🔧 Event ticketing backend: auto QR tickets with Google Sheets & Gmail
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Description
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.
Screenshot 20251005 at 15.01.48.png
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/registerreceives 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 | 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/registerwith 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/scannerwith the barcode JSON payload to test check-in.
- Use a sample POST to
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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đź”— Nodes Used
Google Sheets, HTTP Request, Webhook, Gmail, Schedule Trigger, Filter
đź“Ą Import
Download workflow.json and import into n8n:
Workflow menu → Import from File