Diagnose a CSV that Looker Studio cannot read

Start with UTF-8 and a regular table

Looker Studio's file upload documentation calls for UTF-8, commas between fields, a header row, and the same columns in every row. It does not support line breaks inside data fields, even when they are quoted, so a normal spreadsheet export may need a deliberate check first.

• Invalid characters: convert an Excel or legacy-encoded export to UTF-8 after confirming the source encoding.
• File is Invalid: diagnose inconsistent column counts, separators, or a non-CSV file renamed with a .csv extension.
• Data is duplicated after adding files: remember that Looker Studio appends files and does not remove duplicate records.

• Diagnose CSV structure before changing values →Review column counts, quotes, empty rows, and duplicate rows in a separate workspace.
• Convert the CSV encoding or delimiter →Choose the source and output format explicitly before the destination import.
• Remove duplicate records before importing →Check duplicate IDs or email addresses before you create a second record.

Confirm the dataset schema before upload

Every file added to a Looker Studio dataset must have the same fields in the same order. Check that headers are unique, use only allowed characters, and do not change a live dataset's schema without creating a new dataset or removing the old files.

• Use commas as separators and quote commas that belong inside a field.
• Make sure every record has the same number of columns, including rows with missing values.
• Check the upload limits: 100MB per dataset, 100 uploads per dataset per day, and 2GB total storage per user.

• Find CSV rows with inconsistent column counts →Diagnose malformed rows before uploading them to a platform.
• Select the columns required by the import template →Remove export-only fields while keeping the original row count.
• Check or convert the CSV character encoding →Use this when Japanese, Korean, or accented text is garbled after export.

Diagnose and prepare a separate upload file

LocaCSV can diagnose and prepare the file format, but it cannot inspect fields already stored in Looker Studio or decide whether two rows are the same business event.

1. 1Keep the existing Looker Studio dataset unchanged and work from a copy of the export.
2. 2Open the copy in LocaCSV's CSV diagnostic workspace and review encoding, delimiter, header, and line-break findings.
3. 3If the input is a confirmed legacy encoding, convert it to UTF-8 in the format converter; do not guess from the country or application name alone.
4. 4Upload one small file to a test dataset first, then append only files with the identical header structure.

Verify the file before it becomes a dataset append

• The output is UTF-8 and the header contains unique field names.
• Every row has the same column count and no data field contains an unsupported line break.
• The output size stays below the dataset limit and the local row count is recorded.
• A test dataset shows the intended types and no duplicate append before production upload.

• Diagnose CSV structure before changing values →Review column counts, quotes, empty rows, and duplicate rows in a separate workspace.
• Remove duplicate records before importing →Check duplicate IDs or email addresses before you create a second record.
• Learn the general CSV split workflow →Choose a row count or target size while keeping the header in every output file.

Separate upload errors from data-model problems

If the file uploads but the report is wrong, inspect field types, date parsing, and append history. A structurally valid CSV cannot prove that a row is a new event or that a metric should be summed; use the dataset and report settings for those decisions.

• Remove duplicate records before importing →Check duplicate IDs or email addresses before you create a second record.
• Select the columns required by the import template →Remove export-only fields while keeping the original row count.
• Diagnose quoted newlines before a Jira import →Check record boundaries and the required Summary header before mapping fields.

Create a repeatable Looker Studio upload

Keep the verified header, encoding, row count, and dataset name in the refresh procedure so future exports can be checked before they are appended.