Gmail Attachment Size Limit: 25MB, and Why a 20MB File Can Still Fail
Gmail, Outlook.com and Yahoo cap messages at 25MB, but encoding makes files larger in transit. What really fits, what happens above it, and how to shrink each file.
Updated September 15, 20266 min read
A personal Gmail account lets you send up to 25MB of attachments in one message, and anything larger is swapped for a Google Drive link automatically. Outlook.com and Yahoo Mail also stop at 25MB at the time of writing. The catch is that the file on your disk is not what travels: email encodes attachments as text, which makes them a third or more larger on the way, and Microsoft's and Google's own business documentation both describe limits measured after that encoding. That is how a 20MB file can fail a 25MB limit — and the fix is either a smaller file or a link.
The limits, at the time of writing
| Service | Limit | What it covers | When the file is too big |
|---|---|---|---|
| Gmail, personal account | 25MB | All attachments in the message together | Gmail replaces them with a Google Drive link |
| Gmail, work or school | Set by your administrator | Sending and receiving are set separately | The same Drive link |
| Outlook.com | 25MB | The whole email: text and attachments | Share from OneDrive; linked files up to 2GB |
| Outlook desktop app with Outlook.com, Gmail or another internet account | 20MB | The attachment plus the email | Share a cloud link instead |
| Microsoft 365 business mailbox | 35MB to send, 36MB to receive by default | The whole message; admins can set 1–150MB | OneDrive attachments up to 2GB |
| Yahoo Mail | 25MB | All attachments, incoming and outgoing | Share a cloud link instead |
Sources: Google's Gmail attachments help page, Microsoft's Exchange Online limits and the Outlook and Yahoo help centres. These numbers change on the providers' schedule, not ours, so treat them as a snapshot.
Receiving is where people get caught. Google's help page for personal accounts gives only the 25MB sending figure; its Workspace documentation gives a receiving limit of 50MB, or 70MB on Enterprise Plus, measured after encoding. What matters in practice is that a message has to pass every limit on its route — yours, the recipient's, and their company's mail server, which may be set far lower than any of the figures above. The smallest one decides, and a message it rejects comes back to you as a bounce.
Why a 20MB file can fail a 25MB limit
Email was built to carry text. To send a PDF or a video, your mail app converts it with base64 encoding, which represents every 3 bytes of the file as 4 text characters — a 33% increase before anything else is added. Line breaks and message headers add a little more; Google's Workspace documentation puts the total at about 37%.
So a 20MB video becomes roughly 27MB once encoded. Against a 25MB limit measured on the encoded message, the real room for files is about 18MB. Microsoft states this outright for business mail: messages leaving its data centres grow by 33%, so Outlook on the web restricts what you can send to 25% less than the configured limit — a 100MB setting lets you send 75MB.
What happens above the limit
Gmail does not refuse an oversized attachment; it uploads it to your Google Drive and puts a link in the email instead. Outlook.com offers the same with OneDrive, and Microsoft notes that OneDrive links do not count towards the email size limit, with linked files allowed up to 2GB.
A link is often the better answer: there is no size ceiling worth worrying about, and you can withdraw access later, which you cannot do with an attachment. But some recipients genuinely need a file in their inbox — an application portal that only accepts attachments, a colleague who works offline, an archive that stores messages. For those, the only answer is a smaller file.
How to shrink each type of attachment
| Attachment | Where the size is | What to do |
|---|---|---|
| Video | Resolution and bitrate | Set a size in MB in the video compressor |
| Scanned or photo-heavy PDF | The page pictures | Compress the PDF in Balanced or Strong |
| Photos | Megapixels | Set a KB target in the image compressor |
| PowerPoint deck | Pictures, unused layouts, editing history | Run it through the PowerPoint compressor |
| Word document | Pasted photos | Run it through the Word compressor |
Video is the usual culprit. The compressor's Size in MB mode takes a number — type 18 — and solves for a bitrate that lands under it; if the result looks soft, lower the resolution to 720p rather than raising the target. The free plan takes one video up to 100MB and five minutes, at up to 1080p; Pro adds batches and 4K. For codecs and resolution in more depth, see making a video smaller for WhatsApp and email.
PDFs are only large when they carry pictures. Strong recompresses those at 96 DPI and leaves text, links and form fields exactly as they were. Free handles one PDF up to 25MB and 100 pages; larger files need Pro. Compressing a PDF without wrecking the text explains which kind of PDF shrinks and which does not.
PowerPoint and Word files are packages of text and pictures, and nearly all the weight is pictures stored far larger than they are shown. Both compressors resize them, merge duplicates and drop media nothing uses; the PowerPoint one also removes unused slide layouts and co-authoring history. Free takes one deck up to 100MB or one document up to 50MB, with pictures capped at 1920 pixels and High quality; Pro lifts those caps and adds WebP pictures for recent Office versions.
What rarely helps is zipping. PDFs, videos, photos and Office files are already compressed internally, so a ZIP of them is usually barely smaller than the files themselves.
Type the size you need and the compressor aims under it. It all runs on your device, not our servers.
Compress a video to a size in MBSending files that are genuinely large
Some files should not be emailed at all: a ten-minute video squeezed into 18MB looks exactly like it was. Past that point, use the link your mail service already offers, or split the job. A long PDF can go in parts — the PDF splitter packs pages into as many files as it takes to stay under a size you set, such as 18MB each, one per email.
On a Microsoft 365 business account, the 35MB default can be raised by an administrator up to 150MB. That ceiling counts the encoded message, so the largest attachment it actually lets through is about 112MB. If you regularly send large files to clients, that is a conversation with your IT team rather than something to fight message by message.
Frequently asked questions
What is the Gmail attachment size limit?
25MB of attachments per message on a personal account, at the time of writing. Above that, Gmail uploads the files to Google Drive and sends a link instead. On work and school accounts, the administrator sets the sending and receiving limits.
What is the Gmail attachment size limit for receiving?
Google's personal-account help page states only the 25MB sending limit. Its Workspace documentation gives a receiving limit of 50MB, or 70MB on Enterprise Plus, measured after encoding. In practice the sender's service and any server in between must also accept the message, so the smallest limit on the route decides.
Why does my 20MB file fail a 25MB limit?
Attachments are encoded as text for sending, which makes them about a third larger — roughly 27MB for a 20MB file — and several attachments add up because the limit is per message. If the recipient's server measures the encoded size or has a lower limit, it bounces. Keep attachments under about 18MB.
What is the Outlook attachment size limit?
Outlook.com allows 25MB per email, text and attachments together. The Outlook desktop app limits Outlook.com, Gmail and other internet accounts to 20MB. Microsoft 365 business mailboxes default to 35MB for sending and 36MB for receiving, which an administrator can change.
How do I send large files by email?
Shrink them to about three-quarters of the limit — compress the video to a set size in MB, compress PDFs and Office files, resize photos — or send a Google Drive or OneDrive link. For a long PDF, split it into parts under a set size and send one per email.