Event Ticketing Backend: Auto QR Tickets with Google Sheets & Gmail

Ticketing Backend automates registration, QR-ticket generation, email delivery, and check-in validation using Google Sheets, Gmail, and a webhook scanner — reducing manual ticket prep from ~3 hours to under 5 minutes for 200 attendees.

Why Use This Workflow?

Time Savings:** Automates ticket generation & delivery. reduces manual processing for 200 attendees from ~3 hours to <5 minutes. Cost Reduction:** Removes dependency on paid ticketing platforms for basic events — save up to $150–$300/month for small organizations. Error Prevention:** Single-source truth in Google Sheets with QR-based check-in reduces double-checkin and human errors by >90%. Scalability:** Runs on a schedule and webhooks; scales from dozens to thousands of tickets (watch API/email quotas).

Ideal For

Event Organizers / Community Managers:** Sell & distribute tickets for meetups, runs, and local events with immediate QR delivery. Operations / Venue Staff:** Fast, reliable check-in via mobile scanner POSTing to webhook for instant validation. Small Agencies & SaaS Teams:** Lightweight, low-cost ticketing backend that integrates with existing Google accounts.

How It Works

Trigger (Registration): POST /v1/register receives registration payload (nama, email, no_hp, jumlah_tiket, total_price, payment_method). Data Collection (Registration): Validate input → check existing participant in Register sheet → append registration. Processing (Ticket Generation): Scheduled job (START runs every minute) finds rows with Payment Status = PAID and Email Sent = NO. Intelligence Layer: For each ticket: generate unique Ticket ID (TL-YYYYMMDD-XXXX-N-HASH), build QR payload JSON, create QR image via qrserver API, and build HTML email with embedded base64 QR. Output & Delivery: Send ticket email(s) via Gmail; write one Tickets row per generated ticket and mark Email Sent = YES in Register. Storage & Logging: All participant & ticket records persisted to Google Sheets; check-in events update row (Checked In = YES and Checkin TIme).

Core Endpoints

Registration webhook: POST /v1/register Scanner webhook (check-in): POST /v1/scanner

Event Metadata

Event:** TABRAK_LARI Event date:** 15 November 2025 Event location:** GOR Pontianak

Setup Guide

Prerequisites

| Requirement | Type | Purpose | |-------------|------|---------| | n8n instance(https://n8n.partnerlinks.io/khmuhtadin)) | Essential | Host the workflow and webhooks | | Google account (Sheets + Gmail) | Essential | Store tickets & send emails | | Google Sheet | Essential | Register & Tickets data store | | Public webhook URL / reverse proxy | Essential | Expose /v1/register & /v1/scanner to scanners/clients | | qrserver.com (public API) | Optional | Generate QR images (no credentials) |

> Important: Make sure your n8n instance URL is publicly accessible or use a tunneling/reverse proxy so webhooks can receive POSTs.

Installation Steps

Import the JSON into your n8n instance([https://n8n.partnerlinks.io/khmuhtadin). Configure credentials: Google Sheets OAuth2: Grant access to Google Drive & Sheets API (spreadsheets.readonly & spreadsheets). Gmail OAuth2: Grant send email scope (Gmail send). Update environment-specific values: Verify Google Sheet ID. Set the public base URL for ticket scanner clients to POST /v1/scanner. Customize settings: Event name/date/location (variables in Generate Ticket Data / Build HTML Email). Email sender address and subject line in Gmail node. Test execution: Use a sample POST to /v1/register with valid fields to create a registration. Mark a row as PAID and Email Sent = NO to trigger scheduled ticket generation. Simulate a scanner POST to /v1/scanner with the barcode JSON payload to test check-in.

