Before composing the email
Quick lookup before you waste 5 minutes writing the email and attaching — only to have it bounce because the file is 26 MB.
All tools
Email Attachment Size Checker
Check if your file will fit as an email attachment for Gmail, Outlook, iCloud, ProtonMail, and 8 other email providers.
- 100% local
- No signup
- Works offline once loaded
or
What this does
Find out which email providers will accept your file — before you hit send.
Different email providers cap attachments at different sizes: Gmail 25 MB, Outlook web 20 MB, iCloud Mail Drop 5 GB, ProtonMail 25 MB. Drop your file (or enter its size), see at a glance which providers it'll fit through and which will bounce it. No upload — runs locally.
How to check attachment fit
- 1
Drop a file or type a size
Either drag your file (we just read the size, not the contents) or type a size in MB. Both work.
- 2
See compatibility across 11 providers
Sorted by size limit ascending. Each provider shows fits/too-big with its current size cap.
- 3
If too big — try alternatives
Above 25 MB, the tool suggests sending a link via BulkShare / WeTransfer / Smash instead of attaching. One click to our send-large-files guide.
When this saves you time
Sending to mixed providers
If recipients are split across Gmail and old Outlook installs, the smallest cap wins. Check both before sending.
Knowing internal mail limits
Corporate IT often configures even lower caps (10-50 MB). Knowing the cap saves an awkward back-and-forth with the admin.
Phone email apps with their own quirks
Some mobile apps fail silently on attachments their underlying server would accept. Pre-check via web first.
Old Outlook still common in some industries
Legal, finance, government — old Outlook clients with 20 MB caps are still common. Worth knowing before sending privileged or time-sensitive material.
Email provider attachment caps (May 2026)
Sorted by size. Caps can change without notice — re-check if your file is on the boundary.
Outlook (web) — 20 MB
Best for: Default cap; smaller than Gmail surprisingly often
Gmail / Yahoo / AOL / Proton / Tutanota — 25 MB
Best for: Standard for most consumer email
Enterprise (typical) — 35 MB
Best for: Configured by IT, varies widely (10-50 MB common)
Fastmail — 50 MB
Best for: More generous than most
Outlook (Microsoft 365) — 100 MB
Best for: Higher with OneDrive auto-attach as a link
iCloud Mail Drop — 5 GB
Best for: Only for Apple-to-Apple recipients via iCloud
Email attachment tips
- 01
Email expands the file size by ~33%
Email encoding (MIME/base64) inflates attachments. A 19 MB file becomes ~25 MB on the wire. Stay 5 MB under the cap to be safe.
- 02
Send a link, not an attachment, for anything over 20 MB
Even if it fits the cap, large attachments slow recipient inboxes and risk getting flagged as suspicious. Just send a link.
- 03
ZIP doesn't help much
If your file is a photo/video/PDF (already compressed), ZIPing adds no real size reduction. Send the original, or send a link.
- 04
Corporate IT may scan and strip
Even within the size cap, corporate email gateways often strip executables, ZIPs, and macro-enabled documents. Test with a small ZIP first to know your sandbox.
More free tools for the handoff.
ZIP File Creator
Upload multiple files, create one ZIP archive, rename it, and download instantly.
Compression Toolkit
Compress real files in-browser with dedicated PDF, Docs, and Image subtools.
Client Delivery Email Generator
Generate a clean client-ready email with link, access steps, and support info.
PDF Compressor
Reduce PDF file size in-browser and download a smaller PDF quickly.
PDF Merge
Combine multiple PDFs into a single file. Drag, reorder, merge — fully in your browser.
PDF Split
Split a PDF into individual pages or custom page ranges. Browser-only, no upload.
Frequently asked
Gmail: 25MB. Outlook (web): 20MB. Outlook (Microsoft 365): 100MB. iCloud Mail Drop: 5GB (Apple recipients only). ProtonMail: 25MB. Yahoo: 25MB. AOL: 25MB. Most enterprise email systems: 10-50MB depending on admin config. The tool checks all of these.
Email was designed in the 1970s for text. Attachments were retrofitted later, and each provider sets its own limit based on infrastructure and abuse concerns. There's no universal standard — which is why this tool is useful.
Use a file transfer service instead of email attachment. BulkShare, WeTransfer, Smash, Filemail all handle files larger than email allows. The tool recommends specific services based on your file size.
Sometimes. ZIP compression helps for text/code (50-80% reduction) but barely helps for already-compressed files (JPG, MP4, PDF). The tool also suggests compression if it would bring your file under the threshold.
Usually yes for the same provider. But cross-provider: Gmail's 25MB applies to OUTGOING attachments. If you receive a 30MB attachment forwarded through your Gmail, it depends on the original sender's limits too.
Email encoding inflates attachments ~33% — a 20MB file becomes ~27MB on the wire, over Gmail's 25MB cap. Keep attachments under ~18MB real size, or send a link.
Yes — your provider may accept the send, but the recipient's server can still reject it. Corporate gateways are often stricter than Gmail. Links bypass both ends.
Upload it, email the link. The message is a few KB, lands in any inbox, and the recipient downloads at full speed — no bounce risk, and with BulkShare you see when they opened it.
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