Why email has size limits
Email was designed for text, and attachments ride along inside the message. To travel safely between mail servers, a PDF is converted into plain characters using an encoding called Base64, which makes it roughly a third larger on the wire. Every server on the way, including the recipient’s, can refuse a message that crosses its limit. Some reject it outright, others bounce it back hours later.
Common limits
At the time of writing, Gmail accepts up to 25 MB of attachments per message and offers a Google Drive link above that. Outlook.com also allows 25 MB. Workplace mail systems set their own limits, which can be lower; some cap a whole message at 10 MB, so aim for about 7 MB when sending to one of those. Because you rarely know what the other side accepts, this page aims for 10 MB by default. For Gmail specifically, see the Gmail page.
How the compression works
The tool recompresses the photos and scanned images in your PDF. It starts at the Balanced setting and, if the file is still over the target, lowers image quality in a few passes until it fits. Text, fonts and links are left as they are, so a contract or invoice reads exactly like the original.
The finished file is never bigger than the one you started with. If the target cannot be reached, you get the smallest version the tool could make and a clear note saying so.
Good habits for emailing PDFs
- Send one clean file. Several scans merged into one document with Merge PDF are easier to handle than a stack of attachments.
- Remove what is not needed. Cover pages and blank backs add weight. Delete pages takes care of them.
- Think about the reader. A 10 MB attachment on a phone over mobile data is slow. When images do not matter much, compress to 2 MB instead.
Nothing leaves your device while you work, and there is no account or sign-up.
Frequently asked questions
What is the attachment limit for email?
It depends on the provider and on the organization. At the time of writing, Gmail and Outlook.com both allow 25 MB of attachments per message. Company mail servers often set their own limits, and the recipient’s limit matters as much as yours.
Why does this page aim for 10 MB instead of 25 MB?
Because you usually do not know the recipient’s limit. Attachments also grow by about a third when they are encoded for sending, and a smaller file arrives faster. 10 MB is a cautious target that clears most personal-mail limits. If you know the recipient’s workplace caps messages at 10 MB, aim for about 7 MB instead.
Can I pick an exact number?
Yes. Edit the Custom target field, or pick one of the preset sizes in the Target size menu.
Is it safe to compress a confidential attachment here?
Yes. The document is processed inside your browser and never uploaded. That makes it suitable for contracts, invoices and medical letters.