n8n intermediate: API calls, webhooks, expressions and error handling on one page

By Robert Breen · Published October 17, 2026 · From the free lesson n8n: Call Any API with the HTTP Request Node

A free one-page n8n intermediate cheat sheet: HTTP Request settings, GET vs POST, webhook URLs, expressions, items, AI approval and error handling.

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Free, no sign-up and no email needed. It prints on one letter-size page; the whole sheet is below.

▶StepthroughFree printable cheat sheet · learn.ynteractive.com

n8n intermediate: API calls, webhooks, expressions and error handling on one page

The settings that turn a first n8n workflow into one the business runs on, from the free n8n Intermediate course.

HTTP Request: call any API

Method: GET reads and changes nothing. POST sends data to create something.
URL: The address from the app's API docs, like https://jsonplaceholder.typicode.com/users.
Send Query Parameters: Narrow a GET: Name username, Value Samantha adds ?username=Samantha.
Send Body: For POST: JSON, Using Fields Below, one field per value.
Authentication: A saved credential. Never paste a key into the URL or body.

Data and expressions

Item: One record. A node runs once per item.
Expression: {{ $json.email }} = this item's email. Drag a field from INPUT onto a box to make one.
Output views: Schema, Table and JSON show the same data three ways.

Triggers that run without you

Schedule Trigger: At a set time, in the workflow's time zone.
Webhook Test URL: Listens only while you click Listen for test event.
Webhook Production URL: Listens all the time after Publish. This one goes in the live form.

Safe AI and error handling

Save AI replies as Gmail drafts; a person sends them.
An error workflow (Error Trigger + email) tells you when any workflow fails.
Retry On Fail for flaky steps; Executions to retry a failed run.
Green checks mean a node ran. Check the real result: the sheet, the inbox, the CRM.

Remember: Test with Execute step on real-looking data, check where the result lands, then Publish. Every change after that needs another Publish.

Practice it free: n8n: Call Any API with the HTTP Request Node at learn.ynteractive.com/modules/n8n-http-request-api. This sheet: learn.ynteractive.com/content/cheat-sheets/n8n-intermediate. Harbor Lane Marketing is a made-up business from the lesson. By Robert Breen, October 17, 2026.

Practice it in the free lesson

n8n: Call Any API with the HTTP Request Node. Connect n8n to any app with an API: GET a CRM's client list, filter it with a query parameter, then POST a note back using an expression. Free practice API, no key needed. You do every step yourself in a practice copy of n8n, it checks your work as you go, and “Do it for me” finishes any step you get stuck on. Free, and nothing touches your real accounts.

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Or read the full step-by-step guide

Lessons on this sheet

n8n HTTP Request node with Method GET and the URL https://jsonplaceholder.typicode.com/users, and an OUTPUT table of 10 items with id, name and username

n8n: Call Any API with the HTTP Request Node

Connect n8n to any app with an API: GET a CRM's client list, filter it with a query parameter, then POST a note back using an expression. Free practice API, no key…

Free · Live ~9 min Intermediate

◷n8n: Read, Add and Update Google Sheets Rows with an AI Step

Learn n8n's three core Google Sheets moves on a made-up request list: read the rows, add a new one without duplicates, then let an AI step write a description and…

Free · Live ~12 min Intermediate

n8n Schedule Trigger settings with the Trigger at Hour dropdown open and 5pm being picked

Get Your Daily Revenue Total by Email, Automatically, using n8n

Stop spending 20 minutes every evening adding up the day by hand. In n8n, a Schedule Trigger runs at 5pm, Google Sheets pulls today's jobs, Summarize totals the revenue…

Free · Live ~9 min Intermediate

n8n On form submission trigger with a Request a free quote form title and name field

Webhooks and Forms in n8n: Capture Data from Anywhere

Stop losing quote requests between inboxes. Build a form n8n hosts for you, catch entries from your own website with a webhook, and save every request to one Google…

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n8n AI Email Responder: Draft Gmail Replies Automatically

Build an n8n agent that watches your Gmail, reads each new customer email, and writes a reply as a draft in the same thread, ready for you to check and send.

Free · Live ~12 min Intermediate

n8n Error Trigger node in an error alerts workflow, which has no parameters to set

Get Alerted When an n8n Automation Fails, and Let It Retry by Itself

A silent failure means a stale price sheet and wrong quotes. In n8n, build an error workflow that emails you, make a flaky step retry by itself, send its failures down…

Free · Live ~10 min Intermediate

Plain-English definitions, each with an example from a free lesson.

HTTP Request node Query parameter Request body (payload)Expression Item (n8n)Credential Test URL vs production URL Error handling

The full AI glossary

AI agent system message prompt: Draft the system message for an n8n AI Agent: who it is, what it knows, its rules and how it writes, including a rule never to…
Daily priorities plan prompt: Paste your to-do list and fixed times and get a realistic plan for today: top three, time blocks, a buffer, and what to move to…
"Do you service my area?" reply prompt: Answer "do you cover my town?" from your real service area list: a clear yes with how to book, a kind no, or a request for the…
FAQ from customer emails prompt: Turn a batch of customer emails into an FAQ: the questions people really ask, in their words, answered only from your facts…

All free prompt templates