Open a .csv.gz file (no extracting needed)
Data warehouses love shipping compressed CSVs: BigQuery exports, S3 data drops, log archives and API bulk downloads all arrive as .csv.gz because it typically cuts transfer size by 80–90%. Then you’re stuck with a file Windows won’t open, double-extension confusion (“is it a CSV? a gz? both?”), and advice to install command-line tools just to peek inside. Skip all of it: drop the .csv.gz here and it’s decompressed and displayed in one step — in your browser, using the browser’s own decompression engine.
The decompressed data never leaves your machine either — which matters, because compressed exports are usually exactly the kind of bulk customer or financial data you least want on a random website’s server.
Drop a CSV, TSV or Excel file here
.csv · .tsv · .txt · .csv.gz · .xlsx — files up to 4 GB open here, in your browser. Nothing is uploaded; the file is read in place on your device.
Filters combine with AND. Use the search box for a quick any-column match. Regex filters use JavaScript syntax.
Untick to hide a column (hidden columns are left out of exports). Type to rename — renames apply to exports too.
Exports include your filters, sort, edits and cleanups. Hidden columns are left out; renamed headers apply. The file is generated on your device — nothing is sent anywhere.
How it works
- Drop the .csv.gz (or .tsv.gz) file — no need to extract it first.
- It’s decompressed in the browser and indexed like any CSV.
- View, filter, clean and profile as usual.
- Export plain CSV (or Excel/JSON) — or split it into parts if the decompressed file is huge.
What a .csv.gz actually is
It’s a normal CSV run through gzip compression — one file, two extensions, each meaning one layer. CSV compresses spectacularly well because it’s repetitive text: the same headers, quoted patterns and category values over and over. A 500 MB export often ships as a 40 MB .gz. That’s why every serious data platform compresses by default — and why the decompressed size, not the download size, is what determines whether a tool can open it.
This viewer decompresses with the browser’s native DecompressionStream (the same gzip engine the browser uses for web traffic), so there’s no library download and it works offline. Budget for the decompressed size in memory: a 1 GB-decompressed file is the practical ceiling here.
Good to know
- Only gzip (.gz) is supported — .zip archives are a different container; extract those first (or if it’s an .xlsx, drop it directly).
- The 4 GB / 1 GB-decompressed limits are about your machine’s memory, not the format — split giant exports at the source when you can.
- Modern browsers only: the built-in decompression API has shipped in Chromium-based browsers since 2020 and in all three engines since 2023 — a genuinely old browser will say so rather than fail silently.
Frequently asked questions
Why won’t Windows open my .csv.gz?
Windows has no built-in gzip handler for double extensions — it sees an unknown .gz file. The usual fixes are installing 7-Zip or using WSL; this page is the no-install alternative: the browser decompresses it directly.
Where do .csv.gz files come from?
Bulk data exports, mostly: BigQuery and Redshift dumps, S3 data feeds, analytics platform exports, server log rotations. Compression cuts storage and transfer cost enormously for repetitive text like CSV, so platforms enable it by default.
Is the file decompressed on a server?
No — decompression runs in your browser via its built-in DecompressionStream API. Nothing is transmitted; you can watch the (empty) Network tab while it works.