Archives & ZIP
ZIP, TAR.GZ or GZIP - and when compression actually helps
Archives do two unrelated jobs - bundling many files into one, and compressing bytes. Understanding which job you actually need explains ninety percent of archive confusion, including the eternal mystery of the ZIP that is not smaller.
Key takeaways
- ZIP is the universal choice: built into Windows, macOS, Android and iOS - no recipient will be confused.
- TAR.GZ compresses all files as one stream, which wins on many similar text files - the Linux world's default.
- GZIP compresses exactly one file; it is a compressor, not a bundler.
- Compression only shrinks uncompressed data: text, CSV, logs, BMP. Photos, videos and PDFs are already compressed and barely budge.
Three formats, two jobs
ZIP compresses every file independently, which allows extracting a single file quickly but wastes potential when many files resemble each other. TAR.GZ concatenates everything first and compresses the result as one stream - similar files share their redundancy, so a folder of 500 log files often lands dramatically smaller as .tar.gz than as .zip.
| Format | Bundles files | Compression | Best for |
|---|---|---|---|
| ZIP | yes | per file (Deflate) | sending anything to anyone |
| TAR | yes | none | preserving Unix permissions, pipeline use |
| TAR.GZ | yes | one stream over all files | source code, log collections, backups |
| GZIP (.gz) | no - single file | one stream | compressing one big text/CSV/log file |
Why your ZIP full of photos is not smaller
Compression removes statistical redundancy. JPG photos, MP4 videos, MP3 audio and most PDFs have already been through a specialized compressor - the redundancy is gone. Running Deflate over them again finds nearly nothing: typical savings are 1-5%, sometimes the archive is even a hair larger than the sum of its parts.
Zipping such files is still useful - as packaging. One attachment instead of thirty, folder structure preserved, nothing forgotten. Just do not expect the megabytes to drop. If they must drop, compress the media itself first - image and video compression save 70-90% where ZIP saves 3%.
What compresses brilliantly
- Text, source code, HTML, JSON, XML: routinely 70-90% smaller.
- CSV exports and database dumps: often 80-95% smaller - repeated field names and values are compression gold.
- Log files: the most compressible data in computing; 95%+ is normal.
- Uncompressed images (BMP, uncompressed TIFF): huge wins - though converting to PNG or JPG is usually smarter than archiving.
Archives vs. email filters
Corporate mail servers treat archives with suspicion: many block encrypted ZIPs outright because scanners cannot look inside, and some quarantine any archive containing executables, scripts or Office macros. If your perfectly innocent ZIP never arrives, the recipient's filter is the first suspect - resend the files individually or via a link.
Password-protected ZIPs also deserve honesty: the classic ZipCrypto scheme is weak and mainly signals intent; treat it as a courtesy seal, not as encryption for genuinely confidential data.
Picking the right format for the recipient
Sending to a person: ZIP, always. Every mainstream operating system opens it with a double click or tap; nobody needs to install anything. Sending to a Linux server, a build pipeline or a developer: TAR.GZ preserves permissions and symlinks and is the ecosystem's native tongue. Compressing one giant CSV or log for storage: GZIP, done.
The FileSizeFix archive tools create ZIP, TAR, TAR.GZ and GZIP directly in your browser - files are bundled and compressed locally, nothing is uploaded. RAR and 7Z are deliberately absent: browsers ship no trustworthy encoder for them, and honest tools beat pretend ones.
Frequently asked questions
Why is my ZIP file barely smaller than the original files?
Because the contents - photos, videos, PDFs - are already compressed formats. ZIP cannot compress them further; it only bundles them. Compress the media files themselves to actually save space.
What is the difference between ZIP and TAR.GZ?
ZIP compresses each file separately; TAR.GZ bundles everything first and compresses it as one stream. TAR.GZ typically wins on many similar files, while ZIP allows fast access to individual files and has the broadest support.
Can iPhones and Android phones open ZIP files?
Yes - both platforms open ZIP archives with a tap, no extra app required. That built-in support is exactly why ZIP is the safest choice for sending.
Why does FileSizeFix not create RAR or 7Z archives?
Browsers provide no reliable built-in encoder for those formats. Rather than upload your files to a server or ship a poor emulation, the tools stick to formats they can build honestly on your device: ZIP, TAR, TAR.GZ and GZIP.