Why Office files get so large
A .docx, .pptx or .xlsx file is really a zip archive with a different extension. Inside it sits your text, your formatting, and a folder holding every image you ever pasted in — stored at full original resolution.
Paste a photo straight from your phone into a slide and shrink it to fit the corner, and the file still contains the full 8-megapixel original. Do that across thirty slides and you have a 60MB presentation that displays nothing you could not have shown in 4MB.
What this tool changes
It opens the archive, finds the images, resizes and re-encodes any that are larger than needed, and puts the file back together. Your text, layout, fonts, formulas, animations and comments are untouched.
The result opens and edits normally in Word, PowerPoint, Excel, Google Docs and LibreOffice.
What to expect
- Photo-heavy presentations: often 80 to 90 percent smaller.
- Reports with charts and screenshots: typically 40 to 70 percent smaller.
- Text-only documents: almost no change, because there is nothing to compress. That is expected, not a failure.
Related things people need
The images inside your document are what make it large, so compressing them before you paste them in avoids the problem entirely. The image compressor does that, and converting HEIC photos to JPG first will save you trouble in Word and PowerPoint too.
To send several documents at once, bundle them into a ZIP, which can also split them to fit an email limit.
What is actually inside a Word or PowerPoint file
Since 2007, Office files have been ZIP archives with a different extension. Rename a .docx to .zip, open it, and you will find a folder structure containing XML files describing your text and formatting, and a media folder holding every image you ever pasted in.
Those images are stored exactly as they arrived. Paste a photograph straight from your phone into a slide, drag it small enough to sit in a corner, and the file still contains the full eight-megapixel original. The slide displays it at 400 pixels wide; the file carries all 4000.
This is why presentations balloon. Thirty slides with a photograph each can produce a 60MB file displaying perhaps 4MB worth of actual visible detail.
What this tool changes and what it leaves alone
It opens the archive, finds the images, resizes and re-encodes any larger than needed, and reseals the file. Everything else is untouched, byte for byte: your text, formatting, fonts, styles, tables, formulas, charts, animations, slide transitions, speaker notes, tracked changes and comments.
The result opens and edits normally in Word, PowerPoint, Excel, Google Docs, LibreOffice and Apple's iWork. It is the same document, with smaller pictures inside it.
Realistic expectations by document type
- Photo-heavy presentations — typically 80 to 90 percent smaller. This is the case the tool is really for.
- Reports with charts and screenshots — usually 40 to 70 percent. Screenshots are often stored as PNG and resize well.
- Documents with a logo and little else — a few percent at most. There is nothing substantial to work on.
- Pure text documents — essentially no change, which is expected rather than a failure.
- Spreadsheets — usually no change, since size there comes from data and formulas rather than pictures.
Avoiding the problem in the first place
If you regularly build presentations, compressing images before pasting them saves trouble later. A photograph resized to 1600 pixels looks identical on any projector and takes a tenth of the space.
PowerPoint and Word also have a built-in Compress Pictures option under the Picture Format tab, which does something similar. It is worth knowing about, though it applies its own presets rather than letting you choose, and it is easy to forget before sending.
One thing worth knowing: cropping an image inside Office does not remove the cropped-away parts from the file by default. They are merely hidden, and still occupy space. The Compress Pictures dialog has a checkbox to delete them permanently.
Questions
Will the document still be editable?
Yes. Only the embedded pictures are replaced. Everything else in the file is preserved exactly as it was.
Does it work with older .doc and .ppt files?
No. The older formats are not zip archives and cannot be processed this way. Open the file in Word or PowerPoint and save it as .docx or .pptx first.
Is my document uploaded anywhere?
No. Everything happens in your browser. Nothing is transmitted, which matters when documents contain client information, contracts or unpublished work.