Shopify SKU generator for every variant, with an import-ready CSV

What a SKU is, and what it isn't

A SKU (stock keeping unit) is your own code for one sellable item. On Shopify it sits on the variant, so a shirt in three sizes and four colours has twelve SKUs. It's optional: Shopify says "SKUs aren't required", and lists better inventory tracking, accurate reporting, easier fulfillment and third-party integrations as the reasons to use them¹.

A barcode is a different field. It holds a number other systems recognise: Shopify accepts GTIN (8, 12, 13 or 14 digits), UPC, EAN, ISBN, ASIN or a custom value up to 255 characters, and up to 20 barcodes per product or variant². You make SKUs up. GTINs you get from GS1 or your supplier, and Google Shopping and marketplaces match products on them. The GTIN glossary entry explains the identifier, and the barcode field guide covers which one each product needs. Don't put a SKU in the barcode field or a GTIN in the SKU field.

Shopify's SKU rules

Shopify's SKU page sets out four rules¹. First, every SKU should be unique: "SKUs within your Shopify admin must be unique and no two product variants should include the same SKU." Shopify doesn't block a duplicate. It shows a warning on the variant and notes that duplicates cause trouble with integrations and inventory tracking.

Second, keep them short: "no more than 16 characters", and as few as 4 to 8 for a small catalog. The generator warns above 16 by default. Third, avoid a format where 0 and 1 can be confused with O and I. Tick "Leave out the letters O and I" and automatic codes drop them, so Olive becomes LVE and Ivory becomes VRY. Fourth, skip special characters, symbols and spaces, which Shopify says "can cause search problems". Dashes and underscores are fine for separating attributes. The generator offers those two, or no separator at all.

A good SKU structure

Go from general to specific: brand, then product, then the options that make each variant different. Anyone reading NR-LSH-S-BLA on a bin label can tell it's the small black linen shirt without looking anything up. With brand code NR, the product "Linen Shirt" and three sizes by four colours, the default pattern gives:

The product code comes from the title's initials, topped up from the last word (Linen Shirt → LSH). Option codes are the first three letters of each value. If you'd rather number products than abbreviate them, turn on the sequence segment and turn off the product code: the same shirt becomes NR-001-S-BLA, and the next product in the list gets 002. "Per product" gives every variant of a product the same number; "per variant" counts every row.

Abbreviations collide. With two-letter codes, Black and Blue both start BL. The generator keeps the first one and moves the next to other letters of the same word, in order: Black = BL, Blue = BU, Brown = BR. Every change is listed under the results so nothing moves silently. Codes you set yourself in the abbreviations box are never changed; if two of yours clash, the tool tells you.

Things to leave out of a SKU: the price (it changes), the supplier's code (keep that in a separate field or metafield), and anything you'd be tempted to change later. A SKU that changes breaks every app, 3PL and spreadsheet that stored the old one.

Why SKUs matter on Shopify

A store can run without SKUs. They start to matter the moment anything outside Shopify gets involved: warehouse and 3PL systems, inventory and ERP tools, marketplace connectors and accounting exports often match products on SKU. Shopify's own note is that "many apps and services require SKUs to sync inventory"¹. Reports and exports are also easier to read with a code that means something. The time to set a scheme is before the first integration, because changing SKUs later means updating every system that stored them.

Common SKU mistakes

The most common one is a code that a spreadsheet rewrites. Excel drops leading zeros, so 00123 becomes 123, and it keeps only 15 significant digits, so a 16-digit numeric SKU loses its last digit⁸. A code like 1E5 reads as scientific notation and becomes 100000, and 3-12 turns into a date. The checks flag all four. Starting every SKU with a letter avoids the lot.

• Reusing a retired SKU for a new product. Sales history and reports then mix the two.
• Spaces and punctuation inside the code, which Shopify warns cause search problems.
• Two formats in one catalog: half as SHIRT-BLK-S, half as BLK-SHIRT-SMALL. Sorting and picking get harder. Pick one pattern and generate every SKU from it.

How to bulk-update SKUs in Shopify

Shopify documents two ways: "you can use the bulk editor or import them using a CSV file"¹. For a few dozen variants, the bulk editor is quicker: select the products, choose Bulk edit, and add the SKU column from Columns if it isn't showing. Each variant gets its own row⁶. For a whole catalog, use a CSV:

1. Export your products from the Products page. Keep this file as your backup.
2. Choose "Paste rows or a Shopify export" above and paste the file's contents or open it. The generator reads the URL handle, Title and Option columns. Tick "Keep SKUs that are already filled in" if you only want to fill the gaps.
3. Set the pattern, fix anything the checks flag, and download "Shopify CSV: update SKUs".
4. Import it from the Products page and select "Overwrite products with matching handles". Try one product first.

The update file holds only Title, URL handle, the Option name and value columns, and SKU. That's deliberate. Shopify's overwrite rules are strict: a column you leave out keeps its current values, but a column you include with a blank cell is overwritten as blank³. Shopify also warns that sending SKU without the Option1 columns deletes the variant option⁵, and that changing an Option value "deletes existing variant IDs, and creates new variant IDs"³, which breaks apps that stored those IDs. So the generator writes your option values back exactly as they came in. Keep every variant of a product in the file, and don't edit option values in the same import.

File rules from Shopify: UTF-8 with LF line endings³, no larger than 15 MB (split bigger catalogs), and don't sort the export in a spreadsheet editor before re-importing, which can separate products from their images⁵. The generator writes UTF-8 with LF line endings. If you open the file to check it, Shopify recommends Google Sheets³; Excel will rewrite the codes described above when it saves.

The CSV the generator writes

Column names follow Shopify's current product template, which renamed the older columns: "URL handle" instead of Handle, "Option1 name" and "Option1 value", and plain "SKU" instead of Variant SKU⁴. The generator also reads exports that still use the old names. For new products, the file adds a Status column set to draft on every row. Shopify publishes products as active when the column is missing, and a present Status column needs a value³, so drafts give you time to add prices and photos before anything goes live. The first rows of the linen shirt example:

Title,URL handle,Option1 name,Option1 value,Option2 name,Option2 value,SKU,Status
Linen Shirt,linen-shirt,Size,S,Color,Black,NR-LSH-S-BLA,draft
,linen-shirt,Size,S,Color,Blue,NR-LSH-S-BLU,draft

The product title goes on the first row of each product only, and the URL handle repeats on every variant row, the layout Shopify describes for products with variants³. Shopify allows up to three options and 2,048 variants per product, though it notes some themes, apps and channels stop at 100⁷. The generator warns when one product goes over 2,048.

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