The limits
| Service | Attachment limit | Source |
|---|---|---|
| Gmail (personal account) | 25 MB | Gmail Help |
| Outlook.com | 25 MB, including message text | Microsoft Support |
| Google Workspace / Microsoft 365 (work accounts) | Set by your administrator | — |
Two details catch people out:
- Encoding overhead. Attachments are encoded for transport, which adds roughly a third to their size — Google’s Workspace documentation puts it at about 37%. A file that looks like 22 MB on disk can be over the limit in transit.
- The recipient’s limit matters too. Your provider may accept the message and theirs may reject it. Corporate mail servers are often stricter than 25 MB.
Practical target: keep a single attachment under about 15 MB, and under 10 MB if you are emailing a company or government address.
Fastest route
- Open the compressor — it runs in your browser, so a confidential PDF never gets uploaded anywhere.
- Start with medium. It is the right setting for anything that will be read on a screen.
- If the result is still too big, run it again on low. Scans and photos stay legible on screen; fine print and small table text are where low starts to hurt.
- Check the result before sending: zoom into the smallest text on the page.
If the PDF is mostly typed text and the browser says the file would get bigger, it is already compact — the size is probably coming from embedded fonts or a few large images. The desktop app (Ghostscript) handles that case without turning text into images.
When compression is the wrong tool
If a 200-page scanned contract is 300 MB, no setting will take it under 25 MB while keeping it readable. Share a link instead (Google Drive, OneDrive, Dropbox) — both Gmail and Outlook.com offer this automatically when an attachment is too large.
Not sure what is making your file large? Five common causes.