EC1A 1BB" }
};

console.log(Object.keys(json));
// ["name", "age", "address"]

This misses nested keys like address.city. For flat JSON this is enough, but for anything nested you need a recursive approach.

Method 2: Recursive JavaScript

To get every key path - including nested objects and arrays - write a recursive function:

function getAllKeys(obj, prefix = '') {
    let keys = [];
    for (const key in obj) {
        if (!obj.hasOwnProperty(key)) continue;
        const fullKey = prefix ? `${prefix}.${key}` : key;
        keys.push(fullKey);
        const value = obj[key];
        if (Array.isArray(value)) {
            value.forEach((item, i) => {
                if (typeof item === 'object' && item !== null) {
                    keys = keys.concat(getAllKeys(item, `${fullKey}[${i}]`));
                }
            });
        } else if (typeof value === 'object' && value !== null) {
            keys = keys.concat(getAllKeys(value, fullKey));
        }
    }
    return keys;
}

const json = JSON.parse(jsonString);
console.log(getAllKeys(json));

Method 3: Python

Python's approach is equally straightforward using a recursive generator:

import json

def get_all_keys(obj, prefix=''):
    keys = []
    if isinstance(obj, dict):
        for k, v in obj.items():
            full_key = f"{prefix}.{k}" if prefix else k
            keys.append(full_key)
            keys.extend(get_all_keys(v, full_key))
    elif isinstance(obj, list):
        for i, v in enumerate(obj):
            keys.extend(get_all_keys(v, f"{prefix}[{i}]"))
    return keys

with open('data.json') as f:
    data = json.load(f)

print('\n'.join(get_all_keys(data)))

Method 4: JSON Keyper - No Code Required

If you just need to see the keys quickly without writing or running any code, JSON Keyper handles it instantly in your browser:

1. Paste your JSON into the left input box
2. Click Extract Keys
3. View every key path in the right output box
4. Click Copy to send them all to your clipboard

JSON Keyper handles nested objects and arrays automatically using the same dot notation and bracket notation as the code examples above - but with zero setup.

Which Method Should You Use?

Scenario	Best Approach
Quick one-off exploration	JSON Keyper
Automated pipeline or script	Python recursive function
Browser-side JavaScript processing	JS recursive function
Top-level keys only, flat JSON	Object.keys()