> ## Knowledge Base Index
> Fetch the complete knowledge base index at: https://gs1assistant.crisp.help/sitemap.xml
> Use this file to discover available pages before exploring further.
> Pure-Markdown content can be obtained by appending a '.md' suffix to the content URLs listed in the sitemap (without the trailing slash).

# Before You Install: Do You Have a GS1 Company Prefix?

Before you can use GS1 Assistant, you need a GS1 company prefix.

Your prefix is what allows you to create valid GTINs (UPC/EAN barcodes) for your products.

Without a prefix, the app cannot assign GTINs.

### What is a GS1 company prefix?

A GS1 company prefix defines a block of GTINs assigned to your company that start with a given string of numbers (the prefix) issued to your business by an official GS1 organization.

Every GTIN you create starts with this prefix. Marketplaces like Amazon, Google Shopping, and Walmart use it to verify that the barcode belongs to your business.

In the example below, if your prefix is `506502397`, the product number is `800`, and the check digit is `7`, the GTIN will look like `5065023978007`.

![GS1 company prefix example](https://leftfootsoftware.github.io/Help-GS1-Assistant/v1/assets/en/prefixexample.png)

### How many GTINs can you create?

The length of your prefix determines how many GTINs you can generate.

Most Shopify merchants purchase prefixes that support:

- 10 GTINs
- 100 GTINs
- 1,000 GTINs

If you’re unsure where to start, a 100 GTIN prefix is usually enough for many small to mid-sized stores.

Here’s an example of how prefix length determines the number of GTINs available:

![Prefix length and available GTINs](https://leftfootsoftware.github.io/Help-GS1-Assistant/v1/assets/en/availableGTINs.png)

> **Important: GS1 Assistant does not provide prefixes**
>
> GS1 Assistant manages the GTINs linked to your prefix.
>
> It doesn’t generate free barcodes or sell GTINs.
>
> The only exception is GS1 US customers, who can purchase a prefix through the app directly from GS1 US.

![Purchase a GS1 US prefix](https://leftfootsoftware.github.io/Help-GS1-Assistant/v1/assets/en/GS1USprefix.png)

### How to check if you already have a prefix

#### Option 1: Check your GS1 account

Log in to your GS1 member organization portal.

Your prefix should appear in your account dashboard.

Examples:

- GS1 US
- GS1 Germany
- GS1 UK

#### Option 2: Check your existing barcodes

If you’ve already assigned GTINs to products before, the first digits usually represent your prefix.

Example:

- GTIN: `00614141123457`
- Prefix: `0614141`

### My prefix shows as ‘Invalid’ in the app

If you recently:

- purchased a prefix
- renewed your membership

it may take some time for GS1 databases to update.

In most cases:

- wait 24 hours
- click **Start Scan** to refresh the app
- try again

If your prefix still shows as invalid after 48 hours, contact support and the team can manually verify it.

### If you don’t have a prefix yet: where to get one?

You must purchase a prefix from an official GS1 organization.

Your GTINs will still work globally regardless of which GS1 organization you purchase from.

![Official GS1 organizations](https://leftfootsoftware.github.io/Help-GS1-Assistant/v1/assets/en/GS1organizations.png)

### UPC vs EAN: What should you know?

Prefixes from:

- GS1 US
- GS1 Canada

support UPC (12-digit) barcodes.

Most other GS1 organizations issue EAN (13-digit) barcodes. Amazon, Google Shopping, and Walmart accept both formats.

However, some physical US retailers still require UPC barcodes due to antiquated systems.

If you plan to sell through US retail stores, keep this in mind before choosing a GS1 organization.

> **Tip:** Different GS1 Member Organizations have different pricing models, and some allow businesses outside their region to register as well. If you don’t need UPC codes, you can buy from GS1 Germany or GS1 UK, which are more cost-effective.

Some websites sell low-cost barcodes that are not registered to your business.

Marketplaces now verify GTIN ownership against GS1 records. If the barcode belongs to another company, your listings may be rejected.

GS1 Assistant may also flag these codes as invalid.

If you already have some of these on your products, see the article: *How to Remove Invalid or ‘Not GTIN’ Barcodes in Bulk to clean them up.*

### Once you have your prefix

After getting your prefix, you can connect it to GS1 Assistant and start assigning GTINs to your Shopify products.

If you’ve already assigned GTINs manually before, you can also choose where the app should begin assigning new numbers to avoid duplicates.

### Useful links

- [GS1 US membership page](https://www.gs1us.org/who-we-are/membership)
- [GS1 Germany portal](https://www.gs1.org/locations/germany)
- [GS1 UK membership page](https://www.gs1uk.org/about-us/membership)