How to make a ZIP file, and when zipping is pointless
Select the files, add them to a ZIP tool, and download the single .zip that comes out. A ZIP is one file that holds many, and it compresses them on the way in. Documents, spreadsheets and text shrink a lot. JPGs, MP4s and PDFs are already compressed, so zipping them mainly makes them convenient, not smaller.
A ZIP file does two jobs at once, and confusing them is why people are disappointed by it. First, it is a container: many files and folders wrapped into one file, with a small index at the end recording what is inside and where each piece starts. Second, it compresses each of those files as it packs them. The container part always works. The compression part depends entirely on what you put in.
What actually shrinks, and what does not
Compression works by finding repetition. A text file that says the same words over and over compresses beautifully. A file that has already been compressed has had its repetition removed, so there is nothing left to find. Squeezing it again gains you almost nothing, and occasionally the archive is a few kilobytes larger than the original because of the bookkeeping.
| What you zip | Comes out at roughly | Why |
|---|---|---|
| Plain text, CSV, log files | 10 to 25 MB | Enormously repetitive. The best case there is |
| Word and Excel files | 60 to 90 MB | Modern .docx and .xlsx are already zipped internally. Older .doc and .xls shrink much more |
| Uncompressed BMP or TIFF images | 30 to 60 MB | Large flat areas of the same colour compress well |
| JPG, PNG, GIF photographs | 95 to 100 MB | Already compressed. Essentially no gain |
| PDF files | 90 to 100 MB | Images and streams inside a PDF are already compressed |
| MP4, MP3, MOV media | 99 to 100 MB | Nothing to win. Zip these only to bundle them together |
So the honest summary: if you are zipping a folder of holiday photos hoping it will fit under an email limit, it will not. Zipping is still the right move, because it turns 40 attachments into 1, but you need to compress the images themselves if size is the actual problem.
Making a ZIP, step by step
- Gather the files firstPut everything in one folder and give it the name you want the recipient to see, such as
Invoices-2026-Q1. The folder name becomes the archive name and the folder people unpack it into, so it is worth thirty seconds of thought. - Open the ZIP toolGo to create ZIP and drop the files or the whole folder in. Everything is packed inside your browser tab. No file is uploaded, no account is required, and no quota is consumed however many archives you build.
- Check the listConfirm the file count and the total size before packing. This is the moment to notice that you dragged in a
.DS_Store, a duplicate, or last year's version by mistake. - Pack and watch the numbersThe tool reports the size before and after. If the two are nearly identical, that is expected for photos, video and PDFs, and it does not mean anything went wrong.
- Download and test itOpen the finished .zip once yourself before you send it. Ten seconds of checking prevents the message that begins "this file will not open".
Pack any set of files into one ZIP archive, entirely in your browser. Nothing is uploaded.
Create ZIP →The real reason to zip: one attachment instead of forty
Most email clients, ticketing systems, upload forms and shared drives are far happier with one file than with dozens. Zipping also preserves the folder structure, which plain attachments cannot. If your work is organised as Project/Photos/, Project/Drafts/ and Project/Final/, a ZIP arrives with that arrangement intact; attaching 40 loose files arrives as 40 loose files and the recipient has to guess.
- Sending a batch of documents to an accountant, a solicitor or a landlord, where the order and grouping matter.
- Handing over a project with its folders, so nobody has to reconstruct the structure at the other end.
- Getting past attachment count limits, which some corporate mail systems set as low as ten files.
- Archiving something you are finished with, so a hundred small files become one item in your backup.
- Protecting the file names, since some upload forms rename or lowercase files, but leave the contents of a ZIP alone.
What a ZIP does not do
A plain ZIP is not private. Anyone who has the file can list what is inside and open every item, and the file names are readable even before extraction. Zipping a folder of bank statements protects nothing at all. If a document genuinely needs protecting, put a password on the PDF itself rather than trusting the wrapper around it.
It also does not deduplicate across files in any useful way, it does not repair anything, and it does not make a corrupt file readable. And it does not speed up an upload of already-compressed material: 100 MB of video takes the same time to send whether it is bare or in an archive.
Doing it without a tool
Both desktop systems can make a ZIP with no software at all. On Windows, select the files, right-click, then Send to, then Compressed (zipped) folder. On macOS, select them, right-click, then Compress, which produces Archive.zip if you selected several items, or Name.zip if you selected one folder. From a terminal:
# macOS or Linux: zip a folder and everything in it zip -r invoices-2026-q1.zip invoices-2026-q1/ # Leave macOS metadata out of the archive zip -r -X clean.zip myfolder/ # Windows PowerShell Compress-Archive -Path .\invoices-2026-q1\* -DestinationPath invoices-2026-q1.zip
On macOS, right-click compression quietly adds a __MACOSX folder and .DS_Store files to the archive. They are harmless but they look untidy to a Windows recipient, who sees them as mystery extra items. A browser ZIP tool or the -X flag above leaves them out.
ZIP or a single PDF?
If the recipient is going to read your files in order, a PDF is usually better than a ZIP. They open one document and scroll, instead of extracting an archive and opening eight files one at a time. Scans, receipts and photographed paperwork are the obvious cases: turn the images into one PDF and send that. Use a ZIP when the files are genuinely separate things, when they are not all documents, or when the folder structure carries meaning. When someone sends you one, opening a ZIP file covers the other half of the job.
Frequently asked questions
How do I make a ZIP file?
Select the files, add them to a ZIP tool or right-click and choose Compress on macOS, or Send to, Compressed folder on Windows. You get one .zip file holding everything, with the folder structure preserved.
Does zipping make photos smaller?
Almost never. JPG and PNG are already compressed, so a ZIP of 100 MB of photos comes out at 95 to 100 MB. Zip them to send one attachment instead of forty, and compress the images themselves if you need the size down.
What kind of files shrink the most when zipped?
Plain text, CSV and log files, which are highly repetitive and can drop to 10 to 25 percent of their original size. Older Word and Excel formats also shrink well. Anything already compressed barely moves.
Is a ZIP file secure?
A plain ZIP is not. Anyone with the file can list and open everything inside, and the file names are visible before extraction. For genuine protection, encrypt or password-protect the document itself rather than relying on the archive.
Can I email a ZIP file?
Usually yes, though some corporate mail filters block or quarantine ZIP attachments because malware has been distributed that way. If your archive bounces, put it in a shared drive and send the link instead.