Compare API JSON Responses

Diff old and new API responses to catch contract drift, missing fields, changed values, and unexpected nested objects.

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→ Compare these JSON inputs and return a report of changed, added, and removed fi...

Output✓

{
  "plan": "pro",
  "features": {
    "aiDraft": true,
    "history": true,
    "apiAccess": true
  },
  "limits": {
    "documents": 100
  }
}

Output✓

1{
2  "changed": [
3    {
4      "kind": "changed",
5      "path": "plan",
6      "before": "starter",
7      "after": "pro"
8    },
9    {
10      "kind": "changed",
11      "path": "features.aiDraft",
12      "before": false,
13      "after": true
14    },
15    {
16      "kind": "changed",
17      "path": "limits.documents",
18      "before": 10,
19      "after": 100
20    }
21  ],
22  "added": [
23    {
24      "kind": "added",
25      "path": "features.apiAccess",
26      "value": true
27    }
28  ],
29  "removed": [
30    {
31      "kind": "removed",
32      "path": "features.legacyExport",
33      "value": true
34    }
35  ]
36}

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.

Read integration guide

Works with:

REST and GraphQL responses
Webhook payloads
Sandbox vs production
API contract QA

Example: input → output

Inputs / Output

Output

Compare API JSON responses

Compare API JSON responses when an endpoint changes between releases, environments, accounts, vendors, or repeated pulls. API drift is rarely obvious at first glance. A response may still be valid JSON while silently removing a field, changing a type, adding a nested object, or returning a different enum value.

This page uses the same engine as the JSON diff tool, but the workflow is written for REST responses, GraphQL results, webhook bodies, SDK output, and sandbox-versus-production checks.

Why API response comparison matters

Applications usually depend on paths and types, not on how a response is formatted. If customer.plan changes from "free" to "pro", downstream billing code might behave differently. If items.0.price changes from a number to a string, analytics or validation can fail. If a webhook removes event.type, a handler may route the event incorrectly.

A structured response diff turns those changes into a readable checklist. It separates added fields from removed fields and changed values, which helps engineering, QA, support, and integration teams discuss the impact without reading a full payload.

API diff workflow

Paste the known-good response, previous version, or production sample into the baseline side. Paste the newer response, staging response, or vendor sample into the comparison side. Run the diff, then inspect changed paths for contract drift.

Before comparing, validate both payloads with JSON Validator. If vendor responses include unstable fields such as timestamps, request IDs, or signatures, extract only the stable paths with Extract Fields from JSON. If the API returns inconsistent naming, normalize records with Normalize JSON first.

Common API response checks

Use API response comparison before releasing a backend change, upgrading a vendor SDK, modifying an OpenAPI contract, replacing a webhook provider, or debugging a customer-only production issue. It is also useful for checking whether staging and production return the same shape for the same endpoint.

For paginated APIs, compare representative pages or combine pages before diffing. For deeply nested responses, Flatten JSON can make paths easier to review. For spreadsheet handoff, convert selected comparison data with JSON to CSV.

Avoid noisy API diffs

Some API fields are expected to change every run, such as createdAt, updatedAt, requestId, traceId, and signatures. Remove or ignore those fields before comparison when they are not part of the contract you are reviewing. The cleanest report compares stable business fields, required contract fields, and values that downstream systems actually consume.

JSON Diff Tool - canonical structured diff workflow for added, removed, and changed fields.
JSON compare tool online - compare objects, arrays, files, and API payloads by path.
JSON difference checker - changed-field reporting for debugging payload drift.
Compare JSON files online - file-focused comparison for fixtures, configs, and exports.
JSON diff online - browser-based no-upload JSON comparison.
API JSON diff - compare endpoint, webhook, and SDK response changes.
Compare JSON objects - object-level field comparison.
JSON file diff - saved-file and fixture diff workflow.
Find JSON changes - added, removed, and modified field detection.

JSON Validator - validate API payloads before comparing them.
JSON Formatter - clean and format API payloads before diffing.
Clean JSON - remove formatting and empty-field noise before API diffing.
API response formatter - clean vendor, REST, GraphQL, and webhook responses.
Extract Fields from JSON - compare only stable contract fields.
Normalize JSON - align inconsistent API response shapes.
Flatten JSON - review nested response paths more easily.

Related tools

Related comparisons

JSON Diff / Change Report

v1.0.0

Compare

objectarray

Description

JSON Diff / Change Report

Compare two JSON inputs and output a structured report or focused diff subset. Accepts a primary input (the new JSON) and secondary input (the old JSON), then shows what changed, was added, or was removed between them.

