n8n-nodes-input-validation

Custom n8n community node for validating incoming API and webhook data — parameters, body fields, and headers — and routing the result to Valid or Invalid outputs.

When you use n8n as an API gateway, every endpoint needs to check that required fields exist and match the expected format. Today that usually means chaining Webhook → IF → SET → Respond to Webhook just to return a 400 with a readable error. This package replaces that pattern with a single node.

What does it do?

The Input Validation node reads fields from the incoming item (using dot-notation paths like body.email or query.page), evaluates your rules, and:

• Valid — passes the original input through unchanged (continue your workflow)
• Invalid — outputs a ready-made error object for Respond to Webhook (status code, plain-text error, and structured errors array)

No credentials required. Works with any trigger that outputs JSON (typically Webhook).

Before vs After

Without this node:

Webhook → IF (field checks) → SET (build error JSON) → Respond to Webhook
         → IF (else branch)  → your business logic

With this node:

Webhook → Input Validation ─ Valid   → your business logic → Respond 200
                          └ Invalid → Respond to Webhook ({{ $json }})

Node in this Package

| Node | Type | Description | |------|------|-------------| | Input Validation | Transform | Validate fields with rule groups; route to Valid or Invalid |

Installation

Community Nodes (Recommended)

1. Go to Settings → Community Nodes in your n8n instance
2. Click Install a community node
3. Enter n8n-nodes-input-validation
4. Click Install and restart n8n if prompted

Manual Installation

cd ~/.n8n/custom   # or your N8N_CUSTOM_EXTENSIONS path
npm install n8n-nodes-input-validation
# Restart n8n

Input Validation Node

Configuration

| Setting | Description | |---------|-------------| | Combine Groups | AND = every group must pass · OR = at least one group must pass | | Rule Groups | One or more groups of conditions (see below) | | Combine Conditions (per group) | AND = all conditions in the group · OR = at least one condition | | Field | Dot-notation path on the incoming JSON, e.g. body.email, query.page, headers.x-api-key | | Operation | See Operators | | Value | Comparison value (not used for empty/boolean-only operations) | | Default Value | When the field is missing: skip this condition, and add the default to the Valid output JSON | | Error Message | Optional custom text when this condition fails |

Options

| Option | Default | Description | |--------|---------|-------------| | Ignore Case | true | Case-insensitive string comparisons | | Error Status Code | 400 | HTTP code in the Invalid output (statusCode) | | Include Original Input | false | Adds original with the full input JSON on Invalid | | Error Message | Validation failed | Summary text in the Invalid output (message) |

How it works

1. A request hits your workflow (e.g. via Webhook)
2. The node reads each configured Field from the item JSON
3. Conditions are evaluated inside each Rule Group, then groups are combined with Combine Groups
4. All rules pass → item goes to the Valid output (unchanged)
5. Any rule fails → item goes to the Invalid output with a structured error payload

Operators

| Operation | Value | Description | |-----------|-------|-------------| | Is Empty | — | null, undefined, "", or empty array | | Is Not Empty | — | Field must have a value | | Contains | Yes | String contains the value | | Does Not Contain | Yes | String does not contain the value | | Equals | Yes | String equality (respects Ignore Case) | | Does Not Equal | Yes | String inequality | | Greater Than | Yes | Numeric comparison (body.age > 18) | | Less Than | Yes | Numeric comparison | | Is True | — | Value must be true (boolean, or true / 1 as string) | | Is False | — | Value must be false (boolean, or false / 0 as string) | | Is Boolean | — | Value must be a valid boolean (true or false) |

Accepts native booleans and common API string forms: true, false, 1, 0 (case-insensitive).

Rule groups example

Validate that either (email AND age) or (premium OR enterprise plan):

| Combine Groups | OR | |----------------|--------| | Group 1 — Combine Conditions: AND | body.email · Is Not Empty | | | body.age · Greater Than · 18 | | Group 2 — Combine Conditions: OR | query.type · Equals · premium | | | query.type · Equals · enterprise |

Logic: (email ∧ age>18) ∨ (type=premium ∨ type=enterprise)

Invalid Output

When validation fails, the Invalid branch receives:

{
  "valid": false,
  "statusCode": 400,
  "message": "Validation failed",
  "error": "body.email must not be empty; body.age must be greater than 18",
  "errors": [
    {
      "field": "body.email",
      "operation": "isNotEmpty",
      "message": "body.email must not be empty",
      "received": null
    },
    {
      "field": "body.age",
      "operation": "greaterThan",
      "message": "body.age must be greater than 18",
      "received": "12"
    }
  ]
}

| Field | Use | |-------|-----| | statusCode | Set Respond to Webhook → Response Code to {{ $json.statusCode }} | | error | Plain-text body — all failures joined with ; | | errors | Full list for logging or JSON API responses | | message | Short summary line | | original | Present only if Include Original Input is enabled |

Examples

Example: Missing field with default (skip + inject)

| Field | Operation | Default Value | |-------|-----------|---------------| | Test | Is Empty | false |

Input: { "ClientName": "Moses" } — no Test field.

• The Is Empty condition is skipped (field does not exist)
• Valid output: { "ClientName": "Moses", "Test": false }

If the client sends Test, the condition runs normally (Is Empty must pass).

Example: POST API with required body fields

Workflow:

Webhook (POST /api/orders)
  → Input Validation
      Valid   → Create Order → Respond to Webhook (200)
      Invalid → Respond to Webhook
                  Response Code: {{ $json.statusCode }}
                  Response Body: {{ $json }}

Rules (single group, AND):

| Field | Operation | Value | |-------|-----------|-------| | body.customer_id | Is Not Empty | | | body.amount | Greater Than | 0 | | body.currency | Equals | USD |

Invalid response (what the client sees if body.amount is missing):

{
  "valid": false,
  "statusCode": 400,
  "message": "Validation failed",
  "error": "body.amount must not be empty",
  "errors": [ ... ]
}

Example: Simple text error response

Connect Invalid → Respond to Webhook:

• Response Code: {{ $json.statusCode }}
• Response Body: {{ $json.error }}

Client receives: body.email must not be empty; body.age must be greater than 18

Example: calling the webhook

curl -X POST https://your-n8n.com/webhook/orders \
  -H "Content-Type: application/json" \
  -d '{"customer_id": "c_1", "amount": 99, "currency": "USD"}'

License

MIT