Validate Excel Files Online
Validate Excel file structure in your browser. Check null counts, distinct values, and data types for every column — no upload required.
How to validate Excel files
- Drop your file onto the upload area. The report starts as soon as the file has loaded. There are no settings.
- Read the four summary cards: total rows, columns, null-heavy columns and all-null columns.
- Scan the Column Report table for each column's detected type, null count, percentage of nulls and number of distinct values.
- Check the warnings under the table. Columns that are entirely null are flagged in red and columns that are more than half null in amber.
Your file is processed locally in your browser and is never uploaded. The free limit is 50 MB per file; larger files work if your device has the memory for them.
Worked example
A clinic exports a week of appointments before loading it into a reporting database. The analyst wants to know which fields are reliable before writing any queries.
Input (Excel)
Excel workbook, first sheet (Sheet1)
| patient_ref | clinic | appointment_date | no_show | notes |
|---|---|---|---|---|
| P-104 | Eastside | 2026-06-02 | false | NULL |
| P-221 | Eastside | 2026-06-02 | true | Called to rebook |
| P-104 | Harbour | 2026-06-09 | false | NULL |
| P-318 | NULL | 2026-06-11 | false | NULL |
| P-450 | Harbour | 2026-06-11 | true | NULL |
Settings
- No settings. The report is generated when the file loads.
Result
| Column | Type | Nulls | % Null | Distinct |
|---|---|---|---|---|
| patient_ref | VARCHAR | 0 | 0.0% | 4 |
| clinic | VARCHAR | 1 | 20.0% | 2 |
| appointment_date | DATE | 0 | 0.0% | 3 |
| no_show | BOOLEAN | 0 | 0.0% | 2 |
| notes | VARCHAR | 4 | 80.0% | 1 |
The summary cards read 5 rows, 5 columns, 1 null-heavy column and 0 all-null columns. notes is flagged in amber at 80% null. patient_ref has 4 distinct values in 5 rows, which shows P-104 appears twice, so it cannot be used as a unique key. Distinct counts ignore nulls, which is why clinic shows 2 rather than 3.
Working with Excel files
The first sheet is converted to text as Excel displays it, then types are detected from that text. That affects the report. A column of amounts formatted as currency, such as $1,200.00, is likely to show as VARCHAR because the currency symbol and separator travel with the value. Cells with a date format show as DATE or TIMESTAMP, whatever style they display. A date column that reports as a number was left in General format, and one that reports as VARCHAR was typed as text.
Blank cells are counted as nulls. A column that is 100% null with a generic name is usually not your data at all. It tends to be an empty column inside the sheet's used range, often left behind by formatting. In the same way, empty rows inside the used range raise the null percentage of every column. If all columns show the same small null count, look for blank spacer rows in the sheet. Only one row is used as the header. If the sheet has a two-row header, the second row is read as data. That text row can turn numeric columns into VARCHAR in the report, which is a quick way to spot the problem.
Frequently Asked Questions
Why does my Excel number column show as VARCHAR?
The values are read as displayed. Currency symbols, thousands separators, percentage signs or a stray text cell turn the whole column into text. Set the cells to a plain Number format in Excel and validate again.
Does the validation check all sheets in my workbook?
No. Only the first sheet is read and reported on.
Does Validate change or download my file?
No. It only produces the on-screen report. Nothing is modified and there is no download.
What counts as a null-heavy column?
Any column where more than 50% of values are null. The Null-heavy card counts all-null columns too, so a column that is 100% null is included in both cards.
Do distinct counts include nulls?
No. Distinct counts only non-null values. A column with values A, B and some nulls shows 2.
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