Compress CSV/XLSX
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Supported formats: .csv,.xlsx,.xls,.xlsm,.xlsb,.tsv
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About Compress CSV/XLSX
Compress CSV and XLSX files online for free, losslessly, with no upload. Shrink spreadsheets past email attachment limits and upload caps in seconds, straight in your browser.
The file is passed through a lossless DEFLATE/ZIP compression pass entirely in your browser, so the byte-for-byte content of your CSV or XLSX is preserved and just packed into a smaller archive.
No rows, columns, formulas, or formatting are touched, only the container size shrinks, which is what matters when you are up against an email attachment limit or an upload quota.
CSV files usually compress hardest, often 70-95% smaller, because repeated delimiters, commas, and similar text values give DEFLATE a lot to work with. XLSX files are already zip-based internally, so gains are typically smaller but still meaningful, especially on files with a lot of repeated string data or unused formatting bloat.
Because the whole process runs client-side, the file never leaves your machine, there is no upload wait, no server-side processing queue, and no privacy tradeoff for compressing something that might contain customer or financial data.
Category: Transformation & LogicCommon Use Cases
- Shrinking a 40MB export below a 25MB Gmail or Outlook attachment limit without splitting it into parts
- Packing several XLSX reports into one ZIP before uploading to a portal with a strict file size cap
- Reducing storage footprint for CSV exports you need to keep for compliance but rarely open
- Getting a large customer or transaction export small enough to attach directly to a support ticket
- Compressing a nightly database export before archiving it to cold storage or a backup drive
Key Features
- Lossless DEFLATE/ZIP compression of CSV and XLSX files, byte-for-byte data preserved
- No changes to underlying rows, columns, formulas, or formatting
- Runs fully client-side, files never uploaded to a server
- Works on files well beyond typical email attachment limits
- No sign-up, no install, no rate limit for casual use
The Compress CSV/XLSX tool is compatible with: Gmail, Outlook, SharePoint, Any ZIP-compatible upload portal.
Convert with CSV to XLSX or CSV to JSON first to get the file format you need, then compress the result here if it is still too large to email or upload. If you have many files to shrink at once, run them through Batch Processor first and compress the combined output.
Frequently Asked Questions
Yes, it reduces file size by zipping either format, and you can mix both in a batch.
No, it only reduces file size, the underlying data, formulas, and formatting are unchanged, this is lossless compression, not data reduction.
It depends on the content. Plain CSV with repetitive text often shrinks 70-95%. XLSX files are already partially compressed internally, so the gain is usually more modest but still enough to clear common attachment limits.
No. Everything runs locally in your browser using client-side compression, the file never leaves your device.
You get a standard .zip archive, extract it first and the CSV or XLSX inside opens exactly as it did before compression.
Yes, that's the main use case, compress it here first, then attach the resulting ZIP, which is often small enough to clear a 25MB or similar limit.
The tool is built to handle large exports directly in the browser; very large files depend on your device's available memory rather than a hard-coded cap.
A quick fix for anyone who has hit an attachment size limit while sending a spreadsheet, no desktop zip utility or IT ticket required.
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