Zapier vs. Custom Google Apps Script: A Decision Guide

"Should we use Zapier?"

We get asked this in every single discovery call. And honestly? The answer is often yes.

We are developers who build custom automation, but we aren't anti-Zapier. Zapier is an incredible tool. But it has a "ceiling." If you hit that ceiling, it becomes expensive, slow, and frustrating.

Here is the decision framework we use to advise our clients.

The Comparison at a Glance

When to Use Zapier

Zapier excels at connecting different apps together with simple logic. Use it if:

• You're wiring between external apps (Salesforce to Slack, Pipedrive to Trello)
• Your workflow is just "if this happens, then do that"
• Volume is low (5 times a day = cheap)
• You need it running today

It's solid for quick prototypes and simple connectors.

When to Use Custom Apps Script

Build with Apps Script if:

• You live in Google Workspace (Sheets, Drive, Docs, Slides are your home)
• You need loops or complex math (scan 1,000 rows, calculate interest, email only the unpaid ones)
• Volume is high (processing 5,000 rows weekly makes Zapier hundreds of dollars/month; Apps Script is free)
• You want a custom interface (a button in Sheets that says "Generate Report")

This is for core business operations and high-volume work.

The "Success Tax"

The biggest hidden cost of tools like Zapier is the Success Tax. The more successful you become (more leads, more sales, more data), the more they charge you.

With Custom Apps Script, there is no success tax. You pay once to build it, and it scales with you to infinity.

In Short

Use Zapier for quick connectors between SaaS tools. Use Apps Script to build the core operations your business runs on.

Unsure? Book a discovery call and we'll tell you straight, even if that means recommending Zapier.