or click to choose. Notebook table of contents files (.onetoc2) work too.
Add a OneNote file to compress it. You’ll see the real savings, how much unused space is inside, and any pictures or attachments you can save separately.
Compressed entirely in your browser. Your notes are never uploaded, and attachments inside them are never opened.
This OneNote compressor packs .one sections, .onepkg notebook packages and .onetoc2 files into a standard ZIP or GZIP file and shows you honestly how much smaller they got. It also looks inside each file: how much space is unused, which pictures and attachments are stored in it, and what a notebook package contains. You can save the pictures and attachments, or unpack a .onepkg into its sections, without OneNote. Everything runs in your browser and your notes are never uploaded.
How to compress a OneNote file
- Drop one or more
.oneor.onepkgfiles onto the left box, or click it to choose them. - Pick ZIP or GZIP. ZIP opens on every computer and phone without extra software.
- Each file is compressed and checked right away. Results shows the real savings and why.
- Open Inside the file to see unused space, pictures and attachments, or the sections in a package.
- Click Download. Several files go into one ZIP, or one .tar.gz if you picked GZIP.
To open the notes again, unzip the download and open the .one file in OneNote. The unzipped file is identical to your original.
OneNote file types
| File | What it is | Typical ZIP savings |
|---|---|---|
.one | One section of a notebook, with all of its pages, pictures, ink and attachments | 30–70% for typed notes, less with many pictures |
.onepkg | A whole notebook exported as a single file. It’s a Microsoft Cabinet archive, so it’s already compressed. | 0–3% |
.onetoc2 | The notebook’s table of contents, which lists its sections | Small file, compresses well |
Why some OneNote files barely shrink
OneNote stores pictures, screenshots and file printouts in formats that are already compressed, like PNG and JPEG. Attached Word, Excel and PowerPoint files are ZIP files on the inside. A section full of screenshots may only get 5–10% smaller. Typed notes, tables and page structure compress well. The Inside the file tab shows how much of each file is pictures and attachments, so you can see why.
Sections also collect unused space as you edit. OneNote for Windows can remove it: go to File → Options → Save & Backup and click Optimize All Files Now. This tool shows how much unused space each section has, so you know whether that’s worth doing first.
Save pictures and attachments, or unpack a .onepkg
- Pictures and attachments: the tool finds every file stored inside a section, such as pictures, PDF and Office attachments, printouts and audio recordings, and lets you save them one by one or all at once. OneNote doesn’t store their original names next to the data, so they’re numbered.
- Unpack a .onepkg: a notebook package can normally only be opened by OneNote for Windows. Unpack sections turns it into a ZIP of ordinary
.onefiles you can open in any version of OneNote, or keep as a backup. - OneDrive format: sections downloaded from OneDrive or SharePoint use a different layout. The tool can still find their pictures, but not other attachments.
Is it safe?
Yes. Your file is only read, never changed, and nothing is uploaded. After compressing, the tool unpacks the result and checks that it matches the original exactly before you can download it. Attachments are never opened here. OneNote files have been used to send malware by email, so scan attachments from notebooks you didn’t make before you open them.
Frequently asked questions
Can I open the compressed file in OneNote?
Not directly. Unzip it first, then open the .one file. Windows, macOS, iOS and Android can all open ZIP files without extra software. For .gz files on Windows, use 7-Zip.
Can this make the section smaller inside OneNote?
No browser tool can safely rewrite a OneNote section. To shrink it inside OneNote, use Optimize All Files Now, delete old page versions in the History tab, and remove large printouts or attachments you no longer need.
Why did my .onepkg only shrink 1%?
A .onepkg is already compressed. Zipping it mostly helps with sending it through apps that block unfamiliar file types.
Is there a size limit?
The ZIP has to stay under 4 GB. Files over 1 GB are compressed in full, but their pictures and attachments aren’t listed.
What is the difference between ZIP and GZIP here?
Both use the same compression, so the size is nearly identical. ZIP opens anywhere and holds several files. GZIP holds one file, and is common on Linux and for backups.