Technical Details

Core Nodes

| Node | Purpose | Key Configuration | |------|---------|-------------------| | REGISTER (Webhook) | Accepts registration POSTs | Path: /v1/register | | Validate Input (Code) | Server-side validation | Validates nama, email, no_hp, jumlah_tiket, payment_method | | Get Participant (Google Sheets) | Check duplicate email | Filters Register tab by Email | | Store Data (Google Sheets) | Append registration | Tab: Register (gid=0) | | START (Schedule Trigger) | Finds paid registrations | Runs every 1 minute | | Get Rows (Google Sheets) | Reads Register rows | Reads full Register tab | | Filter Paid Not Sent (Filter) | Finds rows with Payment Status=PAID & Email Sent=NO | Filter node conditions | | Generate Ticket Data (Code) | Generate ticket IDs & QR payloads | Ticket ID format TL-YYYYMMDD-XXXX-N-HASH | | Generate QR Code (HTTP Request) | Calls qrserver.com to build PNG | URL: https://api.qrserver.com/v1/create-qr-code/?size=300x300&data=... | | Build HTML Email (Code) | Builds ticket HTML & embeds Base64 QR | Template contains ticket details & QR | | Send Email (Gmail) | Sends ticket email | To: recipient Email; Subject configurable | | Update Sheet (Tickets) | Append ticket rows | Tab: Tickets (gid=2010454173) | | Parse Data (Code) | Aggregates ticket IDs per email | Updates Register with combined ticket IDs | | SCAN TICKET (Webhook) | Check-in endpoint | Path: /v1/scanner | | Parse Barcode (Code) | Parses incoming scanner payload | Expects JSON in body.barcode | | Get Tickets (Google Sheets) | Lookup ticket by Ticket ID | Filters Tickets tab by Ticket ID | | Ticket Available? (If) | Validates existence & Checked In status | Branches to update or return error | | Update Ticket Status (Google Sheets) | Mark Checked In = YES | Sets Checkin TIme to scannedAt | | Checked IN / Already Checked IN (RespondToWebhook) | Respond payloads for scanner | JSON responses with status & metadata |

Workflow Logic

Registration:** Writes to Register sheet. A scheduled job picks up PAID rows where Email Sent = NO; for each row it generates one record per ticket, calls the QR API for an image, sends an email per ticket (multi-ticket support), then appends Tickets rows and marks Email Sent = YES by updating the Register sheet with combined ticket IDs. Check-in:** The scanner webhook accepts barcode JSON, extracts ticket_id, looks up the Tickets sheet, prevents duplicate check-ins by checking "Checked In" flag, and updates sheet with check-in timestamp on success.

Customization Options

Basic Adjustments

Email Template:** Edit Build HTML Email node to change branding, copy, or layout. Ticket ID Format:** Change code in Generate Ticket Data to alter prefix or hash length. Event Metadata:** Change event_name, event_date, event_location in code nodes.

Advanced Enhancements

Payment Gateway Integration:** Integrate with payment gateway (e.g., webhook from Stripe) to automatically set Payment Status = PAID — complexity: medium. Cloud Storage for QR Images:** Use cloud storage (S3) for QR images instead of base64-embedding — complexity: medium-high. Batch Email Provider:** Use batch email provider (SendGrid/Mailgun) for high-volume events to reduce Gmail quota risks — complexity: medium.

Troubleshooting

| Problem | Cause | Solution | |---------|-------|----------| | Invalid QR / scanner returns "Invalid QR code format" | Scanner payload not sending barcode JSON or malformed JSON | Ensure scanner POST body contains valid JSON string under body.barcode; validate payload in Parse Barcode node | | Ticket exists but cannot update | Google Sheets API auth / permission error | Reconnect Google Sheets OAuth2 credential; ensure the service account/user has edit access to the sheet | | Emails not sent | Gmail OAuth2 credential missing or Gmail API quota reached | Reauthorize Gmail credential; consider switching to SendGrid/Mailgun for large volumes | | Duplicate check-in allowed | Logic checking "Checked In" value mismatch (case/format) | Normalize the Checked In field values and use strict comparisons in Ticket Available? node | | Slow generation for many tickets | Sequential QR calls and sends | Use parallel execution or a dedicated email service; increase worker resources for n8n instance |

Use Case Examples

Scenario 1: Community Fun Run (200 attendees)

Challenge:** Manual QR generation and emailing takes ~3 hours. Solution:** After marking registrations as PAID, the scheduled job generates 200 QR tickets and emails them automatically. Result:** Ticket prep completed in <5 minutes; volunteer time reduced by ~3 hours.

Scenario 2: Regional Festival (2,000 tickets)

Challenge:** High volume requires reliable delivery and check-in speed. Solution:** Use this workflow but replace Gmail with a transactional email provider (SendGrid) and host n8n on a scalable instance. Monitor Google Sheets and email provider quotas. Result:** Automated delivery scales; on-site check-in handled via the /v1/scanner endpoint with near-instant validation.

Additional Information

Created by: Khmuhtadin Category: Event Automation, Ticketing Backend
Tags: google-sheets, gmail, qr-code, webhook, ticketing

Need custom workflows or help adapting this for your event? Contact us

Note: Import the JSON into your n8n instance to get started.

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