How to Reduce Email Attachment Size

Your email won’t send because the attachment is too big. Or the recipient says it bounced. Or the corporate firewall stripped your file. Email attachments have practical limits — typically ~25 MB before things break.

Here’s how to fit attachments under the limit for every file type.

The actual limits

• Gmail: 25 MB
• Outlook (Microsoft 365): 35 MB default, configurable
• Outlook.com (personal): 25 MB
• Yahoo Mail: 25 MB
• iCloud Mail: 20 MB
• ProtonMail: 25 MB

Practical limit accounting for MIME encoding overhead: ~18 MB. Files over this size are at risk.

Strategy 1: Compress by file type

Images

Phone photos / camera images: typically 3-10 MB each.

• Use Image Compressor at quality 0.85: 60-80% smaller
• Use Image Resizer if dimensions are larger than needed
• A 5 MB iPhone photo typically compresses to 500 KB

Multiple images: bundle into a PDF (smaller than separate files):

• JPG to PDF for combining
• PDF Compressor for further shrinkage

PDFs

• PDF Compressor at Medium: typically 40-60% reduction
• For very heavy compression: High or Extreme settings — 70-90% smaller
• Multi-page PDFs can also be split with PDF Splitter and sent in parts

Videos

Hardest to compress. Most “free” browser tools don’t handle this well.

• HandBrake (desktop, free): typically 70-90% reduction
• A 100 MB iPhone 4K video → 20-40 MB at 1080p with HandBrake
• See our Compress Video guide

Audio

• WAV → MP3 with WAV to MP3: ~10× smaller
• FLAC → MP3 with FLAC to MP3: ~5× smaller
• A 60 MB WAV → 6 MB MP3 at 192 kbps

Documents (Word, Excel, PowerPoint)

These are typically small. If yours is huge, it usually contains:

• High-resolution embedded images: compress them in the source document
• Excessive embedded objects: simplify before attaching
• Convert to PDF: usually a smaller representation than the original Office format

Strategy 2: Switch to a link

When compression isn’t enough, share via link instead:

WeTransfer (free): up to 2 GB, 7-day expiry, sends recipient an email with download link. No signup needed.

Smash (free): no size limit on free tier, longer retention.

Google Drive / Dropbox / iCloud: share existing files; recipient clicks to download. Free up to your storage limit.

Send Anywhere: peer-to-peer transfer, no upload to a server (if both parties online simultaneously).

For files too big to compress under 18 MB, link sharing is the answer. For sensitive content: use a service with end-to-end encryption (Tresorit Send) or password-protect a ZIP before uploading.

Strategy 3: ZIP the file (mixed effectiveness)

ZIP works well for:

• Text files, documents, code (50-70% reduction)
• Folder structures with mixed content
• Anything not already compressed

ZIP doesn’t help much for:

• JPGs, PNGs, MP4s, PDFs (already compressed; ZIP adds 0-5%)
• Already-compressed archives

For some file types, ZIPping is essentially a no-op compression-wise — but it does bundle multiple files into one for easier sending.

Strategy 4: Send multiple emails

For files that can be split logically:

• Multi-page PDFs: PDF Splitter into chunks
• Multiple photos: send in batches
• Long audio: Audio Trimmer to split

The recipient has to manage multiple emails which is awkward. Usually links are better than splitting.

Workflow examples

“This iPhone photo won’t send”:

1. Open Photos → Edit → Done (re-saves in iOS, sometimes reduces size)
2. Or: Image Compressor at quality 0.85
3. Email the compressed version

“This PDF report is 30 MB and Gmail rejects it”:

1. PDF Compressor at Medium → typically 15 MB
2. Still too big? Try High → ~10 MB
3. Or split with PDF Splitter into 2-3 parts

“I need to send a long video”:

1. HandBrake compression → 1080p30 preset
2. If still too big → WeTransfer or YouTube unlisted upload

“Multiple files together”:

1. Bundle into a ZIP
2. If too big: compress each first, then ZIP
3. If still too big: WeTransfer

Compression quality vs size trade-offs

Higher compression = smaller files but visible quality loss:

• For preview-quality: maximum compression often acceptable
• For working copies: medium compression preserves quality
• For archival or print: minimal compression; use link sharing instead

For most “send me this attachment” use cases, quality 0.80-0.85 compression is invisible to the recipient.

When sensitive content is involved

For confidential attachments:

• Avoid public file-sharing services (WeTransfer, generic services)
• Use end-to-end encrypted services (Tresorit Send, ProtonMail attachments)
• Password-protect ZIP files (send password through a different channel)
• Consider whether email is the right channel at all — encrypted messaging or secure portals are better for highly sensitive content

TL;DR

• Email limit: 18 MB practical (25 MB nominal)
• Compress images: Image Compressor at quality 0.85
• Compress PDFs: PDF Compressor at Medium
• Compress audio: WAV to MP3, FLAC to MP3
• Compress video: HandBrake desktop tool
• Switch to link: WeTransfer (free, 2 GB), Google Drive, Dropbox
• ZIP: bundles files; modest compression except on already-compressed formats
• For sensitive content: encrypted services or password-protected ZIPs