Dummy Excel File Generator (XLSX)
Every dummy Excel file is an .xlsx workbook with one sample sheet, from 4 KB to 50 MB, exact to the byte.
Sample XLSX files, ready to download:
One click, exact size (1 KB = 1,024 bytes), default options, built in your browser.
A dummy Excel file is a real .xlsx workbook with one sample sheet, made for testing. Download one free at the exact size you need, from 4 KB to 50 MB. It is built in your browser, so you can test spreadsheet uploads, file type validation and storage limits without exposing real business data.
How we check it: every generated file must be exactly the size you set and pass our own ZIP and CRC-32 checker, JSZip, Info-ZIP unzip -t and 7-Zip, plus the required OpenXML parts; the last run on 21 October 2026 passed 155 of 155 runs across 17 formats (how the files are made and checked).
Download a dummy Excel file by size
Each page below has a ready-made Excel test file, its exact byte count and the limits it is closest to.
What is inside a dummy Excel file
An .xlsx file is a ZIP archive of XML parts. Here is what the generated one contains (how we build and check these files):
- One worksheet named Sheet1 with a header row (ID, Name, Status, Amount) and two sample records: 1001 Alpha Corp Active 450.00 and 1002 Beta Systems Verified 825.50.
- The standard package parts: [Content_Types].xml, package and workbook relationships, workbook.xml and sheet1.xml.
- A filler part, padding.dat, holding zero bytes. It carries the extra size, and everything is stored uncompressed so the file reaches your exact byte count.
- The content does not grow with the size. Row count stays at two records, so use the dummy CSV page when you need many rows.
What a dummy Excel file is used for
Spreadsheet upload testing
Verify your app accepts .xlsx uploads, enforces size caps, and shows a sensible error when a workbook is too large.
File type and signature validation
The file starts with the ZIP signature (PK) and uses the OpenXML spreadsheet MIME type, so it checks both extension and magic-byte validation.
Storage and transfer limits
Confirm gateways, proxies and cloud storage accept Excel attachments up to your maximum.
Safe demo files
Attach a synthetic workbook to bug reports and demos instead of a real financial or HR spreadsheet.
XLSX upload validation: what to check
A robust upload handler validates more than the file name. Test that it accepts the MIME type application/vnd.openxmlformats-officedocument.spreadsheetml.sheet, checks that the content begins with the ZIP signature (the bytes PK, the same signature as a dummy ZIP file), and rejects a text file renamed to .xlsx.
Then test size boundaries. Set the unit to B and request one byte below, at and above your limit, for example 5242879, 5242880 and 5242881 bytes for a 5 MB limit. Because the extra size is a stored filler part, these files stay valid ZIP archives at every size.
Excel file size limits and worksheet limits
Excel worksheets hold at most 1,048,576 rows by 16,384 columns. Those are row and column limits, not file-size limits, and a workbook can be tens of megabytes without reaching them. This dummy workbook tests file size and file handling, so it does not exercise the row limit.
When you need many rows, generate a CSV instead: its Number of rows option goes up to 1,000,000, which fits under Excel’s row limit.
| Limit | Size | Notes |
|---|---|---|
| nginx client_max_body_size (default) | 1 MB 1,048,576 B | Requests with a larger body get HTTP 413. |
| PHP upload_max_filesize (default) | 2 MB 2,097,152 B | Also capped by post_max_size, so raise both. |
| AWS Lambda synchronous invocation payload | 6 MB 6,291,456 B | Applies to request and response. |
| Amazon API Gateway REST API payload | 10 MB 10,485,760 B | Hard quota for REST APIs. |
| Outlook default attachment limit (Exchange accounts) | 10 MB 10,485,760 B | Administrators can change it. |
| Outlook attachment limit (internet accounts) | 20 MB 20,971,520 B | Per Microsoft Outlook guidance. |
| Gmail message size limit | 25 MB 26,214,400 B | Attachments grow about a third when encoded, so a 20 MB file can already be too big. |
Dummy XLSX versus a real workbook
A production spreadsheet compresses well, so a 10 MB file may unzip to far more. The dummy workbook stores its filler uncompressed, so it is the size on disk that you asked for and has almost nothing to parse. That makes it a good probe for transport and storage limits, and a poor one for parser performance.
Excel file details
- Extension
- XLSX .xlsx
- MIME type
- application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
- Smallest size
- 4 KB
- Largest size
- 50 MB
- Contents
- Excel OpenXML workbook with one worksheet, a header row and two records; structure checked, not opened in Excel
Dummy Excel file FAQ
Will the dummy XLSX open in Excel?
It is an OpenXML package (a ZIP of XML parts) with a worksheet, the container format of every .xlsx file. We check its ZIP structure and workbook parts automatically, but not in every spreadsheet application, so open it in yours to confirm. Because the extra size is a stored filler part, the archive stays a valid ZIP at every size.
What is the largest dummy Excel file I can create?
From 4 KB up to 50 MB. The cap keeps browser memory use reasonable.
Is the file size exact?
Yes. Choose a size and unit and the downloaded workbook matches that byte count. For example, 5 MB is 5,242,880 bytes.
How many rows does the dummy Excel file have?
Two data rows and a header, at any size. The size comes from a filler part in the archive. For files with thousands of rows, use the dummy CSV generator.
What is the maximum number of rows in an Excel sheet?
Excel supports 1,048,576 rows and 16,384 columns per worksheet. Those limits are separate from file size.
Do you store my file?
No. It is built locally in your browser and never uploaded.