One of the most common Excel cleanup tasks is surprisingly simple:
Remove all blank rows at the bottom of a worksheet.
It sounds trivial until you need to process dozens of large spreadsheets without uploading them to a server.
I recently built an online tool for exactly this task, and it turned out to be a perfect use case for WebAssembly.
remove empty rows in Excel (online with WebAssembly)
Why WebAssembly?
Instead of reimplementing Excel parsing in JavaScript, I reused the excellent excelize library written in Go.
By compiling it to WebAssembly, I can run the same Excel processing engine directly inside the browser.
The advantages are obvious:
🚀 Native-like performance
🔒 Files never leave the user's computer
📦 Reuse a mature Go library instead of maintaining another implementation
💻 Works on Windows, macOS and Linux without installation
Processing Real Excel Files
The tool loads standard Excel workbooks (.xlsx) and removes unnecessary blank rows at the bottom while preserving the workbook structure.
Because the processing happens locally, there is:
No file upload
No waiting for a server
No privacy concerns
For many users, that's much more important than shaving a few milliseconds off execution time.
Is a 4 MB WASM File Too Large?
This is a question I asked myself before building it.
The compiled excelize WebAssembly module is around 4 MB after gzip compression.
While that sounds large compared to typical JavaScript bundles, it's actually acceptable for an application that performs heavy document processing.
The module is downloaded only once and then cached by the browser.
Considering it replaces a backend service and processes Excel files entirely offline, the trade-off is well worth it.
Why Go + excelize?
There are several JavaScript libraries for reading Excel files.
However, excelize has been battle-tested for years and supports a large portion of the XLSX specification.
Instead of reinventing complex spreadsheet logic in JavaScript, compiling the existing Go implementation to WebAssembly lets me reuse reliable production code.
It's one of those situations where WebAssembly really shines.
Try It Yourself
If you often receive Excel files with hundreds (or thousands) of unnecessary blank rows at the bottom, you can try the tool here:
👉 Remove Blank Rows in Excel (Online)
No installation.
No uploads.
Everything runs directly in your browser.
Tech Stack
Go
excelize
WebAssembly (WASM)
Runs completely in the browser
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