The limit that stops you is rarely the one you checked. Your provider allows 25 MB; the recipient's server may allow 10.
Pick the route by size
| Size | Route | Watch out for |
|---|---|---|
| Under 15 MB | Email attachment | Recipient limit may be lower |
| 15–100 MB | Cloud link (Drive, Dropbox, OneDrive) | Check sharing permissions |
| 100 MB – 2 GB | Cloud link or WeTransfer | Free tiers expire the link |
| Over 2 GB | Dedicated transfer or physical media | Upload time becomes the constraint |
| Recurring, same people | Shared folder | Set it up once, stop thinking about it |
The 15 MB figure is not the stated email limit — it is what survives it. Base64 encoding adds about 33%, so a 20 MB file travels as roughly 27 MB and bounces off a 25 MB ceiling. Aim for 70% of whatever the stated cap is.
Why zipping does almost nothing
ZIP compresses by finding repetition. PDFs, JPEGs, PNGs, MP4s and Office documents are all already compressed internally, and compressed data looks close to random — there is no repetition left to find.
Zipping a folder of photographs typically saves 0–2%. Zipping a PDF saves 0–5%. People try it because it is the obvious move and are surprised when 48 MB becomes 47 MB.
- Zipping is worth it for: many small files bundled into one, text and CSV files (which compress enormously), and getting past filters that block certain file types.
- Zipping is not worth it for: making a PDF, photo or video meaningfully smaller. Compress the content instead.
If you need a PDF to genuinely shrink, re-encode the images inside it. Compress PDF at 150 DPI typically removes 60–80% of a scanned document, which is two orders of magnitude more than ZIP will give you.
Reduce before you route
Before reaching for a transfer service, check whether the file needs to be that large. Very often it does not.
- Compress images before assembling. Phone photos are 3–6 MB each; at quality 0.75 they are typically 70% smaller with nothing visible lost.
- Send the part they asked for. A 200-page report where they wanted chapter 4 is a 200-page problem you invented. Split PDF extracts it in seconds.
- Check for an embedded background. A "text" document weighing 40 MB usually has a full-page image behind every page — see why is my PDF so big.
- Drop the resolution to the use. Screen reading does not need 300 DPI.
Sharing a link without oversharing
A cloud link solves the size problem and introduces an access one. The default on most services is more permissive than people assume.
- "Anyone with the link" means exactly that. Links get forwarded, pasted into tickets, and indexed if they ever appear on a public page.
- Prefer named recipients for anything confidential. It is one extra step and it makes access revocable per person.
- Set an expiry where the service allows it. Most sharing is for a week, not forever.
- Remember the link outlives the conversation. A file shared in 2026 is still reachable in 2031 unless someone removes it.
For handing a link to someone in the room, a QR code is faster than reading a URL aloud — the QR Code Generator makes one on your device without the link touching a third-party service.
What survives the trip
Different channels treat files differently, and some quietly damage them.
Email passes attachments through unchanged. This is its one real virtue at small sizes.
WhatsApp and Telegram re-compress images aggressively but leave documents alone. Sending a scan as a photo destroys it; sending the same scan as a PDF document preserves it exactly.
Slack and Teams store the original and generate previews from it, so the download is intact.
iMessage may downscale images depending on settings and connection.
The rule that avoids all of it: if fidelity matters, send it as a document or a link, never as an inline image.
Frequently asked questions
What is the largest file I can email?
Aim for under 15 MB regardless of the stated limit. Base64 encoding inflates attachments by about a third, so a 20 MB file travels as roughly 27 MB. The recipient's server may also cap lower than yours — corporate Exchange commonly stops at 10 MB — and you cannot see their limit.
Does zipping make files smaller?
Barely, for anything already compressed — PDFs, JPEGs, PNGs, videos and Office files all save 0-5%. ZIP finds repetition, and compressed data has none left. It is genuinely useful for bundling many files or compressing text and CSV, which shrink enormously.
Why did my email bounce when the file was under the limit?
Either encoding overhead pushed it over, or the receiving server has a lower cap than your provider. The bounce can arrive hours later because it happens at the recipient's end, not when you press send.
Is WhatsApp safe for sending documents?
For fidelity, yes — it accepts documents up to 100 MB and leaves them untouched. Attach as a document, not as an image: images are re-compressed aggressively, which destroys a scan. Whether it is appropriate for confidential material is a separate question.
Should I use a cloud link or an attachment?
Attachment under 15 MB, link above it. A link also lets you replace the file later without sending a second email, and lets you revoke access. The cost is that you have to think about sharing permissions, which default to more open than most people expect.
How do I make a PDF small enough to email?
Compress the images inside it rather than zipping the file. At 150 DPI and quality 0.75, a scanned document typically loses 60-80% of its size with nothing visible gone. If it is still too big, send the pages they actually asked for.