Methodology · reviewed August 20, 2026
What the CSV preflight checks—and what it cannot promise
Commerce CSV Preflight is a read-only screening tool for product CSV files. It reports structural and platform-specific risks before an import. It never rewrites the file, contacts a store, or certifies that an import will succeed.
1. The file stays local
The browser reads the selected file into memory. The release has no upload endpoint, cookies, account system, advertising code, or third-party tracker. Its Content Security Policy allows only the same-origin anonymous counter endpoint, which never receives the CSV, its name, size, contents, or diagnostics. The downloadable JSON report is created in the same browser.
The tool accepts UTF-8 CSV files up to 25 MB. It preserves cell text during analysis, including leading zeros in SKUs and other identifiers.
2. CSV structure is checked first
The parser handles quoted commas, escaped quotes, line breaks inside quoted fields, UTF-8 byte-order marks, and common delimiters. It reports malformed quotes, duplicate or blank headers, and rows whose field count differs from the header.
These checks are informed by RFC 4180. Real commerce exports vary, so a warning may identify a deliberate platform convention rather than an error.
3. Platform rules remain separate
For WooCommerce, the preflight checks product identity, duplicate SKUs and IDs, supported product types, publishing values, parent references for variations, sale-price relationships, and HTTP(S) image URLs. The rules follow the WooCommerce product CSV importer documentation.
The Shopify-to-WooCommerce migration profile reuses those source checks, groups rows by URL handle, verifies stable variant SKUs, and marks platform-dependent fields for manual mapping. Passing means the product CSV is ready for conversion planning—not that it can be imported directly or that the rest of the store has been validated.
For Shopify, the preflight understands current and backward-compatible product CSV header names. It checks titles and URL handles, option name/value pairs, variant-field dependencies, product status, booleans, prices, duplicate SKUs, and HTTP(S) image URLs. The rules follow the Shopify product CSV documentation and its common import issues.
4. Errors and warnings mean different things
- Error: a blocking structural or platform rule was detected. Do not import until it is reviewed.
- Warning: a risky or ambiguous value needs human review, but may be intentional.
- No blocking issues found: only the implemented checks passed. It is not a guarantee from WooCommerce, Shopify, or Brenes Revenue Studio.
Spreadsheet formula prefixes are warnings based on OWASP CSV injection guidance. The tool flags them; it does not alter the original values.
5. Safe import practice still matters
- Export or back up the current catalog before any bulk change.
- Test a small batch in the intended store environment.
- Review every error and warning against the platform documentation.
- Keep the original file and the generated report for comparison.
Platform formats can change. Brenes Revenue Studio maintains regression fixtures for both profiles, but merchants should treat the platform's current documentation and a store backup as the final safeguards.