How does CSV and Excel file cleaning work?

The 5 data cleaning steps

A guided flow to map, validate, fix and export your tabular data.

1. 1

   Upload and parse your file

   Drag and drop a CSV, XLS or XLSX file. Parsing automatically detects the delimiter (comma, semicolon, tab, pipe), columns and Excel dates. Your data stays in your browser: nothing is sent to any server.

2. 2

   Map and swap your columns

   Smart mapping matches your headers to the target fields (First name, Last name, Email, Phone, Date, Amount, Postcode, Reference). Swap any pairing from a dropdown, preview the final order and save a reusable template for your next imports.

3. 3

   Detect the classic data errors

   26 automatic checks review the most common data import traps: strict duplicates, email casing, stray spaces, unexpected data types, inconsistent phone numbers, ambiguous dates, broken encoding, scientific notation, unclosed quotes…

4. 4

   Fix in an interactive grid

   Faulty cells are highlighted row by row. Apply the suggested fixes in one click, or use the global formatting rules to normalise a whole column (ISO or DD/MM/YYYY dates, decimal separators, input masks, textual blanks).

5. 5

   Export the clean file

   Review the final sheet with the corrected data, then download your cleaned file as CSV or Excel, ready for database, CRM or ERP import.

Errors detected automatically

The full checklist of data quality issues verified on every import.

• Broken encoding

  Corrupted accented characters (wrong UTF-8 / Latin-1 encoding).

• Ambiguous dates

  DD/MM or MM/DD cannot be decided (US vs UK) inside a date column.

• Column shift

  Field count differs from the header: commas badly escaped inside text.

• Lost leading zero

  Phone numbers that lost their leading 0.

• Empty cells

  Empty cells breaking the table schema.

• Invisible spaces

  Leading, trailing or doubled spaces inside values.

• Email casing

  Mixed upper and lower case in email addresses.

• Unexpected types

  Text or “N/A” in an amount column: replaced with 0.00.

• Scientific notation

  Large numbers or IDs converted to 1.23E+12.

• High volume

  Large file: the analysis runs in batches.

• Line breaks

  Forced line breaks inside text cells.

• Heterogeneous null values

  Variants of empty values (NULL, NaN, -, none).

• Time zones

  Timestamps with different time-zone offsets.

• Non-standard delimiter

  Separator detected automatically: comma, semicolon, tab or pipe.

• Inconsistent phone numbers

  Phone numbers with spaces, dots or country codes: non-standard format.

• Truncated file

  File beyond the row limit of classic spreadsheets.

• Currency formats

  Currency symbols and mismatched thousand separators.

• Strict duplicates

  Strictly identical rows, or same id / email.

• Unclosed quotes

  Badly escaped or unterminated quotes in the CSV source.

• Rounded product codes

  Product codes or barcodes rounded to .0 or exponential.

• Truncated postal codes

  Four-digit postal codes: the leading zero was dropped.

Custom formats and local conventions

The formatting conventions that break imports most often, detected and fixable column by column.

• Non-standard dates

  DD.MM.YYYY, YYYY-MM-DD or textual formats such as "5 Feb 2026".

• Decimal separators

  Conflict between 1,234.56 (US/UK) and 1.234,56 (European).

• Input masks

  Dashes, brackets or spaces inside phone numbers, postcodes and IDs.

• Multi-line cells

  Forced line breaks or badly escaped nested quotes.

• Textual blanks

  Empty cells filled with "N/A", "-", "Unknown", "NULL", "NaN".

Application features

Everything Import Cleaner gives you, from upload to tracking your cleaning runs.

• Smart mapping and templates

  Header auto-detection, manual column swapping, unmapped columns kept, and saved templates for files coming from the same third-party software.

• Global formatting rules

  Apply a date format, decimal mode, input-mask cleanup or textual-blank strategy to one column or the whole file in one click.

• Custom formats tab

  A dedicated filter in the detection step isolates the custom formatting issues so you can handle them separately from classic errors.

• Interactive grid and traceability

  Every faulty cell is highlighted and typed, with manual editing and row-by-row issue tracking.

• Final sheet preview

  See the corrected columns and rows before downloading, with progressive row loading for large files.

• Large volumes, 100% local

  Batch processing for large files, truncation alerts, and analysis running entirely in your browser: no data leaves your device.

• Dashboard and history

  Review the history of your cleaned files, the number of fixed errors and download tracking per language.