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Data Health Check

Open a CSV or Excel table to get a list of problems — blanks, duplicates, spelling variants, garbled text and more — ranked by severity, a 0–100 health score and a profile of every column. Click a finding to see the affected rows; fixable problems link to the right tool.

On-device・No upload

Your files and input are processed only inside your browser on this device and are never uploaded to our servers.

Drop a file here

or

Files are processed in this browser on your device and never uploaded.Accepts: Excel (.xlsx) / CSV / TSVUp to 100 MB per filePaste (Ctrl+V) also works

How to use

  1. Drop a CSV, TSV or Excel (.xlsx) file, or click “Choose files”. CSV encodings are detected automatically.

  2. For workbooks, pick the sheet to check. Turn the header switch off if the first row is data.

  3. Read the health score and the number of findings per severity (High, Medium, Low, Info). “How the score is calculated” shows every deduction.

  4. Click “Show affected rows” on any finding to see the rows and highlighted cells.

  5. For fixable problems, follow the button (e.g. “Fix with Excel Cleanup”) to the matching tool.

  6. Save the findings and the column profile as an Excel or CSV report.

What it does

32 checks tuned for real business data

Blanks, empty rows and columns, duplicate rows, duplicate IDs and headers, mixed types, numbers stored as text, mixed date formats (incl. Japanese eras), impossible dates, spelling variants (width, spaces, kana, company suffixes), leading/trailing spaces, invisible characters, line breaks, mojibake, Excel errors (#N/A …), exponent notation and lost leading zeros, e-mail/phone/postal formats, outliers and ragged CSV rows.

See the affected rows instantly

Each finding shows a count and examples (with spaces and zero-width characters made visible). One click lists only the affected rows with their original row numbers, problem cells highlighted.

A score you can trace

The 0–100 score subtracts severity points (High 10, Medium 5, Low 2) scaled by the share of rows affected. The deduction table shows every point; outliers and other info-level findings never lower the score.

Profile of every column

Inferred type (integer, number, date, e-mail, phone, postal code, URL, numeric code, text), fill rate, distinct values, min/max/mean/median, date range, most frequent values and a text-length histogram.

Fix links and a downloadable report

Spacing, width and date issues link to Excel Cleanup, duplicates to Excel Deduplicate, garbled text to CSV Encoding Fix. Save the findings and column profile as Excel or CSV.

Use cases

  • Check a CSV from a partner for format errors and garbled text before importing it into your system
  • List blanks, duplicate entries and invalid e-mails or phone numbers in a customer list
  • Find out why totals do not add up — numbers stored as text, spelling variants, mixed widths
  • Spot columns whose leading zeros or long numbers Excel will destroy when the CSV is opened
  • Get a quick overview of types, fill rates and value ranges of an unfamiliar dataset

Supported formats

Input

CSV (.csv)TSV (.tsv / .txt)Excel (.xlsx / .xlsm)

Output (report)

Excel (.xlsx with findings, profile and summary sheets)CSV (UTF-8 with BOM, Shift_JIS, …)

Capability matrix

FeatureSupportNotes
Blanks, duplicate rows/IDs, empty rows and columnsSupported—
Mixed types, numbers stored as text, mixed date formatsSupported—
Spelling variants, spaces, width, invisible characters, line breaksSupportedVariants checked in columns with ≤ 300 distinct values
Garbled text, Excel errors, lost leading zeros, exponent notationSupported—
E-mail, phone and postal code format checksPartialPhone and postal codes: Japanese formats only; existence is not verified
Outlier detectionPartialStatistical hint based on the interquartile range
Column profile (type, fill rate, statistics, top values)Supported—
Automatic fixingNot supportedFix with the linked tools
Custom rules (required columns, value ranges)Not supported—
Legacy Excel (.xls)Not supportedRe-save as .xlsx in Excel first

Limits & notes

  • Up to 100 MB and 3 million cells per file, one sheet at a time.
  • Affected rows are listed up to the first 5,000 per finding (the report lists the first 50 row numbers per finding).
  • Column types are inferred from the values, so very small tables or tables without a header may be classified imperfectly.
  • Outliers are a statistical hint only and never lower the score.
  • Formatting, data validation and formulas themselves are not checked; formulas are checked by their calculated values.

Privacy & safety

Reading, checking and building the report all happen in your browser. Your data is never sent to or stored on a server.

FAQ

How do I check the data quality of a CSV file?
Just open the file. Blanks, duplicates, mixed types, spelling variants, garbled text and more are listed by severity, and every finding can show its affected rows.
How is the health score calculated?
Start at 100 and subtract severity points (High 10, Medium 5, Low 2) × an impact factor between 0.4 and 1.0 for every finding. Problems affecting 20 % or more of the rows count fully; info-level findings such as outliers are not deducted.
How are spelling variants detected?
Values that become identical after unifying spaces, full-/half-width characters, hiragana/katakana and letter case are grouped, and the less common spellings are counted as variants. In company-name columns, suffixes such as “株式会社” or “(株)” are unified too.
Does it detect mixed date formats, including Japanese eras?
Yes. It distinguishes notations such as “2024/05/10”, “2024-05-10”, “2024年5月10日” and Japanese eras like “令和6年5月10日”, and reports dates that differ from the main format as well as impossible dates.
Can it fix the problems it finds?
This tool only diagnoses. Each fixable finding links to the right tool: Excel Cleanup for spacing, width and dates, Excel Deduplicate for duplicates, and CSV Encoding Fix for garbled text.
Is my data uploaded?
No. Everything runs in your browser and your data never leaves your device.

Related tools

CSV Encoding Fix

Convert CSV files that show garbled text in Excel to UTF-8 with BOM or Shift_JIS, with automatic encoding detection. Mojibake that was already saved, such as “日本語”, can usually be restored too.

CSV Studio

Open CSV files that are slow or garbled in Excel and view, search and edit them right away in your browser. Combine, split and save as CSV (UTF-8 with BOM, Shift_JIS), Excel or JSON on one screen.

CSV, JSON, XML & Excel Converter

Convert between CSV, TSV, JSON, JSON Lines, XML and Excel (.xlsx) by pasting or opening a file. Values stay as text by default, so zero-padded postal codes, phone numbers and long IDs are never changed. Everything runs in your browser; your data is not uploaded.

Excel Cleanup

Tick what to fix and clean up spaces, character widths, dates and numbers across a whole Excel or CSV file at once. Changed cells are highlighted, and you can save as Excel or CSV.

Excel Compare

Load an old and a new Excel or CSV file to see added, removed and changed rows, with every changed cell shown as “old → new”. Save the result as a colour-coded Excel report or CSV.

Excel Deduplicate

Find duplicate rows in an Excel or CSV file by the columns you choose, ignoring the variations you choose, then remove them or merge each group into one row. Review every group, change which row survives, and save as Excel or CSV.

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