Use qBittorrent’s magnet `so` parameter to preselect files

The magnet-link so parameter means select-only: it tells a compatible client which files within a torrent to download. qBittorrent added support in 5.3.0, released October 19, 2026, according to its official changelog.

For a lawful multi-file download—such as an open dataset—you can append &so=0,2,4,6-8 to the existing magnet link to preselect a subset. The client still needs the torrent’s metadata before it can resolve those numbers to actual files.

Syntax: indexes, not filenames

BEP 53 describes so as an optional list of file indexes, using commas to separate entries and hyphens for ranges. It remains a Draft proposal, although qBittorrent now supports it.

Examples of suffixes to append to an existing magnet URI:

Indexes are zero-based, and range endpoints are inclusive. The libtorrent 2.1.2 parser uses these numbers to assign download priorities, leaving unselected files at “do not download.”

Keep the existing magnet’s hash and other parameters intact. Add one so field, or replace its existing value if it already has one. Use plain decimal numbers, commas and hyphens, without spaces; that parser ignores the so field if its value contains other characters, rather than rejecting the whole magnet link.

so does not accept a filename, folder path or wildcard. Selecting a folder means listing the indexes of the files inside it. Nor does changing the display-name parameter dn select a file: BEP 9 defines dn as a name the client may display while waiting for metadata.

How to use it in qBittorrent

1. Check the qBittorrent version. Use 5.3.0 or a later release with this support; do not rely on older versions to honor the selection.
2. Confirm the target indexes. Obtain them from the torrent’s metadata or a trustworthy publisher’s file-index mapping. Do not infer them from an alphabetically sorted file display.
3. Append the selection suffix to the publisher’s magnet link—for example, &so=0,2 for indexes 0 and 2.
4. Open the edited link in qBittorrent’s desktop Add New Torrent dialog. Wait for metadata so you can review the file list.
5. Check the selected files before accepting the download. Correct the selection manually if the filenames do not match your intention.

The qBittorrent implementation carries the magnet’s file priorities into the desktop add dialog’s content tree. It also maps libtorrent’s native file indexes to qBittorrent’s displayed files. That matters because internal padding files can make simply counting visible rows unreliable.

If you are adding a batch remotely, see our guide to adding multiple magnets in qBittorrent WebUI. Verify each torrent’s resulting file selection rather than assuming a shared batch setting defines its subset.

If the selection does not work

Stuck retrieving metadata: so is a selection instruction, not a metadata source. BEP 9 describes retrieving torrent metadata from peers; adding file indexes cannot make unavailable metadata appear. See how a magnet link finds the file for the underlying discovery process.

The wrong files are selected: Check for one-based numbering, indexes copied from another torrent, or indexes guessed from the displayed sort order. The mapping belongs to that specific torrent’s metadata.

Everything is selected: Check the client version and the exact so value. Remove spaces, filenames and other unsupported characters, then inspect the resulting priorities.

The torrent is already in qBittorrent: Change its file selection directly in the Content tab. BEP 53 recommends enabling newly requested files when a magnet is added again; it does not describe replacing the existing selection wholesale. Do not treat reopening a modified magnet as a reliable reset of an existing torrent’s priorities.