CSV or XLSX for a roster import: which should you use?

When a roster is already planned in Excel, there is no universal rule that says “always export CSV” or “always upload the workbook”. Both can work for publication, and each can hide a different type of mistake. The important question is: which file gives you a faithful, inspectable view of the people and dates you intend to publish?

What a CSV preserves

A CSV is a text table: one row per line, fields separated by commas and quoted where needed. It has no worksheets, colours, merged cells, formulas or workbook metadata. That simplicity makes it useful for checking the actual values that an importer will read. It also means an exported date may be written differently from the date you saw formatted in Excel.

If you export CSV, open the exported file, not just the original workbook. Confirm that employment numbers have not lost leading zeroes, names with commas remain in one cell, and dates look like dates. Save as UTF-8, especially if names or locations contain accents or non-ASCII characters. A text field that looks blank but contains hidden whitespace is not a valid worker identifier.

For example, 00042 is not interchangeable with 42 if the employment-number system treats them as different identifiers. Check a few records at the start, middle and end of the file; a perfect-looking first row cannot prove the whole export is correct.

What an XLSX preserves

An XLSX can contain several sheets, which may include draft versions, summaries and the actual roster. Select the intended worksheet in the import flow. XLSX also retains cell types and formulas, but the importer does not calculate those formulas. It uses saved results where available and warns about results that are missing or might be stale. If a workbook has been generated automatically without cached values, open, recalculate and save it in a spreadsheet application before trying again.

Formatting is not the same as data. A highlighted “night shift” cell might mean something to a person reading the sheet, but a parser needs an actual shift value. Merged headings and notes can push the true names or dates away from the first row or column. Review the mapping rather than assuming every project uses a fixed template.

A practical decision

If your source has…	Check this before uploading
One simple table and no essential formulas	CSV may be easier to inspect. Use UTF-8 and confirm dates and leading zeroes after export.
Several worksheets	XLSX lets you choose a sheet; verify you have selected the current roster rather than a draft.
Formula-derived shifts or dates	XLSX retains formula cells, but requires saved results; recalculate and inspect any warnings.
Merged headers or decorative sections	Either format may need manual field/date mapping and source cleanup.

CSV can also be smaller to reason about, but not necessarily smaller on disk: XLSX compresses repeated status values. The signed-in app accepts large bounded imports; your Hostinger/PHP upload configuration must still allow the file size. The public interactive demo uses the real importer with smaller CSV/XLSX limits and temporary server-side storage; use a non-sensitive test file, not a live roster. A complex XLSX may exceed those limits.

Whichever format you choose, the review is the gate

After upload, start with the action list and confirm the people, date range, status meanings, source-position identifiers, exclusions and duplicate groups. Unfamiliar non-empty daily labels default to their cleaned source text and require confirmation; a blank mapping retains them. Matrix layouts can use physical source identifiers, but shift lists require employee identifiers. Refresh after edits and compare total counts, not just the first-100-entry sample. If the result does not match the workbook, correct it before publication.

For a complete pre-release process, use the upload checklist and the explanation of formula results. Neither file format removes the need for a human to approve the version workers will use.

Questions people ask

Is XLSX always the safer choice when a workbook has formulas?

Not automatically. XLSX retains worksheets and formula cells, but the importer reads their saved results, not a fresh calculation. Recalculate, save and inspect a few known assignments before upload. A checked CSV export may be simpler for a single sheet, provided its dates and identifiers survive conversion.

Can changing the file extension fix an unsupported layout?

No. Renaming a workbook from .xlsx to .csv does not convert its contents. Export the intended sheet properly, then confirm the preview identifies the right people, dates and shifts.