n8n-expression-syntax

# n8n Expression Syntax Expert guide for writing correct n8n expressions in workflows. --- ## Expression Format All dynamic content in n8n uses **double curly braces**: ``` {{expression}} ``` **Examples**: ``` ✅ {{$json.email}} ✅ {{$json.body.name}} ✅ {{$node["HTTP Request"].json.data}} ❌ $json.email (no braces - treated as literal text) ❌ {$json.email} (single braces - invalid) ``` --- ## Core Variables ### $json - Current Node Output Access data from the current node: ```javascript {{$json.fieldName}} {{$json['field with spaces']}} {{$json.nested.property}} {{$json.items[0].name}} ``` ### $node - Reference Other Nodes Access data from any previous node: ```javascript {{$node["Node Name"].json.fieldName}} {{$node["HTTP Request"].json.data}} {{$node["Webhook"].json.body.email}} ``` **Important**: - Node names **must** be in quotes - Node names are **case-sensitive** - Must match exact node name from workflow ### $now - Current Timestamp Access current date/time: ```javascript {{$now}} {{$now.toFormat('yyyy-MM-dd')}} {{$now.toFormat('HH:mm:ss')}} {{$now.plus({days: 7})}} ``` ### $env - Environment Variables Access environment variables: ```javascript {{$env.API_KEY}} {{$env.DATABASE_URL}} ``` **Warning**: Some n8n instances have `N8N_BLOCK_ENV_ACCESS_IN_NODE` enabled, which blocks `$env` access entirely. If `$env` returns errors, use alternative approaches: - Store values in credentials instead - Use a Set node with manually entered values - Pass values through webhook query parameters --- ## 🚨 CRITICAL: Webhook Data Structure **Most Common Mistake**: Webhook data is **NOT** at the root! ### Webhook Node Output Structure ```javascript { "headers": {...}, "params": {...}, "query": {...}, "body": { // ⚠️ USER DATA IS HERE! "name": "John", "email": "john@example.com", "message": "Hello" } } ``` ### Correct Webhook Data Access ```javascript ❌ WRONG: {{$json.name}} ❌ WRONG: {{$json.email}} ✅ CORRECT: {{$json.body.name}} ✅ CORRECT: {{$json.body.email}} ✅ CORRECT: {{$json.body.message}} ``` **Why**: Webhook node wraps incoming data under `.body` property to preserve headers, params, and query parameters. --- ## Common Patterns ### Access Nested Fields ```javascript // Simple nesting {{$json.user.email}} // Array access {{$json.data[0].name}} {{$json.items[0].id}} // Bracket notation for spaces {{$json['field name']}} {{$json['user data']['first name']}} ``` ### Reference Other Nodes ```javascript // Node without spaces {{$node["Set"].json.value}} // Node with spaces (common!) {{$node["HTTP Request"].json.data}} {{$node["Respond to Webhook"].json.message}} // Webhook node {{$node["Webhook"].json.body.email}} ``` ### Combine Variables ```javascript // Concatenation (automatic) Hello {{$json.body.name}}! // In URLs https://api.example.com/users/{{$json.body.user_id}} // In object properties { "name": "={{$json.body.name}}", "email": "={{$json.body.email}}" } ``` --- ## When