Errors in WeTransform aren't bugs — they're features. They mean WeTransform is doing its job: comparing the incoming data against what you defined as valid, and flagging everything that doesn't match.
But for errors to appear, your target format needs to be properly configured. No constraints = no errors = no protection.
🎯 The principle
When a file is transformed, WeTransform compares every value in every column against the constraints you defined in your target format. If a value doesn't comply, the cell turns red in Finalize and an error is counted.
If you have no constraints, every value is considered valid — even obviously wrong ones. That's why setting up constraints is the most important step before sharing your format with clients.
🔒 What constraints to set up
In your target format, open any column and configure its constraints. The most impactful ones are:
📝 List of valid values — the most powerful constraint. If your column only accepts a specific set of values (country codes, product categories, appointment types, statuses), define them here. Any value outside the list triggers an error — and the AI can map them automatically.
✳️ Mandatory — any row where this column is empty will be flagged as an error. Essential for fields your system can't function without.
🔢 Data type — setting a column as Number, Date, Email, or URL means any value that doesn't match the type will error. For example, "12,50" in a Number column configured with "." as separator will flag as invalid.
📏 Length constraints — minimum or maximum number of characters. Useful for codes, identifiers, or fields with fixed-width requirements (EAN-13, SIRET, etc.).
📅 Date format — if you expect DD/MM/YYYY, any other format will trigger an error. This catches the classic MM/DD/YYYY vs DD/MM/YYYY confusion.
💡 Use the AI to write advanced constraints. For complex validations (regex patterns, cross-column conditions), describe what you need in plain language in the constraints panel — WeTransform generates the rule automatically.
⚖️ Decide how strict you want to be
In your target format's General Settings → File Settings, you can configure whether you accept files that contain errors or require them to be completely error-free before submission.
Accept files with errors — the user can submit even if some rows have errors. Useful for internal workflows where you review and fix manually.
Require error-free files — the Submit button is locked until all errors are resolved. Recommended when embedding WeTransform in your platform or sharing with external clients.
👉 What to do next