n8n Expression Syntax

Expert guide for writing correct n8n expressions in workflows.

Execution and data scope

EXAMPLES.md and COMMON_MISTAKES.md referenced below/in the guide are not bundled. $json in expression parameters represents the current input item, not a completed current node output; inspect actual execution data and item linking before referencing another node. Code-node APIs differ between per-item and all-items modes. Use credentials for secrets: the guide's $env examples can expose values and may be disabled. Avoid putting secrets/personal webhook data into messages or logs. Encode URL path/query components, guard missing arrays/objects and validate untrusted values before downstream actions. Test expressions with synthetic input; preview success is not authorization to send Slack/email messages.

Detailed Guide

Read the detailed guide before executing this skill. It retains the complete procedure and reference material. Treat its safety, prerequisites, and validation requirements as mandatory. For focused work, load the relevant sections; for end-to-end work, read the guide completely.

When to Use

• You need to write or debug n8n expressions using {{ ... }} syntax.
• The task involves $json, $node, webhook payloads, or expression-related workflow errors.
• You want syntax-correct dynamic values inside n8n nodes and parameters.