The preview validates your file before anything is saved, so you can fix problems without creating bad trades. Fix errors in this order — each step removes the next layer of noise.
1. Required column mapping
Make sure every required field (Date, Market, Side, Result, and any required custom columns) is mapped to a column in your file. Unmapped required fields block the import.
2. Unknown values
When MYTH doesn't recognize a value, map it to a known one — for example long and short to Buy and Sell, or a market code to one of your active markets. Activate the market first if it's missing.
3. Data formatting
Fix rows flagged for formatting: inconsistent date formats, non-numeric results or RR, or empty required cells. Correct them in the source file and re-upload, or adjust the mapping.
Common causes
Mixed date formats in the same column
A market in the file that isn't active in your account
Required custom columns left empty
Extra header rows or blank rows in the file
Only rows that pass validation are imported. Resolve all errors, re-check the preview, then import.