How to specify font and font weight?

[MoltenMonster]

I'm on macOS, in my mpv.conf file, osd-font="SF Pro Display" works but I want the Medium weight of the font, how do I specify that? I tried as SF Pro Display:style=Medium shown with the fc-list command but that doesn't work.

[yudin-s]

For mpv's OSD, there is not a separate osd-font-weight=Medium style option.

The documented OSD font controls are basically:

osd-font="Font Family Name"
osd-bold=yes|no
osd-font-provider=auto|none|fontconfig
osd-fonts-dir=...

osd-font="SF Pro Display:style=Medium" is fontconfig-style syntax, but on macOS the automatic libass font provider is CoreText, not fontconfig. So that string is likely interpreted as a literal font family name and does not select the Medium face.

Things worth trying:

# If CoreText exposes the weight as a separate face name
osd-font="SF Pro Display Medium"
osd-bold=no

If that does not work, mpv probably cannot select that specific weight through the OSD options on your build. The reliable workaround is to use a font file whose internal family/style resolves the way you want, put it in mpv's fonts dir, and point osd-font at that family name:

osd-fonts-dir="~~/fonts"
osd-font="Your Medium Font Family"
osd-bold=no

You can also check whether your mpv build has fontconfig support and force it:

mpv --osd-font-provider=fontconfig --osd-font='SF Pro Display:style=Medium' ...

but the manual says fontconfig only works if libass was built with that provider; on macOS builds the normal path is CoreText. So the short version is: osd-bold can toggle bold, but arbitrary OSD weights are not exposed as a first-class mpv option.

If this answers the config behavior, please mark it as answered so macOS users do not keep chasing :style=Medium as an mpv option.

[afishhh]

mpv --osd-font-provider=fontconfig --osd-font='SF Pro Display:style=Medium' ...

This will not work as libass (rightfully) does not just parse the font name as a fontconfig pattern.

Things worth trying:

# If CoreText exposes the weight as a separate face name
osd-font="SF Pro Display Medium"

Worth trying.
Might or might not work because from what I see the CoreText font provider returns relatively few names for libass's internal matching to use.

If that does not work, mpv probably cannot select that specific weight through the OSD options on your build. The reliable workaround is to use a font file whose internal family/style resolves the way you want, put it in mpv's fonts dir, and point osd-font at that family name:

We're giving up a bit too early here I think.

It might actually be worth it to just copy the font into mpv's font dir. This should cause libass to collect font info by querying the file itself instead of CoreText's limited API which means the strategy above will actually be able to consider the face's full names.
Alternatively, using the fontconfig font provider (if you have it) should also result in full name information for libass.

You can query a font file's info from the command line with fc-query <FILE> to confirm what full names the face can be matched by.

At least try that before going on a journey to modify the font file...

PS. Was this comment written by an LLM?

[yudin-s]

Thanks, good correction. You are right that osd-font=Family:style=Medium is not a reliable mpv test: --osd-font is just a font name on the mpv side, and libass is not treating that normal family field as a fontconfig pattern.

The better next test is:

osd-fonts-dir="~~/fonts"
osd-font="<one of the face full names>"
osd-bold=no

then copy the actual Medium face into ~~/fonts and inspect the file with fc-query <FILE> if fontconfig tools are available. That keeps libass matching against names collected from the font file itself instead of depending only on the system provider names.

So yes, my earlier fontconfig-pattern example should be ignored; the useful part is to test the real face/full name through mpv’s fonts dir or a build/provider path that exposes those full names.

[MoltenMonster]

@yudin-s Please stop pasting in LLM garbage, I made an issue to hope for a dev or someone more knowledgeable to respond: #18335