Few things are more frustrating than editing a shapefile in QGIS, saving it, and reopening to find columns missing, values blank, or field names mangled. The instinct is to blame QGIS, but in most cases the shapefile format itself is the culprit. A shapefile stores its attributes in a dBase III table — the .dbf sidecar file — and that format imposes rules that modern users constantly trip over.

The first classic cause is the ten-character field-name limit. dBase field names cannot exceed ten characters, so a field you named average_monthly_rainfall silently becomes average_mo when saved to shapefile. Related limits apply to data types: text fields are capped at 254 characters, and the format has no proper support for date-time values or very large integers. Values that don't fit are truncated or dropped without a loud warning.

The second classic cause is a missing or damaged .dbf file. A shapefile is not one file but a family: .shp for geometry, .shx for the index, and .dbf for attributes, at minimum. If the .dbf goes missing — because someone emailed only the .shp, or an export was interrupted — QGIS will still draw the geometry, but every attribute will be gone. Always move shapefiles as a set, ideally zipped.

To fix an existing problem, start by diagnosing. Open the layer properties and inspect the field list: truncated names point to the ten-character limit, while completely empty tables point to a .dbf problem. The Refactor Fields tool in the Processing Toolbox lets you rename fields and change types before saving, and running Check Validity on the geometry rules out corrupt features as the cause of missing rows.

For a long-term cure, consider migrating the layer to GeoPackage. GeoPackage is an open standard based on SQLite, stores many layers in a single file, and has none of the shapefile's name-length or type restrictions. In QGIS the conversion is one export away — and since CSV-to-shapefile conversions face the same attribute limits, GeoPackage is the better default target for new work too.

A short prevention checklist saves future headaches: keep field names under ten characters and free of spaces, back up the full file family before bulk edits, verify the attribute table immediately after every save, and share data as a zip containing all sidecar files. Most 'lost attributes' cases are really 'attributes the format never allowed in the first place' — once you respect the format's limits, or switch to GeoPackage, the problem disappears. And since attribute quality underpins every downstream step, calculating areas with the field calculator is another workflow that rewards intact, well-formed fields.