"Maximum file size" pages are easy to find and hard to trust. Most of them copy each other, few say where a number came from, and platforms change their limits without telling the pages that quote them. This table is different in one way that matters: every figure was read from the service's own help page or official announcement, the source is linked next to it, and the date it was last checked is written at the top. We recheck it monthly.
Last checked: 24 September 2026. If a service has changed its limit since then, the linked source is the one to believe.
| Service | Attachment limit | What happens above it | Source |
|---|---|---|---|
| Gmail (personal) | 25 MB | Gmail removes the attachment and inserts a Google Drive link instead | Gmail Help |
| Gmail (work or school) | Set by your administrator | Varies | Gmail Help |
| Outlook.com | 25 MB; OneDrive attachments up to 2 GB | Share from OneDrive instead | Microsoft Support |
| Yahoo Mail | 25 MB, all attachments in one message together, incoming and outgoing | Message is refused | Yahoo Help |
| iCloud Mail with Mail Drop | Mail Drop: up to 5 GB per message; links expire after 30 days | Mail offers Mail Drop for large attachments | Apple Support |
Why a 25 MB limit fits an 18 MB file
Email was designed for text, so an attached file travels encoded as Base64: every three bytes become four characters, and a line break is added every 76 characters. We encoded a million random bytes the way mail programs do and measured the result: the attachment grew by 35.1%. Microsoft's own documentation for Exchange describes the same effect, saying a 64 MB message limit allows a realistic maximum of about 48 MB (Microsoft Learn).
| Limit on the encoded message | Largest file that fits, roughly |
|---|---|
| 25 MB | 18.3 MB |
| 20 MB | 14.6 MB |
Not every provider applies its limit to the encoded size, and none of them publish exactly how they count. The practical rule is simple: if a file is within a quarter of an email limit, expect trouble. Send a link, or make the file smaller first.
Chat and messaging
| Service | Limit per file | Source |
|---|---|---|
| 2 GB per file (raised from 100 MB in May 2022) | WhatsApp Blog | |
| Slack | 1 GB | Slack |
| Telegram | 2 GB; 4 GB with Premium | Telegram FAQ |
On WhatsApp, the 2 GB figure applies to files. Photos picked from the gallery are compressed before sending, which is a separate question from the limit. If the photo needs to arrive sharp, send it as a document, or size it yourself first with compress image for WhatsApp.
Discord is not in this table on purpose. Its free upload limit has changed more than once recently, and its help centre could not be read by our checker on the day we updated this page. Rather than copy a number we could not confirm, we keep the tiers on our Discord image page, where they are reviewed separately.
Passport and visa photos
These are the limits most likely to get an application rejected, because they have a minimum as well as a maximum, and some are measured in kilobytes, not megabytes.
| Application | File size | Pixels | Format | Source |
|---|---|---|---|---|
| US passport, online renewal | 54 KB to 10 MB | — | JPG, JPEG, PNG, HEIC or HEIF | travel.state.gov |
| US visa (DS-160, DS-1648) | 240 kB or less; compression ratio 20:1 or less | Square, 600×600 to 1200×1200 | JPEG, sRGB colour | travel.state.gov |
| US Diversity Visa (DV) entry | 240 kB or less | Square, 600×600 | JPEG | travel.state.gov |
| UK passport, digital photo | 50 KB to 10 MB | At least 600 wide and 750 tall | — | GOV.UK |
Two details catch people out. First, the minimums: a photo compressed too hard can fall under 54 KB or 50 KB and be refused for being too small, which is rarely what anyone expects. Second, the US visa limit is written as 240 kB, with a lower-case k. In standard units that is 240,000 bytes, not 245,760. A file that one program reports as "240 KB" may be over the limit by the other definition. We measured how wide that gap is, and which tools land in it, in why a 500 KB file fails a 500 KB limit.
The State Department pages are protected against automated access, so for the three US rows we read the most recent archived copies (all made in July 2026) and checked them against each other. If you are applying, open the linked page on the day, because it is the one the reviewer will follow.
How to get a file under a limit
The right move depends on what kind of file it is.
- A photo over a KB or MB limit: set the target size directly, a little under the number you were given, with compress image to a target size. For the US visa limit, compress to 200 KB leaves a safe margin.
- A photo that must also meet pixel rules: use the US or UK passport photo maker, which crop to the required proportions first and keep the file inside both the minimum and the maximum.
- A PDF over an email or portal limit: scanned and image-heavy PDFs shrink the most. Compress PDF resizes the images inside the pages and keeps text selectable, and lets you compare pages before you download.
- Anything close to an email limit: leave a quarter of the limit free for the encoding described above, or send a link.
All of these run in your browser, so the file you are trying to send is never uploaded somewhere else first. That matters more than usual for passport photos and application documents.
Why this page is dated
Limits move. WhatsApp went from 100 MB to 2 GB in one update. Discord has changed its free tier more than once. Government portals change their photo rules with little notice. A size table without a date is a guess about the past, so this one carries the date it was checked, a link for every number, and a note when a number could not be confirmed. If you find a figure here that no longer matches its source, tell us at hello@filewhisk.com and we will correct it the same day.