Decompress GZ Files Online — Open .gz Without WinZip
A .gz file is a single file compressed with gzip. Unlike ZIP or TAR which can bundle multiple files, gzip is designed for compressing exactly one file — making it smaller for storage or transfer. When you see a file named access.log.gz or data.json.gz, that gz extension just means the original file was compressed.
FastZip decompresses .gz files directly in your browser. Drop in your .gz file and you'll get the original file back — whether that's a log file, database dump, JSON dataset, or anything else.
Common GZ file types you'll encounter:
- Server logs — Web servers (nginx, Apache) and application servers often gzip logs automatically before archiving them.
access.log.gz,error.log.2024-01-01.gz, etc. - Database dumps — MySQL and PostgreSQL dumps compressed with gzip:
backup.sql.gz - Data science files — CSV and JSON datasets compressed to save bandwidth:
dataset.csv.gz,embeddings.json.gz - Debian packages — Inside .deb packages, the data is often stored as
data.tar.gz - HTTP responses — Browsers receive gzip-compressed responses from web servers transparently, but if you're capturing network traffic you may encounter raw .gz responses
GZ vs GZIP vs GZip — These are all the same thing: different ways to refer to the GNU zip compression tool and format. The format is standardized in RFC 1952. FastZip uses the same underlying deflate algorithm as every other gzip implementation — the output is bit-for-bit identical to what gunzip on the command line would produce.
Format & Feature Reference
| Property | Details |
|---|---|
| Compression algorithm | DEFLATE (RFC 1951) |
| Files per archive | 1 (single file only) |
| Max file size (free) | 200 MB compressed |
| Checksum | CRC-32 of uncompressed data |
| Stores filename | Optional (in header) |
| Encryption | Not supported by gzip |
| Streaming decompress | Yes |
Viewing Log Files Compressed as .gz
System administrators frequently deal with rotated and gzip-compressed log files. If you've downloaded a *.log.gz file from a server for analysis and don't have gunzip handy, FastZip decompresses it to the original log file in seconds.
After decompressing, you can open the resulting .log or .txt file in any text editor. FastZip downloads the decompressed file directly to your Downloads folder with the .gz extension removed (so access.log.gz becomes access.log).
Decompressing SQL Database Backups (.sql.gz)
Many database backup tools and hosting control panels (cPanel, Plesk) compress SQL exports as .gz files. Before you can import a backup.sql.gz file into a local MySQL or PostgreSQL server, you need the uncompressed .sql file.
FastZip gives you that .sql file in one step, entirely in your browser. For SQL dumps, the decompressed file may be significantly larger than the .gz — a 50 MB .gz might expand to 500 MB or more of SQL. Make sure your browser has enough memory and your disk has enough space before decompressing very large database backups.
GZ Files in Data Science Workflows
Datasets on Kaggle, HuggingFace, and other data repositories are often distributed as compressed CSV or JSON. Python and R can read .gz files directly (pd.read_csv('data.csv.gz')), but if you need to inspect the file format or first rows without loading it into code, FastZip lets you decompress and preview in the browser.
FastZip downloads the decompressed file so you can then open it in Excel, a text editor, or any other tool for inspection.