Compress PDF for Gmail
Reduce PDF size to pass Gmail's 25 MB attachment limit reliably — targets 10 MB to cover base64 overhead.
Send large PDFs through Gmail without rejection
Gmail imposes a 25 MB total attachment limit per email. The catch: email attachments are base64-encoded in transit, which adds approximately 33% to the actual payload. A 25 MB PDF file therefore becomes ~33 MB on the wire — exceeding Gmail's own limit, causing silent rejections where the email appears sent but the recipient never gets it. This tool targets 10 MB, so the on-wire payload stays around 13 MB — well inside Gmail's limit with room for message text and other small attachments.
Why Gmail's 25 MB limit is misleading
- Gmail measures the total RFC 2822 message size, not the raw file size
- MIME encoding adds ~33% overhead: a 20 MB PDF becomes 26.6 MB in the message
- The Gmail interface shows the file size, not the encoded size — creating false confidence
- Corporate recipients using Microsoft Exchange or Postfix may have even tighter limits (5–10 MB)
When to use Google Drive instead
If your PDF must stay above 10 MB (architectural drawings, high-res portfolios), use Google Drive: upload the file and share a link via Gmail. The recipient gets full quality without download friction, and you avoid size limits entirely. This tool is for when you must send the PDF as an attachment — not a link.
How to use this tool
- Upload your PDF.
- Click Compress — targets 10 MB.
- Download and attach to your Gmail email.
Frequently asked questions
Why does the tool target 10 MB if Gmail allows 25 MB?
Base64 encoding adds 33% in transit. A 19 MB PDF becomes 25.3 MB on the wire — over the limit. Targeting 10 MB keeps the encoded payload at ~13.3 MB, safely under 25 MB.
My recipient uses Outlook — is 10 MB still safe?
Outlook/Microsoft 365 allows 20 MB attachments. A 10 MB file encodes to ~13 MB on the wire, which is under Outlook's limit. For corporate Exchange servers with tighter caps, compress to 5 MB.
Can I attach multiple compressed PDFs in one Gmail?
Yes, but check their combined encoded size. Two 10 MB files become ~26 MB on the wire — slightly over Gmail's limit. Keep total attached PDFs under 18 MB raw for safety.
Gmail suggested using Google Drive — is that better?
For large files, yes — Drive avoids size limits entirely. But attachment delivery guarantees are stronger than link-based sharing for official correspondence.
Is my PDF uploaded to process?
No — compression runs in your browser. Your PDF is never sent to any server.