iOS does not support fonts the same way other operating systems do. Maintaining look and feel across desktop and mobile installations of Obsidian means either using the standard fonts, or the conversion workaround below. It should work for Android as well, and technically anywhere you cannot install a font directly to the operating system where Obsidian is running.
- Source the font you want in either TTF or WOFF2 format. My preferred font is Noto Sans.
- Encode the font into base-64 format. This is necessary to bypass the inability to add an iOS font. Woff2Base works well and creates the CSS you need for the next step. Just select your TTF or WOFF2 file.
- Copy the CSS generated by Woff2Base and save it to a file called
fonts.cssin your Obsidian vault under.obsidian/snippets/. You can call the file anything you like, and even add it to your existing custom CSS. The most important piece is saving it in the snippets folder so Obsidian can find it. - Open Obsidian and go to
Settings > Appearance > CSS Snippetsand enablefonts.css. If Obsidian was already open you can refresh the list of CSS Snippets, then enable. - Sync to your mobile device. You may need to close and reopen Obsidian on your iPhone or iPad once the sync has completed and/or complete step 4 on that device as well.
Source: Adding a custom font to Android/iOS - Share & showcase - Obsidian Forum