How It Works

This utility requires two inputs — primary (the "new" version) and secondary (the "old" version). It performs a deep comparison and outputs results based on the selected mode.

Diff Modes

Report

Return a structured report with changed, added, and removed arrays. Entries include dot paths, kind, and either before/after values or the added/removed value.

Changed Only

Return the subset of the new JSON that differs from the old JSON. Modified and added fields are included; removed fields are excluded because they do not exist in the new JSON.

Added Only

Show only fields that exist in the primary input but not in the secondary. Useful for detecting new additions.

Removed Only

Show only fields that exist in the secondary input but not in the primary. Useful for detecting deletions.

Full Annotated

Show all fields with _diff_ markers indicating their status: "unchanged", "changed", "added", or "removed". Provides a complete picture of all differences.

Configuration

Field	Type	Default	Description
Diff Mode	enum	`report`	`report`, `changed-only`, `added-only`, `removed-only`, or `full-annotated`

Use Cases

Version Comparison

Config changes: Compare two versions of a configuration file to see what changed
API responses: Diff API responses before and after a deployment
Schema evolution: Identify added or removed fields between schema versions

Data Validation

Migration verification: Compare source and target data after migration
Sync detection: Find out-of-sync records between two data sources
Audit trail: Track exactly which fields were modified in an update

Debugging

State inspection: Compare application state before and after an action
Response diffing: Compare expected vs. actual API responses
Regression detection: Identify unexpected changes in output data

Configuration

Name	Type	Default	Description
Diff Mode	`enum`	`report`	report: return changed, added, and removed entries with paths. changed-only: show the new JSON subset with modified and added values. added-only: show only new keys. removed-only: show only deleted keys. full-annotated: show all with _diff markers. `report` `changed-only` `added-only` `removed-only` `full-annotated`

Examples

AI Prompt

Compare these JSON inputs and return a report of changed, added, and removed fields.

Output✓

{
  "plan": "pro",
  "features": {
    "aiDraft": true,
    "history": true,
    "apiAccess": true
  },
  "limits": {
    "documents": 100
  }
}

Output✓

1{
2  "changed": [
3    {
4      "kind": "changed",
5      "path": "plan",
6      "before": "starter",
7      "after": "pro"
8    },
9    {
10      "kind": "changed",
11      "path": "features.aiDraft",
12      "before": false,
13      "after": true
14    },
15    {
16      "kind": "changed",
17      "path": "limits.documents",
18      "before": 10,
19      "after": 100
20    }
21  ],
22  "added": [
23    {
24      "kind": "added",
25      "path": "features.apiAccess",
26      "value": true
27    }
28  ],
29  "removed": [
30    {
31      "kind": "removed",
32      "path": "features.legacyExport",
33      "value": true
34    }
35  ]
36}

Config

Diff Mode

report

API Usage

POST /api/v1/utilities/compare.json-diff

Example:

curl -X POST https://your-domain.com/api/v1/utilities/compare.json-diff \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"inputs":{"primary":{"plan":"pro","features":{"aiDraft":true,"history":true,"apiAccess":true},"limits":{"documents":100}},"secondary":{"plan":"starter","features":{"aiDraft":false,"history":true,"legacyExport":true},"limits":{"documents":10}}},"config":{"mode":"report"}}'

Response

1{
2  "changed": [
3    {
4      "kind": "changed",
5      "path": "plan",
6      "before": "starter",
7      "after": "pro"
8    },
9    {
10      "kind": "changed",
11      "path": "features.aiDraft",
12      "before": false,
13      "after": true
14    },
15    {
16      "kind": "changed",
17      "path": "limits.documents",
18      "before": 10,
19      "after": 100
20    }
21  ],
22  "added": [
23    {
24      "kind": "added",
25      "path": "features.apiAccess",
26      "value": true
27    }
28  ],
29  "removed": [
30    {
31      "kind": "removed",
32      "path": "features.legacyExport",
33      "value": true
34    }
35  ]
36}

Love the result?

Example: input → output

Compare API JSON responses

Why API response comparison matters

API diff workflow

Common API response checks

Avoid noisy API diffs

Related conversions

Related tools

Related tools

Related comparisons

Read more on the blog

JSON Diff / Change Report

Description

JSON Diff / Change Report

How It Works

Diff Modes

Report

Changed Only

Added Only

Removed Only

Full Annotated

Configuration

Use Cases

Version Comparison

Data Validation

Debugging

Configuration

Examples

API Usage

Related Tools

JSON Validator

JSON Formatter

JSON to CSV

Clean Values

Flatten / Nest