Compare two supplier CSV files before you update stock or prices

A small, practical pre-import check for merchants and operations teams. This guide does not connect to Shopify, your store or any supplier.

When you receive an updated product export, compare it with the previous version using a stable SKU or product key. A row-by-row comparison is unreliable if the supplier reorders the file. Keep both originals unchanged and make a separate exceptions report before deciding what to import.

A fictional three-product example

These invented records demonstrate what a review report should flag. They are not customer data or results from a paid job.

SKU	Previous file	New file	Review flag
A001	Qty 10; £9.50	Qty 0; £9.50	Stock dropped to zero
A002	Qty 3; £15.00	Qty 3; £17.00	Price increased £2.00
A003	Qty 5; £8.00	Absent	Missing from new file
A004	Absent	Qty 8; £12.00	New SKU

A missing SKU is a review item, not proof that a product is discontinued. An unexpected price or quantity change is a warning, not an instruction to change your store automatically.

Five checks worth making

Choose the matching key: confirm that the SKU is stable and unique in both exports. Flag duplicate or blank keys rather than choosing a row at random.
Count added and missing SKUs: compare key sets, not row positions. Check whether supplier pack sizes or SKU formats changed.
Compare agreed fields: stock quantity, unit price or another named column. Preserve currency and units; do not silently convert ambiguous values.
Review unusual changes: zero stock, large price movements, missing values and unexpected row-count differences deserve attention.
Export exceptions separately: keep original files intact and obtain approval before importing anything into a live store.

Shopify inventory CSV: match the correct stock state and location

If one file is a Shopify inventory CSV, first check which export format and inventory state it contains. Shopify's All states export separates stock by location and includes fields such as Available, Committed, On hand (current) and On hand (new). These are not interchangeable quantities: Available represents stock that can be sold, while On hand (current) is the export-time snapshot used for import safety checks.

Keep the exported original untouched. A discrepancy review is not an import-ready inventory update. Do not fill On hand (new) from a comparison report without your own stock review and Shopify's documented import procedure.
Check the location as well as the SKU. A SKU can occur on more than one location or bin row. A one-key comparison by SKU alone may falsely report duplicates or changes. Our £19/£29 starter packages assume one genuinely unique agreed key; multi-location matching needs a separate feasibility and scope review.
Specify the source of each file. A Shopify product CSV, a Shopify inventory CSV and a supplier stock list can have different schemas. State the export type, approximate rows, location count and quantity field before requesting a quote. Use fictional or fully redacted examples initially.

Reference: Shopify's official inventory CSV export/import documentation. Nilo Works is independent of Shopify and does not connect to stores, change inventory or guarantee that a reviewed file is safe to import.

Try the free check — or request a small fixed-scope comparison

Our free browser-local CSV checker helps find keys present in one file but not the other. It does not compare changed quantities or prices, and its documented file/row limits apply.

For a separate checked discrepancy report, our CSV Inventory Reconciliation starts at £19 for two ordinary CSV files with up to 150 rows combined, one unique matching key and up to two fields (for example quantity and price). A £29 standard option covers up to 500 rows combined and three fields. Both are subject to a written scope and delivery agreement before payment.

Try free key checker Build a private quote brief

Deliverables for an agreed paid task: separate discrepancy CSV files, a short counts-only audit, and sample checks. No automatic Shopify or supplier integration, live stock editing, fuzzy matching, or guarantee of import compatibility.

Before requesting a quote

Send the two file formats, approximate row counts, the key column, the two or three fields you want checked, and your deadline. Start with fictional or fully redacted rows. Do not email passwords, customer lists, payment details or confidential supplier records before suitable handling is agreed.

Nilo Works uses AI-assisted preparation and checks outputs against agreed rules. Portfolio examples are synthetic, not testimonials or previous paid commissions.