WordPress Multisite Max Upload File Size: The Hidden Cap

A WordPress Multisite network carries its own upload ceiling that has nothing to do with your PHP configuration. The Network Admin settings screen has a "Max upload file size" field, and WordPress's own Advanced Administration Handbook documents its default as 1500 KB — about 1.5 megabytes.

That is the detail almost every "increase your WordPress upload limit" article misses. On a single-site install, the number in the media uploader comes from PHP. On Multisite there is a second, much smaller number stored by the network itself, and it is the one people spend an afternoon failing to raise by editing php.ini.

The limits, at a glance

Every value below is quoted from WordPress's official documentation. Where the docs give no number, the cell says so rather than guessing.

The Upload Settings section of the Network Admin Settings Screen page is worth reading verbatim. Note that only one of the two lines is documented as a default:

"Site upload space Limit total size of files uploaded to [ 50 ] MB."

"Max upload file size Default is [ 1500 ] KB."

Two different things are being capped there. Site upload space is a running total per site; max upload file size applies to one file at a time.

Why there are two ceilings

On any WordPress install, the figure shown under the media uploader comes from the host, not from WordPress. The Media Add New screen documentation puts it plainly:

"You will also see a message displayed at the bottom of your view that indicates maximum upload size for files, as set by your hosting provider."

The core function behind that message, wp_max_upload_size(), is described as: "Determines the maximum upload size allowed in php.ini." Its body takes min() of two PHP values — upload_max_filesize and post_max_size — and passes the result through the upload_size_limit filter. So on the PHP side, the smaller of the two directives is what applies, and neither number lives in your WordPress database.

The PHP Optimization handbook page describes each directive directly: "The limit on the size of individual file uploads can be configured using the upload_max_filesize php.ini directive", while post_max_size governs "the entire size of a request that can be sent from the web server to PHP for processing". It also warns about the environment most Multisite networks actually run in: "Bear in mind that on shared hosting accounts, those limits are usually set on a server level and you may not be able to modify them or increase them above a certain value."

Multisite stacks a network-level setting on top of all that. WordPress's documentation does not state how the 1500 KB network field and the php.ini values combine — there is no official "the lower one wins" sentence, so do not treat any rule of thumb you read elsewhere as official. What the docs do establish is that both settings exist and that the network one ships at 1500 KB.

What to do when you hit it

Work through these in order.

1. Check the network field first. Open Network Admin, Settings, and look at Upload Settings. If the box still reads the documented default, raising PHP limits will change nothing.
2. Check site upload space for that specific site. A site can be under the per-file cap and still be out of room against its total.
3. Then look at PHP. Remember post_max_size must be greater than or equal to upload_max_filesize, and on shared hosting you may not be able to change either.
4. Or make the file smaller. This is the only step that needs no server access at all, and for video it is usually the fastest route to a working upload.

Video is usually what pushes a file past a 1500 KB ceiling, and step 4 is the only one on this list you can do without network-admin or server access. If you are troubleshooting somebody else's network, it is also the only one you can do today.

Try it right here

Runs in your browser. Your file is not uploaded anywhere.

Loading tool…

This runs inside your browser tab — the file is read from disk, re-encoded locally, and handed back. Nothing is uploaded to a server on the way to fixing an upload problem. WordPress.com's own upload troubleshooting page gives the same advice for its hosted sites: "Consider compressing your files and only uploading the size you need." The rest of the browser-side toolkit is at all Clapr tools, and the compressor itself lives at compress video.

Multisite-specific gotchas

The file-type list is a separate gate. Network Admin has an "Upload file types" field, and it does not work the way its name suggests. The official note is explicit: "Adding mime types in the 'upload file types' field not listed in the default set will NOT work unless you've added them using the upload_mimes filter! Uploading files with mime types not supported (without adding them using the filter) will fail with the message "Sorry, this file type is not permitted for security reasons"."

So if your upload fails with that exact wording, it is a type problem, not a size problem, and no amount of raising limits will help.

You cannot look up the default type list in the docs. WordPress says so itself: "The exact set of extensions varies between WordPress versions as new types are added; to see the current default for your installation, check the upload_filetypes value in the wp_sitemeta table or inspect wp_get_mime_types() in WordPress core."

Multisite's memory default is different. Per the handbook, "WordPress default is 40 MB and WordPress MultiSite default is 64 MB" for WP_MEMORY_LIMIT, with a separate backend limit — and the docs tie that backend limit straight to uploads: "This is mainly required for media uploads."

Upload duration has its own directive. max_execution_time gets all the attention, but the handbook says max_input_time "is usually used to limit the amount of time allowed to upload files", and notes that this time is "separate from max_execution_time". A large file that dies partway through may be hitting that instead of a size cap.

FAQ

What is the max upload file size on WordPress Multisite? The Network Admin Settings Screen documentation lists "Max upload file size" with "Default is [ 1500 ] KB." That is the shipped network default; whoever set up your network may have changed it.

Why does raising upload_max_filesize not work on Multisite? Because the network has its own Max upload file size field in addition to PHP's directives. WordPress's documentation does not state which one takes precedence, so check both rather than assuming php.ini is the whole story.

What is "Site upload space" and how is it different? It is the total, documented as "Limit total size of files uploaded to [ 50 ] MB." Max upload file size limits one file; site upload space limits everything a site has accumulated.

I get "Sorry, this file type is not permitted for security reasons" — is my file too big? No. That message comes from the file-type gate, and the official note says adding a type in the Upload file types field will not work unless it is also added through the upload_mimes filter.

Does WordPress have a documented default upload size for single-site installs? No. The official pages only say the maximum is "as set by your hosting provider" and that wp_max_upload_size() reads php.ini. Any specific default figure you see quoted elsewhere is not from WordPress's documentation — check the official documentation for your own install's value.

---

Uploading captions alongside your video? WordPress's self-hosted Video block states that text tracks "are formatted in WebVTT format (.vtt files or Web Video Text Tracks)", so an SRT from your editor needs converting first — SRT to VTT does it in the browser. More platform caps are collected in the limits hub.

Quotes above are from WordPress's Advanced Administration Handbook, developer reference, and WordPress.com support pages, checked 16 September 2026. Defaults change between versions — verify against the official documentation before relying on them.